VFS: fix a race in lease-breaking during truncate
It is possible that another process could acquire a new file lease right
after break_lease() is called during a truncate, but before lease-granting
is disabled by the subsequent get_write_access(). Merely switching the
order of the break_lease() and get_write_access() calls prevents this race.
Signed-off-by: David M. Richter <richterd@citi.umich.edu>
Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/open.c b/fs/open.c
index e27c205..1d9e5e9 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -256,24 +256,26 @@
if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
goto dput_and_out;
- /*
- * Make sure that there are no leases.
- */
- error = break_lease(inode, FMODE_WRITE);
- if (error)
- goto dput_and_out;
-
error = get_write_access(inode);
if (error)
goto dput_and_out;
+ /*
+ * Make sure that there are no leases. get_write_access() protects
+ * against the truncate racing with a lease-granting setlease().
+ */
+ error = break_lease(inode, FMODE_WRITE);
+ if (error)
+ goto put_write_and_out;
+
error = locks_verify_truncate(inode, NULL, length);
if (!error) {
DQUOT_INIT(inode);
error = do_truncate(nd.dentry, length, 0, NULL);
}
- put_write_access(inode);
+put_write_and_out:
+ put_write_access(inode);
dput_and_out:
path_release(&nd);
out:
