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authorJeff Layton <jlayton@primarydata.com>2014-08-22 10:18:44 -0400
committerJeff Layton <jlayton@primarydata.com>2014-10-07 14:06:12 -0400
commitbfe8602436c803c6d5e271d52cd985d491a7470a (patch)
tree17b28bd50fd22ae65f90e9bd09cc5b14415a0049 /fs/locks.c
parente0b93eddfe17dcb7d644eb5d6ad02a86fc41a977 (diff)
downloadlwn-bfe8602436c803c6d5e271d52cd985d491a7470a.tar.gz
lwn-bfe8602436c803c6d5e271d52cd985d491a7470a.zip
locks: close potential race in lease_get_mtime
lease_get_mtime is called without the i_lock held, so there's no guarantee about the stability of the list. Between the time when we assign "flock" and then dereference it to check whether it's a lease and for write, the lease could be freed. Ensure that that doesn't occur by taking the i_lock before trying to check the lease. Cc: J. Bruce Fields <bfields@fieldses.org> Signed-off-by: Jeff Layton <jlayton@primarydata.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'fs/locks.c')
-rw-r--r--fs/locks.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/fs/locks.c b/fs/locks.c
index f5f648e003dd..def1ac2e87bd 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1456,8 +1456,18 @@ EXPORT_SYMBOL(__break_lease);
*/
void lease_get_mtime(struct inode *inode, struct timespec *time)
{
- struct file_lock *flock = inode->i_flock;
- if (flock && IS_LEASE(flock) && (flock->fl_type == F_WRLCK))
+ bool has_lease = false;
+ struct file_lock *flock;
+
+ if (inode->i_flock) {
+ spin_lock(&inode->i_lock);
+ flock = inode->i_flock;
+ if (flock && IS_LEASE(flock) && (flock->fl_type == F_WRLCK))
+ has_lease = true;
+ spin_unlock(&inode->i_lock);
+ }
+
+ if (has_lease)
*time = current_fs_time(inode->i_sb);
else
*time = inode->i_mtime;