From: Olaf Kirch <okir@suse.de>

[PATCH] Fix miscompare in __posix_lock_file

 If an application requests the same lock twice, the
 kernel should just leave the existing lock in place.
 Currently, it will install a second lock of the same type.

 Signed-off-by: Olaf Kirch <okir@suse.de>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/locks.c b/fs/locks.c
index f7daa5f48949..7eb1d77b9204 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -829,12 +829,16 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request)
                 /* Detect adjacent or overlapping regions (if same lock type)
                  */
                 if (request->fl_type == fl->fl_type) {
+                        /* In all comparisons of start vs end, use
+                         * "start - 1" rather than "end + 1". If end
+                         * is OFFSET_MAX, end + 1 will become negative.
+                         */
                         if (fl->fl_end < request->fl_start - 1)
                                 goto next_lock;
                         /* If the next lock in the list has entirely bigger
                          * addresses than the new one, insert the lock here.
                          */
-                        if (fl->fl_start > request->fl_end + 1)
+                        if (fl->fl_start - 1 > request->fl_end)
                                 break;
 
                         /* If we come here, the new and old lock are of the