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65f8b80053
When ext4_xattr_block_set() decides to remove xattr block the following
race can happen:
CPU1 CPU2
ext4_xattr_block_set() ext4_xattr_release_block()
new_bh = ext4_xattr_block_cache_find()
lock_buffer(bh);
ref = le32_to_cpu(BHDR(bh)->h_refcount);
if (ref == 1) {
...
mb_cache_entry_delete();
unlock_buffer(bh);
ext4_free_blocks();
...
ext4_forget(..., bh, ...);
jbd2_journal_revoke(..., bh);
ext4_journal_get_write_access(..., new_bh, ...)
do_get_write_access()
jbd2_journal_cancel_revoke(..., new_bh);
Later the code in ext4_xattr_block_set() finds out the block got freed
and cancels reusal of the block but the revoke stays canceled and so in
case of block reuse and journal replay the filesystem can get corrupted.
If the race works out slightly differently, we can also hit assertions
in the jbd2 code.
Fix the problem by making sure that once matching mbcache entry is
found, code dropping the last xattr block reference (or trying to modify
xattr block in place) waits until the mbcache entry reference is
dropped. This way code trying to reuse xattr block is protected from
someone trying to drop the last reference to xattr block.
Reported-and-tested-by: Ritesh Harjani <ritesh.list@gmail.com>
CC: stable@vger.kernel.org
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.