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Iulia Manda 2813893f8b kernel: conditionally support non-root users, groups and capabilities 
There are a lot of embedded systems that run most or all of their
functionality in init, running as root:root.  For these systems,
supporting multiple users is not necessary.

This patch adds a new symbol, CONFIG_MULTIUSER, that makes support for
non-root users, non-root groups, and capabilities optional.  It is enabled
under CONFIG_EXPERT menu.

When this symbol is not defined, UID and GID are zero in any possible case
and processes always have all capabilities.

The following syscalls are compiled out: setuid, setregid, setgid,
setreuid, setresuid, getresuid, setresgid, getresgid, setgroups,
getgroups, setfsuid, setfsgid, capget, capset.

Also, groups.c is compiled out completely.

In kernel/capability.c, capable function was moved in order to avoid
adding two ifdef blocks.

This change saves about 25 KB on a defconfig build.  The most minimal
kernels have total text sizes in the high hundreds of kB rather than
low MB.  (The 25k goes down a bit with allnoconfig, but not that much.

The kernel was booted in Qemu.  All the common functionalities work.
Adding users/groups is not possible, failing with -ENOSYS.

Bloat-o-meter output:
add/remove: 7/87 grow/shrink: 19/397 up/down: 1675/-26325 (-24650)

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Iulia Manda <iulia.manda21@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-15 16:35:22 -07:00
..
9p Merge branch 'iocb' into for-next 2015-04-11 22:24:41 -04:00
adfs
affs Merge branch 'for-linus-1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-14 15:31:03 -07:00
afs Merge remote-tracking branch 'dh/afs' into for-davem 2015-04-11 15:51:09 -04:00
autofs4 autofs4 copy_dev_ioctl(): keep the value of ->size we'd used for allocation 2015-02-22 11:43:34 -05:00
befs fs/befs/linuxvfs.c: remove unnecessary casting 2015-02-17 14:34:50 -08:00
bfs fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
btrfs Merge branch 'iocb' into for-next 2015-04-11 22:24:41 -04:00
cachefiles Cachefiles: Fix up scripted S_ISDIR/S_ISREG/S_ISLNK conversions 2015-02-22 11:38:41 -05:00
ceph Merge branch 'iocb' into for-next 2015-04-11 22:24:41 -04:00
cifs mm, mempool: do not allow atomic resizing 2015-04-14 16:49:06 -07:00
coda VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry) 2015-02-22 11:38:41 -05:00
configfs configfs: Fix potential NULL d_inode dereference 2015-02-20 04:56:43 -05:00
cramfs
debugfs debugfs: allow bad parent pointers to be passed in 2015-04-03 16:30:12 +02:00
devpts
dlm netlink: make nlmsg_end() and genlmsg_end() void 2015-01-18 01:03:45 -05:00
ecryptfs Merge branch 'iocb' into for-next 2015-04-11 22:24:41 -04:00
efivarfs * Move efivarfs from the misc filesystem section to pseudo filesystem, 2015-01-29 19:16:40 +01:00
efs
exofs vfs: remove get_xip_mem 2015-02-16 17:56:03 -08:00
exportfs VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry) 2015-02-22 11:38:41 -05:00
ext2 dax: unify ext2/4_{dax,}_file_operations 2015-04-15 16:35:20 -07:00
ext3 fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
ext4 dax: unify ext2/4_{dax,}_file_operations 2015-04-15 16:35:20 -07:00
f2fs fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
fat fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
freevxfs
fscache fs/fscache/object-list.c: use __seq_open_private() 2014-10-13 17:52:21 +01:00
fuse Merge branch 'iocb' into for-next 2015-04-11 22:24:41 -04:00
gfs2 GFS2: merge window 2015-04-14 16:09:18 -07:00
hfs fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
hfsplus Merge branch 'for-linus-1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-14 15:31:03 -07:00
hostfs
hpfs
hppfs VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry) 2015-02-22 11:38:41 -05:00
hugetlbfs hugetlbfs: accept subpool min_size mount option and setup accordingly 2015-04-15 16:35:18 -07:00
isofs isofs: Fix bug in the way to check if the year is a leap year 2015-01-07 09:51:49 +01:00
jbd jbd: Deletion of an unnecessary check before the function call "iput" 2014-11-18 10:15:29 +01:00
jbd2 jbd2: complain about descriptor block checksum errors 2015-01-19 15:59:58 -05:00
jffs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2015-04-14 09:50:27 -07:00
jfs fs, jfs: remove slab object constructor 2015-04-15 16:35:18 -07:00
kernfs kernfs: handle poll correctly on 'direct_read' files. 2015-03-16 21:51:20 +01:00
lockd Merge branch 'for-3.20' of git://linux-nfs.org/~bfields/linux 2015-02-12 10:39:41 -08:00
logfs
minix
ncpfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-02-17 14:56:45 -08:00
nfs kernel: conditionally support non-root users, groups and capabilities 2015-04-15 16:35:22 -07:00
nfs_common
nfsd kernel: conditionally support non-root users, groups and capabilities 2015-04-15 16:35:22 -07:00
nilfs2 Merge branch 'iocb' into for-next 2015-04-11 22:24:41 -04:00
nls
notify fanotify: fix event filtering with FAN_ONDIR set 2015-03-12 18:46:08 -07:00
ntfs Merge branch 'iocb' into for-next 2015-04-11 22:24:41 -04:00
ocfs2 Merge branch 'akpm' (patches from Andrew) 2015-04-14 16:49:17 -07:00
omfs FS/OMFS: block number sanity check during fill_super operation 2014-10-14 02:18:22 +02:00
openpromfs
overlayfs ovl: upper fs should not be R/O 2015-03-18 10:29:48 +01:00
proc /proc/PID/status: show all sets of pid according to ns 2015-04-15 16:35:22 -07:00
pstore pstore: Fix the ramoops module parameters update 2015-03-16 11:14:10 -07:00
qnx4
qnx6
quota Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2015-02-10 15:52:38 -08:00
ramfs fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
reiserfs Merge branch 'iocb' into for-next 2015-04-11 22:24:41 -04:00
romfs fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
squashfs Squashfs: Add LZ4 compression configuration option 2014-11-27 18:48:44 +00:00
sysfs sysfs: Only accept read/write permissions for file attributes 2015-03-25 13:27:57 +01:00
sysv
tracefs tracing: Have mkdir and rmdir be part of tracefs 2015-02-03 12:48:43 -05:00
ubifs fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
udf fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
ufs fs/ufs/super.c: fix potential race condition 2015-02-17 14:34:51 -08:00
xfs Merge branch 'iocb' into for-next 2015-04-11 22:24:41 -04:00
aio.c Merge branch 'for-linus-1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-14 15:31:03 -07:00
anon_inodes.c
attr.c
bad_inode.c don't bother with most of the bad_file_ops methods 2015-02-20 04:03:58 -05:00
binfmt_aout.c assorted conversions to %p[dD] 2014-11-19 13:01:20 -05:00
binfmt_elf_fdpic.c handle suicide on late failure exits in execve() in search_binary_handler() 2014-10-09 02:39:00 -04:00
binfmt_elf.c mm: fold arch_randomize_brk into ARCH_HAS_ELF_RANDOMIZE 2015-04-14 16:49:05 -07:00
binfmt_em86.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
binfmt_flat.c
binfmt_misc.c unfuck binfmt_misc.c (broken by commit e6084d4) 2014-12-17 08:27:14 -05:00
binfmt_script.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
block_dev.c fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
buffer.c page_writeback: clean up mess around cancel_dirty_page() 2015-04-14 16:49:01 -07:00
char_dev.c fs: introduce f_op->mmap_capabilities for nommu mmap support 2015-01-20 14:02:58 -07:00
compat_binfmt_elf.c
compat_ioctl.c Bluetooth: bnep: Add support for get bnep features via ioctl 2015-04-03 23:21:34 +02:00
compat.c vfs: make first argument of dir_context.actor typed 2014-10-31 17:48:54 -04:00
coredump.c coredump: Fix do_coredump() comment 2015-03-06 23:10:29 +01:00
dax.c dax: use pfn_mkwrite to update c/mtime + freeze protection 2015-04-15 16:35:20 -07:00
dcache.c dcache: return -ESTALE not -EBUSY on distributed fs race 2015-04-11 22:24:33 -04:00
dcookies.c
direct-io.c fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
drop_caches.c vmscan: per memory cgroup slab shrinkers 2015-02-12 18:54:09 -08:00
eventfd.c eventfd: don't take the spinlock in eventfd_poll 2015-02-17 14:34:52 -08:00
eventpoll.c epoll: optimize setting task running after blocking 2015-02-13 21:21:40 -08:00
exec.c fs: create proper filename objects using getname_kernel() 2015-01-23 00:22:20 -05:00
fcntl.c vfs: renumber FMODE_NONOTIFY and add to uniqueness check 2015-01-08 15:10:52 -08:00
fhandle.c
file_table.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-10-13 11:28:42 +02:00
file.c fs/file.c: replace get_unused_fd() with get_unused_fd_flags(0) 2014-12-10 17:41:10 -08:00
filesystems.c
fs_pin.c switch the IO-triggering parts of umount to fs_pin 2015-01-25 23:17:29 -05:00
fs_struct.c
fs-writeback.c fs: add dirtytime_expire_seconds sysctl 2015-03-17 12:23:32 -04:00
inode.c Merge branch 'lazytime' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-02-17 16:12:34 -08:00
internal.h trylock_super(): replacement for grab_super_passive() 2015-02-22 11:38:42 -05:00
ioctl.c fsioctl.c: make generic_block_fiemap() signal-tolerant 2015-02-10 14:30:30 -08:00
Kconfig dax: does not work correctly with virtual aliasing caches 2015-02-16 17:56:04 -08:00
Kconfig.binfmt mm: split ET_DYN ASLR from mmap ASLR 2015-04-14 16:49:05 -07:00
libfs.c VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry) 2015-02-22 11:38:41 -05:00
locks.c locks: fix file_lock deletion inside loop 2015-03-27 07:18:20 -04:00
Makefile This adds the new tracefs file system. This has been in linux-next for 2015-04-14 10:22:29 -07:00
mbcache.c
mount.h switch the IO-triggering parts of umount to fs_pin 2015-01-25 23:17:29 -05:00
mpage.c vfs: guard end of device for mpage interface 2014-10-09 22:25:53 -04:00
namei.c remove incorrect comment in lookup_one_len() 2015-04-11 22:24:30 -04:00
namespace.c VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry) 2015-02-22 11:38:41 -05:00
no-block.c
nsfs.c take the targets of /proc/*/ns/* symlinks to separate fs 2014-12-10 21:30:20 -05:00
open.c NFS: fix BUG() crash in notify_change() with patch to chown_common() 2015-04-11 22:24:34 -04:00
pipe.c fs: move struct kiocb to fs.h 2015-03-25 20:28:11 -04:00
pnode.c mnt: Move the clear of MNT_LOCKED from copy_tree to it's callers. 2014-12-02 10:46:50 -06:00
pnode.h
posix_acl.c VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry) 2015-02-22 11:38:41 -05:00
proc_namespace.c vfs: add support for a lazytime mount option 2015-02-05 02:45:00 -05:00
read_write.c switch {compat_,}do_readv_writev() to {compat_,}import_iovec() 2015-04-11 22:27:12 -04:00
readdir.c vfs: make first argument of dir_context.actor typed 2014-10-31 17:48:54 -04:00
select.c all arches, signal: move restart_block to struct task_struct 2015-02-12 18:54:12 -08:00
seq_file.c bitmap, cpumask, nodemask: remove dedicated formatting functions 2015-02-13 21:21:39 -08:00
signalfd.c fs: Convert show_fdinfo functions to void 2014-11-05 14:13:23 -05:00
splice.c dax: unify ext2/4_{dax,}_file_operations 2015-04-15 16:35:20 -07:00
stack.c
stat.c switch security_inode_getattr() to struct path * 2015-04-11 22:24:32 -04:00
statfs.c
super.c cleancache: remove limit on the number of cleancache enabled filesystems 2015-04-14 16:49:03 -07:00
sync.c vfs: add support for a lazytime mount option 2015-02-05 02:45:00 -05:00
timerfd.c fs: Convert show_fdinfo functions to void 2014-11-05 14:13:23 -05:00
utimes.c
xattr.c new helper: audit_file() 2014-11-19 13:01:26 -05:00