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
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6082956..5d1f6fa 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2556,6 +2556,9 @@
void inode_dio_wait(struct inode *inode);
void inode_dio_done(struct inode *inode);
+extern void inode_set_flags(struct inode *inode, unsigned int flags,
+ unsigned int mask);
+
extern const struct file_operations generic_ro_fops;
#define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))