ext4: atomically set inode->i_flags in ext4_set_inode_flags()
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> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -38,6 +38,7 @@
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#include <linux/slab.h>
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#include <linux/slab.h>
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#include <linux/ratelimit.h>
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#include <linux/ratelimit.h>
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#include <linux/aio.h>
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#include <linux/aio.h>
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#include <linux/bitops.h>
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#include "ext4_jbd2.h"
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#include "ext4_jbd2.h"
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#include "xattr.h"
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#include "xattr.h"
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@ -3921,18 +3922,20 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
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void ext4_set_inode_flags(struct inode *inode)
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void ext4_set_inode_flags(struct inode *inode)
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{
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{
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unsigned int flags = EXT4_I(inode)->i_flags;
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unsigned int flags = EXT4_I(inode)->i_flags;
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unsigned int new_fl = 0;
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inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
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if (flags & EXT4_SYNC_FL)
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if (flags & EXT4_SYNC_FL)
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inode->i_flags |= S_SYNC;
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new_fl |= S_SYNC;
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if (flags & EXT4_APPEND_FL)
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if (flags & EXT4_APPEND_FL)
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inode->i_flags |= S_APPEND;
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new_fl |= S_APPEND;
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if (flags & EXT4_IMMUTABLE_FL)
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if (flags & EXT4_IMMUTABLE_FL)
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inode->i_flags |= S_IMMUTABLE;
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new_fl |= S_IMMUTABLE;
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if (flags & EXT4_NOATIME_FL)
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if (flags & EXT4_NOATIME_FL)
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inode->i_flags |= S_NOATIME;
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new_fl |= S_NOATIME;
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if (flags & EXT4_DIRSYNC_FL)
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if (flags & EXT4_DIRSYNC_FL)
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inode->i_flags |= S_DIRSYNC;
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new_fl |= S_DIRSYNC;
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set_mask_bits(&inode->i_flags,
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S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC, new_fl);
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}
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}
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/* Propagate flags from i_flags to EXT4_I(inode)->i_flags */
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/* Propagate flags from i_flags to EXT4_I(inode)->i_flags */
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@ -196,6 +196,21 @@ static inline unsigned long __ffs64(u64 word)
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#ifdef __KERNEL__
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#ifdef __KERNEL__
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#ifndef set_mask_bits
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#define set_mask_bits(ptr, _mask, _bits) \
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({ \
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const typeof(*ptr) mask = (_mask), bits = (_bits); \
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typeof(*ptr) old, new; \
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\
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do { \
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old = ACCESS_ONCE(*ptr); \
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new = (old & ~mask) | bits; \
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} while (cmpxchg(ptr, old, new) != old); \
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\
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new; \
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})
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#endif
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#ifndef find_last_bit
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#ifndef find_last_bit
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/**
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/**
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* find_last_bit - find the last set bit in a memory region
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* find_last_bit - find the last set bit in a memory region
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