[PATCH 01/10] locks: close potential race in lease_get_mtime
From: Jeff Layton <hidden>
Date: 2014-08-23 14:41:09
Also in:
linux-fsdevel, linux-nfs
Subsystem:
file locking (flock() and fcntl()/lockf()), filesystems (vfs and infrastructure), the rest · Maintainers:
Jeff Layton, Chuck Lever, Alexander Viro, Christian Brauner, Linus Torvalds
Possibly related (same subject, not in this thread)
- 2014-08-24 · Re: [PATCH 01/10] locks: close potential race in lease_get_mtime · Christoph Hellwig <hidden>
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 <redacted> Signed-off-by: Jeff Layton <jlayton-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org> --- fs/locks.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index d7e15a256f8f..58ce8897f2e4 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;
--
1.9.3