diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2014-03-30 10:20:01 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-04-03 12:01:04 -0700 |
| commit | 0a0ae7b3fb0fb301da83f7c7da38807c76b2b869 (patch) | |
| tree | 52faa63e298c6002a1dad381817389ea1f347518 | |
| parent | a2e124daef622d8745510ab24b023027dcdc9146 (diff) | |
| download | lwn-0a0ae7b3fb0fb301da83f7c7da38807c76b2b869.tar.gz lwn-0a0ae7b3fb0fb301da83f7c7da38807c76b2b869.zip | |
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>
| -rw-r--r-- | fs/ext4/inode.c | 15 | ||||
| -rw-r--r-- | include/linux/bitops.h | 15 |
2 files changed, 24 insertions, 6 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 21dff8f236f6..f9e11df768d5 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -38,6 +38,7 @@ #include <linux/slab.h> #include <linux/ratelimit.h> #include <linux/aio.h> +#include <linux/bitops.h> #include "ext4_jbd2.h" #include "xattr.h" @@ -4044,18 +4045,20 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc) void ext4_set_inode_flags(struct inode *inode) { unsigned int flags = EXT4_I(inode)->i_flags; + unsigned int new_fl = 0; - inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC); if (flags & EXT4_SYNC_FL) - inode->i_flags |= S_SYNC; + new_fl |= S_SYNC; if (flags & EXT4_APPEND_FL) - inode->i_flags |= S_APPEND; + new_fl |= S_APPEND; if (flags & EXT4_IMMUTABLE_FL) - inode->i_flags |= S_IMMUTABLE; + new_fl |= S_IMMUTABLE; if (flags & EXT4_NOATIME_FL) - inode->i_flags |= S_NOATIME; + new_fl |= S_NOATIME; if (flags & EXT4_DIRSYNC_FL) - inode->i_flags |= S_DIRSYNC; + new_fl |= S_DIRSYNC; + set_mask_bits(&inode->i_flags, + S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC, new_fl); } /* Propagate flags from i_flags to EXT4_I(inode)->i_flags */ diff --git a/include/linux/bitops.h b/include/linux/bitops.h index a3b6b82108b9..c1dde8e00d25 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -185,6 +185,21 @@ static inline unsigned long __ffs64(u64 word) #ifdef __KERNEL__ +#ifndef set_mask_bits +#define set_mask_bits(ptr, _mask, _bits) \ +({ \ + const typeof(*ptr) mask = (_mask), bits = (_bits); \ + typeof(*ptr) old, new; \ + \ + do { \ + old = ACCESS_ONCE(*ptr); \ + new = (old & ~mask) | bits; \ + } while (cmpxchg(ptr, old, new) != old); \ + \ + new; \ +}) +#endif + #ifndef find_last_bit /** * find_last_bit - find the last set bit in a memory region |