Move the calculation of the location of the dirent tail into
initialize_dirent_tail(). Also prefix the function with ext4_ to fix
kernel namepsace polution.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Functions such as ext4_dirent_csum_verify() and ext4_dirent_csum_set()
don't actually operate on a directory entry, but a directory block.
And while they take a struct ext4_dir_entry *dirent as an argument, it
had better be the first directory at the beginning of the direct
block, or things will go very wrong.
Rename the following functions so that things make more sense, and
remove a lot of confusing casts along the way:
ext4_dirent_csum_verify -> ext4_dirblock_csum_verify
ext4_dirent_csum_set -> ext4_dirblock_csum_set
ext4_dirent_csum -> ext4_dirblock_csum
ext4_handle_dirty_dirent_node -> ext4_handle_dirty_dirblock
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
The largedir feature was intended to allow ext4 directories to have
unmapped directory blocks (e.g., directory holes). And so the
released e2fsprogs no longer enforces this for largedir file systems;
however, the corresponding change to the kernel-side code was not made.
This commit fixes this oversight.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Temporarily cache a casefolded version of the file name under lookup in
ext4_filename, to avoid repeatedly casefolding it. I got up to 30%
speedup on lookups of large directories (>100k entries), depending on
the length of the string under lookup.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Unicode 12.1.0.
-----BEGIN PGP SIGNATURE-----
iQEzBAABCAAdFiEEK2m5VNv+CHkogTfJ8vlZVpUNgaMFAlzg2qIACgkQ8vlZVpUN
gaPYfgf+IadtbeBYbKcHQzw8OZ9UxyGv7+Havs523XzhdceiflpOCe3lpSFYuX6w
0CtRIWEOqFzQLRHUlX/sRywYLvrvg3irDuYJGTzny9MfPEI+tVCkYi877PPAOOR3
4xay7dF63mcCpmhRxgw1fLx5I/hYpzrDnw5dGe7jjgU6SrR5FpE2GmEmbfBW087W
zAuRDkuTv03J791Kgpq4TAMNla9F2/oedq/2B0v43+TnKfYe1SEIDm3VusUvSfoI
++8CfRrRJ3D7vCmtFSuieFFb91HtHMqdv0gaad2cY1DfvJLVm7gP1uPL7QahA5Dq
VfhvFfqshqN9Jizr6BqP5GPOj2J9cw==
=QK+R
-----END PGP SIGNATURE-----
Merge tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
Pull ext4 fixes from Ted Ts'o:
"Some bug fixes, and an update to the URL's for the final version of
Unicode 12.1.0"
* tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
ext4: avoid panic during forced reboot due to aborted journal
ext4: fix block validity checks for journal inodes using indirect blocks
unicode: update to Unicode 12.1.0 final
unicode: add missing check for an error return from utf8lookup()
ext4: fix miscellaneous sparse warnings
ext4: unsigned int compared against zero
ext4: fix use-after-free in dx_release()
ext4: fix data corruption caused by overlapping unaligned and aligned IO
jbd2: fix potential double free
ext4: zero out the unused memory region in the extent tree block
The buffer_head (frames[0].bh) and it's corresping page can be
potentially free'd once brelse() is done inside the for loop
but before the for loop exits in dx_release(). It can be free'd
in another context, when the page cache is flushed via
drop_caches_sysctl_handler(). This results into below data abort
when accessing info->indirect_levels in dx_release().
Unable to handle kernel paging request at virtual address ffffffc17ac3e01e
Call trace:
dx_release+0x70/0x90
ext4_htree_fill_tree+0x2d4/0x300
ext4_readdir+0x244/0x6f8
iterate_dir+0xbc/0x160
SyS_getdents64+0x94/0x174
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Cc: stable@kernel.org
miscellaneous cleanups.
-----BEGIN PGP SIGNATURE-----
iQEzBAABCAAdFiEEK2m5VNv+CHkogTfJ8vlZVpUNgaMFAlzSEfQACgkQ8vlZVpUN
gaNKrQf+O4JCCc8jqhpvUcNr8+DJNhWYpvRo7yDXoWbAyA6eZHV2fTRX5Vw6T8bW
iQAj9ofkRnakOq6JvnaUyW8eAuRcqellF7HnwFwTxGOpZ1x3UPAV/roKutAhe8sT
9dA0VxjugBAISbL2AMQKRPYNuzV07D9As6wZRlPuliFVLLnuPG5SseHRhdn3tm1n
Jwyipu8P6BjomFtfHT25amISaWRx/uGpjTa1fmjwUxIC8EI6V9K6hKNCAUPsk/3g
m8zEBpBKSmPK66sFPGxddPNGYAyyFluUboQxB7DuSCF7J3cULO8TxRZbsW/5jaio
ZR8utWezuXnrI80vG/VtCMhqG3398Q==
=0Bak
-----END PGP SIGNATURE-----
Merge tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt
Pull fscrypt updates from Ted Ts'o:
"Clean up fscrypt's dcache revalidation support, and other
miscellaneous cleanups"
* tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt:
fscrypt: cache decrypted symlink target in ->i_link
vfs: use READ_ONCE() to access ->i_link
fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext
fscrypt: only set dentry_operations on ciphertext dentries
fs, fscrypt: clear DCACHE_ENCRYPTED_NAME when unaliasing directory
fscrypt: fix race allowing rename() and link() of ciphertext dentries
fscrypt: clean up and improve dentry revalidation
fscrypt: use READ_ONCE() to access ->i_crypt_info
fscrypt: remove WARN_ON_ONCE() when decryption fails
fscrypt: drop inode argument from fscrypt_get_ctx()
This patch implements the actual support for case-insensitive file name
lookups in ext4, based on the feature bit and the encoding stored in the
superblock.
A filesystem that has the casefold feature set is able to configure
directories with the +F (EXT4_CASEFOLD_FL) attribute, enabling lookups
to succeed in that directory in a case-insensitive fashion, i.e: match
a directory entry even if the name used by userspace is not a byte per
byte match with the disk name, but is an equivalent case-insensitive
version of the Unicode string. This operation is called a
case-insensitive file name lookup.
The feature is configured as an inode attribute applied to directories
and inherited by its children. This attribute can only be enabled on
empty directories for filesystems that support the encoding feature,
thus preventing collision of file names that only differ by case.
* dcache handling:
For a +F directory, Ext4 only stores the first equivalent name dentry
used in the dcache. This is done to prevent unintentional duplication of
dentries in the dcache, while also allowing the VFS code to quickly find
the right entry in the cache despite which equivalent string was used in
a previous lookup, without having to resort to ->lookup().
d_hash() of casefolded directories is implemented as the hash of the
casefolded string, such that we always have a well-known bucket for all
the equivalencies of the same string. d_compare() uses the
utf8_strncasecmp() infrastructure, which handles the comparison of
equivalent, same case, names as well.
For now, negative lookups are not inserted in the dcache, since they
would need to be invalidated anyway, because we can't trust missing file
dentries. This is bad for performance but requires some leveraging of
the vfs layer to fix. We can live without that for now, and so does
everyone else.
* on-disk data:
Despite using a specific version of the name as the internal
representation within the dcache, the name stored and fetched from the
disk is a byte-per-byte match with what the user requested, making this
implementation 'name-preserving'. i.e. no actual information is lost
when writing to storage.
DX is supported by modifying the hashes used in +F directories to make
them case/encoding-aware. The new disk hashes are calculated as the
hash of the full casefolded string, instead of the string directly.
This allows us to efficiently search for file names in the htree without
requiring the user to provide an exact name.
* Dealing with invalid sequences:
By default, when a invalid UTF-8 sequence is identified, ext4 will treat
it as an opaque byte sequence, ignoring the encoding and reverting to
the old behavior for that unique file. This means that case-insensitive
file name lookup will not work only for that file. An optional bit can
be set in the superblock telling the filesystem code and userspace tools
to enforce the encoding. When that optional bit is set, any attempt to
create a file name using an invalid UTF-8 sequence will fail and return
an error to userspace.
* Normalization algorithm:
The UTF-8 algorithms used to compare strings in ext4 is implemented
lives in fs/unicode, and is based on a previous version developed by
SGI. It implements the Canonical decomposition (NFD) algorithm
described by the Unicode specification 12.1, or higher, combined with
the elimination of ignorable code points (NFDi) and full
case-folding (CF) as documented in fs/unicode/utf8_norm.c.
NFD seems to be the best normalization method for EXT4 because:
- It has a lower cost than NFC/NFKC (which requires
decomposing to NFD as an intermediary step)
- It doesn't eliminate important semantic meaning like
compatibility decompositions.
Although:
- This implementation is not completely linguistic accurate, because
different languages have conflicting rules, which would require the
specialization of the filesystem to a given locale, which brings all
sorts of problems for removable media and for users who use more than
one language.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
->lookup() in an encrypted directory begins as follows:
1. fscrypt_prepare_lookup():
a. Try to load the directory's encryption key.
b. If the key is unavailable, mark the dentry as a ciphertext name
via d_flags.
2. fscrypt_setup_filename():
a. Try to load the directory's encryption key.
b. If the key is available, encrypt the name (treated as a plaintext
name) to get the on-disk name. Otherwise decode the name
(treated as a ciphertext name) to get the on-disk name.
But if the key is concurrently added, it may be found at (2a) but not at
(1a). In this case, the dentry will be wrongly marked as a ciphertext
name even though it was actually treated as plaintext.
This will cause the dentry to be wrongly invalidated on the next lookup,
potentially causing problems. For example, if the racy ->lookup() was
part of sys_mount(), then the new mount will be detached when anything
tries to access it. This is despite the mountpoint having a plaintext
path, which should remain valid now that the key was added.
Of course, this is only possible if there's a userspace race. Still,
the additional kernel-side race is confusing and unexpected.
Close the kernel-side race by changing fscrypt_prepare_lookup() to also
set the on-disk filename (step 2b), consistent with the d_flags update.
Fixes: 28b4c26396 ("ext4 crypto: revalidate dentry after adding or removing the key")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
In order to have a common code base for fscrypt "post read" processing
for all filesystems which support encryption, this commit removes
filesystem specific build config option (e.g. CONFIG_EXT4_FS_ENCRYPTION)
and replaces it with a build option (i.e. CONFIG_FS_ENCRYPTION) whose
value affects all the filesystems making use of fscrypt.
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit removes the ext4 specific ext4_encrypted_inode() and makes
use of the generic IS_ENCRYPTED() macro to check for the encryption
status of an inode.
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
If we receive a file handle, either from NFS or open_by_handle_at(2),
and it points at an inode which has not been initialized, and the file
system has metadata checksums enabled, we shouldn't try to get the
inode, discover the checksum is invalid, and then declare the file
system as being inconsistent.
This can be reproduced by creating a test file system via "mke2fs -t
ext4 -O metadata_csum /tmp/foo.img 8M", mounting it, cd'ing into that
directory, and then running the following program.
#define _GNU_SOURCE
#include <fcntl.h>
struct handle {
struct file_handle fh;
unsigned char fid[MAX_HANDLE_SZ];
};
int main(int argc, char **argv)
{
struct handle h = {{8, 1 }, { 12, }};
open_by_handle_at(AT_FDCWD, &h.fh, O_RDONLY);
return 0;
}
Google-Bug-Id: 120690101
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
error return cleanup paths.
-----BEGIN PGP SIGNATURE-----
iQEzBAABCAAdFiEEK2m5VNv+CHkogTfJ8vlZVpUNgaMFAlvoFrEACgkQ8vlZVpUN
gaMTSQf+Ogrvm7pfWtXf+RkmhhuyR26T+Hwxgl51m5bKetJBjEsh0qOaIfo7etwG
aLc1x/pWng2VTCHk4z0Ij9KS8YwLK3sQCBYZoJFyT/R09yGgAhLm+xP5j38WLqrX
h4GxVgekHSATkG95N/So7F7pQiz7gDowgbaYFW3PooXPoHJnCnTzcr7TGFAQBZAw
iR+8+KtH5E8IcC7Jj40nemk7Wib45DgaeGpP5P9Ct/Jw7hW+Mwhf56NYOWkLdHyy
4Kt7rm1Sbxam8k3nksNmIwx28bw+S0Ew1zZgkwgAcKcHaWdrv3TtGPkOA26AH+S3
UVeORM7xH+zXslIOyFK+7sXUZr5LiQ==
=BaBl
-----END PGP SIGNATURE-----
Merge tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
Pull ext4 fixes from Ted Ts'o:
"A large number of ext4 bug fixes, mostly buffer and memory leaks on
error return cleanup paths"
* tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
ext4: missing !bh check in ext4_xattr_inode_write()
ext4: fix buffer leak in __ext4_read_dirblock() on error path
ext4: fix buffer leak in ext4_expand_extra_isize_ea() on error path
ext4: fix buffer leak in ext4_xattr_move_to_block() on error path
ext4: release bs.bh before re-using in ext4_xattr_block_find()
ext4: fix buffer leak in ext4_xattr_get_block() on error path
ext4: fix possible leak of s_journal_flag_rwsem in error path
ext4: fix possible leak of sbi->s_group_desc_leak in error path
ext4: remove unneeded brelse call in ext4_xattr_inode_update_ref()
ext4: avoid possible double brelse() in add_new_gdb() on error path
ext4: avoid buffer leak in ext4_orphan_add() after prior errors
ext4: avoid buffer leak on shutdown in ext4_mark_iloc_dirty()
ext4: fix possible inode leak in the retry loop of ext4_resize_fs()
ext4: fix missing cleanup if ext4_alloc_flex_bg_array() fails while resizing
ext4: add missing brelse() update_backups()'s error path
ext4: add missing brelse() add_new_gdb_meta_bg()'s error path
ext4: add missing brelse() in set_flexbg_block_bitmap()'s error path
ext4: avoid potential extra brelse in setup_new_flex_group_blocks()
Pull misc vfs updates from Al Viro:
"No common topic, really - a handful of assorted stuff; the least
trivial bits are Mark's dedupe patches"
* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fs/exofs: only use true/false for asignment of bool type variable
fs/exofs: fix potential memory leak in mount option parsing
Delete invalid assignment statements in do_sendfile
iomap: remove duplicated include from iomap.c
vfs: dedupe should return EPERM if permission is not granted
vfs: allow dedupe of user owned read-only files
ntfs: don't open-code ERR_CAST
ext4: don't open-code ERR_CAST
Enabling DX_DEBUG triggers the build error below. info is an attribute
of the dxroot structure.
linux/fs/ext4/namei.c:2264:12: error: ‘info’
undeclared (first use in this function); did you mean ‘insl’?
info->indirect_levels));
Fixes: e08ac99fa2 ("ext4: add largedir feature")
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
If the destination of the rename(2) system call exists, the inode's
link count (i_nlinks) must be non-zero. If it is, the inode can end
up on the orphan list prematurely, leading to all sorts of hilarity,
including a use-after-free.
https://bugzilla.kernel.org/show_bug.cgi?id=200931
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reported-by: Wen Xu <wen.xu@gatech.edu>
Cc: stable@vger.kernel.org
When ext4_find_entry() falls back to "searching the old fashioned
way" due to a corrupt dx dir, it needs to reset the error code
to NULL so that the nonstandard ERR_BAD_DX_DIR code isn't returned
to userspace.
https://bugzilla.kernel.org/show_bug.cgi?id=199947
Reported-by: Anatoly Trosinenko <anatoly.trosinenko@yandex.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Pull the timespec64 conversion from Deepa Dinamani:
"The series aims to switch vfs timestamps to use
struct timespec64. Currently vfs uses struct timespec,
which is not y2038 safe.
The flag patch applies cleanly. I've not seen the timestamps
update logic change often. The series applies cleanly on 4.17-rc6
and linux-next tip (top commit: next-20180517).
I'm not sure how to merge this kind of a series with a flag patch.
We are targeting 4.18 for this.
Let me know if you have other suggestions.
The series involves the following:
1. Add vfs helper functions for supporting struct timepec64 timestamps.
2. Cast prints of vfs timestamps to avoid warnings after the switch.
3. Simplify code using vfs timestamps so that the actual
replacement becomes easy.
4. Convert vfs timestamps to use struct timespec64 using a script.
This is a flag day patch.
I've tried to keep the conversions with the script simple, to
aid in the reviews. I've kept all the internal filesystem data
structures and function signatures the same.
Next steps:
1. Convert APIs that can handle timespec64, instead of converting
timestamps at the boundaries.
2. Update internal data structures to avoid timestamp conversions."
I've pulled it into a branch based on top of the NFS changes that
are now in mainline, so I could resolve the non-obvious conflict
between the two while merging.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
For anything NFS-exported we do _not_ want to unlock new inode
before it has grown an alias; original set of fixes got the
ordering right, but missed the nasty complication in case of
lockdep being enabled - unlock_new_inode() does
lockdep_annotate_inode_mutex_key(inode)
which can only be done before anyone gets a chance to touch
->i_mutex. Unfortunately, flipping the order and doing
unlock_new_inode() before d_instantiate() opens a window when
mkdir can race with open-by-fhandle on a guessed fhandle, leading
to multiple aliases for a directory inode and all the breakage
that follows from that.
Correct solution: a new primitive (d_instantiate_new())
combining these two in the right order - lockdep annotate, then
d_instantiate(), then the rest of unlock_new_inode(). All
combinations of d_instantiate() with unlock_new_inode() should
be converted to that.
Cc: stable@kernel.org # 2.6.29 and later
Tested-by: Mike Marshall <hubcap@omnibond.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-----BEGIN PGP SIGNATURE-----
iQEzBAABCAAdFiEEK2m5VNv+CHkogTfJ8vlZVpUNgaMFAlp2R3AACgkQ8vlZVpUN
gaOIdAgApEdlFR2Gf93z2hMj5HxVL5rjkuPJVtVkKu0eH2HMQJyxNmjymrRfuFmM
8W1CrEvVKi5Aj6r8q4KHIdVV247Ya0SVEhLwKM0LX4CvlZUXmwgCmZ/MPDTXA1eq
C4vPVuJAuSNGNVYDlDs3+NiMHINGNVnBVQQFSPBP9P+iNWPD7o486712qaF8maVn
RbfbQ2rWtOIRdlAOD1U5WqgQku59lOsmHk2pc0+X4LHCZFpMoaO80JVjENPAw+BF
daRt6TX+WljMyx6DRIaszqau876CJhe/tqlZcCLOkpXZP0jJS13yodp26dVQmjCh
w8YdiY7uHK2D+S/8eyj7h7DIwzu3vg==
=ZjQP
-----END PGP SIGNATURE-----
Merge tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt
Pull fscrypt updates from Ted Ts'o:
"Refactor support for encrypted symlinks to move common code to fscrypt"
Ted also points out about the merge:
"This makes the f2fs symlink code use the fscrypt_encrypt_symlink()
from the fscrypt tree. This will end up dropping the kzalloc() ->
f2fs_kzalloc() change, which means the fscrypt-specific allocation
won't get tested by f2fs's kmalloc error injection system; which is
fine"
* tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt: (26 commits)
fscrypt: fix build with pre-4.6 gcc versions
fscrypt: remove 'ci' parameter from fscrypt_put_encryption_info()
fscrypt: document symlink length restriction
fscrypt: fix up fscrypt_fname_encrypted_size() for internal use
fscrypt: define fscrypt_fname_alloc_buffer() to be for presented names
fscrypt: calculate NUL-padding length in one place only
fscrypt: move fscrypt_symlink_data to fscrypt_private.h
fscrypt: remove fscrypt_fname_usr_to_disk()
ubifs: switch to fscrypt_get_symlink()
ubifs: switch to fscrypt ->symlink() helper functions
ubifs: free the encrypted symlink target
f2fs: switch to fscrypt_get_symlink()
f2fs: switch to fscrypt ->symlink() helper functions
ext4: switch to fscrypt_get_symlink()
ext4: switch to fscrypt ->symlink() helper functions
fscrypt: new helper function - fscrypt_get_symlink()
fscrypt: new helper functions for ->symlink()
fscrypt: trim down fscrypt.h includes
fscrypt: move fscrypt_is_dot_dotdot() to fs/crypto/fname.c
fscrypt: move fscrypt_valid_enc_modes() to fscrypt_private.h
...
-----BEGIN PGP SIGNATURE-----
iQEzBAABCAAdFiEEK2m5VNv+CHkogTfJ8vlZVpUNgaMFAlp16xMACgkQ8vlZVpUN
gaP1IAf8C48AKVnqy6ftFphzV1CdeGHDwJLL63lChs97fNr1mxo5TZE/6vdYB55j
k7C7huQ582cEiGWQJ0U4/+En0hF85zkAk5mTfnSao5BqxLr9ANsAocwBUNBXdFSp
B7IyMo4Dct7NCkwfmKLPRcEqZ49vwyv99TqM/9wUkgUStkTjPT7bhHgarB6VPbhp
BxoXVnFYgU0sZN0y71IBt8ngWqCK6j7fjw3gsl37oEenG3/h3SO0H9ih1FrysX8S
VOwwLJq6vfAgEwQvZACnBwWKDYsZpH7akNp9WGeDMByo28t514RNRjIi0mvLHEZa
h72I8Sb3bwHO9MJNvHFe/0b1Say4vw==
=dxAX
-----END PGP SIGNATURE-----
Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
Pull ext4 updates from Ted Ts'o:
"Only miscellaneous cleanups and bug fixes for ext4 this cycle"
* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
ext4: create ext4_kset dynamically
ext4: create ext4_feat kobject dynamically
ext4: release kobject/kset even when init/register fail
ext4: fix incorrect indentation of if statement
ext4: correct documentation for grpid mount option
ext4: use 'sbi' instead of 'EXT4_SB(sb)'
ext4: save error to disk in __ext4_grp_locked_error()
jbd2: fix sphinx kernel-doc build warnings
ext4: fix a race in the ext4 shutdown path
mbcache: make sure c_entry_count is not decremented past zero
ext4: no need flush workqueue before destroying it
ext4: fixed alignment and minor code cleanup in ext4.h
ext4: fix ENOSPC handling in DAX page fault handler
dax: pass detailed error code from dax_iomap_fault()
mbcache: revert "fs/mbcache.c: make count_objects() more robust"
mbcache: initialize entry->e_referenced in mb_cache_entry_create()
ext4: fix up remaining files with SPDX cleanups
-----BEGIN PGP SIGNATURE-----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=iihN
-----END PGP SIGNATURE-----
Merge tag 'iversion-v4.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux
Pull inode->i_version rework from Jeff Layton:
"This pile of patches is a rework of the inode->i_version field. We
have traditionally incremented that field on every inode data or
metadata change. Typically this increment needs to be logged on disk
even when nothing else has changed, which is rather expensive.
It turns out though that none of the consumers of that field actually
require this behavior. The only real requirement for all of them is
that it be different iff the inode has changed since the last time the
field was checked.
Given that, we can optimize away most of the i_version increments and
avoid dirtying inode metadata when the only change is to the i_version
and no one is querying it. Queries of the i_version field are rather
rare, so we can help write performance under many common workloads.
This patch series converts existing accesses of the i_version field to
a new API, and then converts all of the in-kernel filesystems to use
it. The last patch in the series then converts the backend
implementation to a scheme that optimizes away a large portion of the
metadata updates when no one is looking at it.
In my own testing this series significantly helps performance with
small I/O sizes. I also got this email for Christmas this year from
the kernel test robot (a 244% r/w bandwidth improvement with XFS over
DAX, with 4k writes):
https://lkml.org/lkml/2017/12/25/8
A few of the earlier patches in this pile are also flowing to you via
other trees (mm, integrity, and nfsd trees in particular)".
* tag 'iversion-v4.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux: (22 commits)
fs: handle inode->i_version more efficiently
btrfs: only dirty the inode in btrfs_update_time if something was changed
xfs: avoid setting XFS_ILOG_CORE if i_version doesn't need incrementing
fs: only set S_VERSION when updating times if necessary
IMA: switch IMA over to new i_version API
xfs: convert to new i_version API
ufs: use new i_version API
ocfs2: convert to new i_version API
nfsd: convert to new i_version API
nfs: convert to new i_version API
ext4: convert to new i_version API
ext2: convert to new i_version API
exofs: switch to new i_version API
btrfs: convert to new i_version API
afs: convert to new i_version API
affs: convert to new i_version API
fat: convert to new i_version API
fs: don't take the i_lock in inode_inc_iversion
fs: new API for handling inode->i_version
ntfs: remove i_version handling
...
Add a documentation blob that explains what the i_version field is, how
it is expected to work, and how it is currently implemented by various
filesystems.
We already have inode_inc_iversion. Add several other functions for
manipulating and accessing the i_version counter. For now, the
implementation is trivial and basically works the way that all of the
open-coded i_version accesses work today.
Future patches will convert existing users of i_version to use the new
API, and then convert the backend implementation to do things more
efficiently.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
The indentation is incorrect and spaces need replacing with a tab
on the if statement.
Cleans up smatch warning:
fs/ext4/namei.c:3220 ext4_link() warn: inconsistent indenting
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
On a ppc64 machine, when mounting a fuzzed ext2 image (generated by
fsfuzzer) the following call trace is seen,
VFS: brelse: Trying to free free buffer
WARNING: CPU: 1 PID: 6913 at /root/repos/linux/fs/buffer.c:1165 .__brelse.part.6+0x24/0x40
.__brelse.part.6+0x20/0x40 (unreliable)
.ext4_find_entry+0x384/0x4f0
.ext4_lookup+0x84/0x250
.lookup_slow+0xdc/0x230
.walk_component+0x268/0x400
.path_lookupat+0xec/0x2d0
.filename_lookup+0x9c/0x1d0
.vfs_statx+0x98/0x140
.SyS_newfstatat+0x48/0x80
system_call+0x58/0x6c
This happens because the directory that ext4_find_entry() looks up has
inode->i_size that is less than the block size of the filesystem. This
causes 'nblocks' to have a value of zero. ext4_bread_batch() ends up not
reading any of the directory file's blocks. This renders the entries in
bh_use[] array to continue to have garbage data. buffer_uptodate() on
bh_use[0] can then return a zero value upon which brelse() function is
invoked.
This commit fixes the bug by returning -ENOENT when the directory file
has no associated blocks.
Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
-----BEGIN PGP SIGNATURE-----
iQEzBAABCAAdFiEEK2m5VNv+CHkogTfJ8vlZVpUNgaMFAloI8AUACgkQ8vlZVpUN
gaMdjgf8CCW7UhPjoZYwF8sUNtAaX9+JZT1maOcXUhpJ3vRQiRn+AzRH6yBYMm79
+NZBwVlk4dlEe55Wh4yFIStMAstqzCrke4C9CSbExjgHNsJdU4znyYuLRMbLfyO0
6c4NObiAIKJdW1/te1aN90keGC6min8pBZot+FqZsRr+Kq2+IOtM43JAv7efOLev
v3LCjUf9JKxatoB8tgw4AJRa1p18p7D2APWTG05VlFq63TjhVIYNvvwcQlizLwGY
cuEq3X59FbFdX06fJnucujU3WP3ES4/3rhufBK4NNaec5e5dbnH2KlAx7J5SyMIZ
0qUFB/dmXDSb3gsfScSGo1F71Ad0CA==
=asAm
-----END PGP SIGNATURE-----
Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt
Pull fscrypt updates from Ted Ts'o:
"Lots of cleanups, mostly courtesy by Eric Biggers"
* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt:
fscrypt: lock mutex before checking for bounce page pool
fscrypt: add a documentation file for filesystem-level encryption
ext4: switch to fscrypt_prepare_setattr()
ext4: switch to fscrypt_prepare_lookup()
ext4: switch to fscrypt_prepare_rename()
ext4: switch to fscrypt_prepare_link()
ext4: switch to fscrypt_file_open()
fscrypt: new helper function - fscrypt_prepare_setattr()
fscrypt: new helper function - fscrypt_prepare_lookup()
fscrypt: new helper function - fscrypt_prepare_rename()
fscrypt: new helper function - fscrypt_prepare_link()
fscrypt: new helper function - fscrypt_file_open()
fscrypt: new helper function - fscrypt_require_key()
fscrypt: remove unneeded empty fscrypt_operations structs
fscrypt: remove ->is_encrypted()
fscrypt: switch from ->is_encrypted() to IS_ENCRYPTED()
fs, fscrypt: add an S_ENCRYPTED inode flag
fscrypt: clean up include file mess
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ext4_xattr_inode_read() currently reads each block sequentially while
waiting for io operation to complete before moving on to the next
block. This prevents request merging in block layer.
Add a ext4_bread_batch() function that starts reads for all blocks
then optionally waits for them to complete. A similar logic is used
in ext4_find_entry(), so update that code to use the new function.
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
The dir_nlink feature has been enabled by default for new ext4
filesystems since e2fsprogs-1.41 in 2008, and was automatically
enabled by the kernel for older ext4 filesystems since the
dir_nlink feature was added with ext4 in kernel 2.6.28+ when
the subdirectory count exceeded EXT4_LINK_MAX-1.
Automatically adding the file system features such as dir_nlink is
generally frowned upon, since it could cause the file system to not be
mountable on older kernel, thus preventing the administrator from
rolling back to an older kernel if necessary.
In this case, the administrator might also want to disable the feature
because glibc's fts_read() function does not correctly optimize
directory traversal for directories that use st_nlinks field of 1 to
indicate that the number of links in the directory are not tracked by
the file system, and could fail to traverse the full directory
hierarchy. Fortunately, in the past ten years very few users have
complained about incomplete file system traversal by glibc's
fts_read().
This commit also changes ext4_inc_count() to allow i_nlinks to reach
the full EXT4_LINK_MAX links on the parent directory (including "."
and "..") before changing i_links_count to be 1.
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196405
Signed-off-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Previously a bad directory block with a bad checksum is skipped; we
should be returning EFSBADCRC (aka EBADMSG).
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Previously, a read error would be ignored and we would eventually return
NULL from ext4_find_entry, which signals "no such file or directory". We
should be returning EIO.
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
This INCOMPAT_LARGEDIR feature allows larger directories to be created
in ldiskfs, both with directory sizes over 2GB and and a maximum htree
depth of 3 instead of the current limit of 2. These features are needed
in order to exceed the current limit of approximately 10M entries in a
single directory.
This patch was originally written by Yang Sheng to support the Lustre server.
[ Bumped the credits needed to update an indexed directory -- tytso ]
Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Signed-off-by: Artem Blagodarenko <artem.blagodarenko@seagate.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Now that we are passing a struct ext4_filename, we do not need to pass
around the original struct qstr too.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
-----BEGIN PGP SIGNATURE-----
iQEzBAABCAAdFiEEK2m5VNv+CHkogTfJ8vlZVpUNgaMFAlkPYHkACgkQ8vlZVpUN
gaM97ggAlOm8n/tlbcdonX/+HHjlnqcy5uYD7A9AH/JordpRzy4eqcMbxMG39p1R
DBtjo9Y0i3iFEGajRc0h7KXDLeTBUQ/JZpR8H60MFfAQHnTowuI91eb3/6QeZiHh
CN/2KKzpYitPIEUfEHnVeYKOfvrzR7je5hrEiAwEkPeKv7XyrNVM0LHQ/jKpbQwg
ntIzHvxjQyo8plx/m5S4Yew7tqjYpNiq4plmyk/Vxtw2FmB/FC76UxYeadoB3EI5
etw+bCORB0tFZO27o56kXywg+mDcp7HEtVvq9LG28oEuBDAVKNoeKEvV7SiOBlZp
+HnqIz5Hx1UTxOlTAc10IjvEhriEuw==
=qCDl
-----END PGP SIGNATURE-----
Merge tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt
Pull fscrypt updates from Ted Ts'o:
"Only bug fixes and cleanups for this merge window"
* tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt:
fscrypt: correct collision claim for digested names
MAINTAINERS: fscrypt: update mailing list, patchwork, and git
ext4: clean up ext4_match() and callers
f2fs: switch to using fscrypt_match_name()
ext4: switch to using fscrypt_match_name()
fscrypt: introduce helper function for filename matching
fscrypt: avoid collisions when presenting long encrypted filenames
f2fs: check entire encrypted bigname when finding a dentry
ubifs: check for consistent encryption contexts in ubifs_lookup()
f2fs: sync f2fs_lookup() with ext4_lookup()
ext4: remove "nokey" check from ext4_lookup()
fscrypt: fix context consistency check when key(s) unavailable
fscrypt: Remove __packed from fscrypt_policy
fscrypt: Move key structure and constants to uapi
fscrypt: remove fscrypt_symlink_data_len()
fscrypt: remove unnecessary checks for NULL operations
When ext4 encryption was originally merged, we were encrypting the
user-specified filename in ext4_match(), introducing a lot of additional
complexity into ext4_match() and its callers. This has since been
changed to encrypt the filename earlier, so we can remove the gunk
that's no longer needed. This more or less reverts ext4_search_dir()
and ext4_find_dest_de() to the way they were in the v4.0 kernel.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Switch ext4 directory searches to use the fscrypt_match_name() helper
function. There should be no functional change.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
When accessing an encrypted directory without the key, userspace must
operate on filenames derived from the ciphertext names, which contain
arbitrary bytes. Since we must support filenames as long as NAME_MAX,
we can't always just base64-encode the ciphertext, since that may make
it too long. Currently, this is solved by presenting long names in an
abbreviated form containing any needed filesystem-specific hashes (e.g.
to identify a directory block), then the last 16 bytes of ciphertext.
This needs to be sufficient to identify the actual name on lookup.
However, there is a bug. It seems to have been assumed that due to the
use of a CBC (ciphertext block chaining)-based encryption mode, the last
16 bytes (i.e. the AES block size) of ciphertext would depend on the
full plaintext, preventing collisions. However, we actually use CBC
with ciphertext stealing (CTS), which handles the last two blocks
specially, causing them to appear "flipped". Thus, it's actually the
second-to-last block which depends on the full plaintext.
This caused long filenames that differ only near the end of their
plaintexts to, when observed without the key, point to the wrong inode
and be undeletable. For example, with ext4:
# echo pass | e4crypt add_key -p 16 edir/
# seq -f "edir/abcdefghijklmnopqrstuvwxyz012345%.0f" 100000 | xargs touch
# find edir/ -type f | xargs stat -c %i | sort | uniq | wc -l
100000
# sync
# echo 3 > /proc/sys/vm/drop_caches
# keyctl new_session
# find edir/ -type f | xargs stat -c %i | sort | uniq | wc -l
2004
# rm -rf edir/
rm: cannot remove 'edir/_A7nNFi3rhkEQlJ6P,hdzluhODKOeWx5V': Structure needs cleaning
...
To fix this, when presenting long encrypted filenames, encode the
second-to-last block of ciphertext rather than the last 16 bytes.
Although it would be nice to solve this without depending on a specific
encryption mode, that would mean doing a cryptographic hash like SHA-256
which would be much less efficient. This way is sufficient for now, and
it's still compatible with encryption modes like HEH which are strong
pseudorandom permutations. Also, changing the presented names is still
allowed at any time because they are only provided to allow applications
to do things like delete encrypted directories. They're not designed to
be used to persistently identify files --- which would be hard to do
anyway, given that they're encrypted after all.
For ease of backports, this patch only makes the minimal fix to both
ext4 and f2fs. It leaves ubifs as-is, since ubifs doesn't compare the
ciphertext block yet. Follow-on patches will clean things up properly
and make the filesystems use a shared helper function.
Fixes: 5de0b4d0cd ("ext4 crypto: simplify and speed up filename encryption")
Reported-by: Gwendal Grignou <gwendal@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Now that fscrypt_has_permitted_context() correctly handles the case
where we have the key for the parent directory but not the child, we
don't need to try to work around this in ext4_lookup().
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
In the initial implementation of ext4 encryption, the filename was
encrypted in ext4_insert_dentry(), which could fail and also required
access to the 'dir' inode. Since then ext4 filename encryption has been
changed to encrypt the filename earlier, so we can revert the additions
to ext4_insert_dentry().
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
