ext4: atomically set inode->i_flags in ext4_set_inode_flags()
authorTheodore Ts'o <tytso@mit.edu>
Sun, 30 Mar 2014 14:20:01 +0000 (10:20 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 3 Apr 2014 19:01:04 +0000 (12:01 -0700)
commit0a0ae7b3fb0fb301da83f7c7da38807c76b2b869
tree52faa63e298c6002a1dad381817389ea1f347518
parenta2e124daef622d8745510ab24b023027dcdc9146
ext4: atomically set inode->i_flags in ext4_set_inode_flags()

commit 00a1a053ebe5febcfc2ec498bd894f035ad2aa06 upstream.

Use cmpxchg() to atomically set i_flags instead of clearing out the
S_IMMUTABLE, S_APPEND, etc. flags and then setting them from the
EXT4_IMMUTABLE_FL, EXT4_APPEND_FL flags, since this opens up a race
where an immutable file has the immutable flag cleared for a brief
window of time.

Reported-by: John Sullivan <jsrhbz@kanargh.force9.co.uk>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/ext4/inode.c
include/linux/bitops.h