Fix possible filp_cachep memory corruption
In commit 31e6b01f4183 ("fs: rcu-walk for path lookup") we started doing
path lookup using RCU, which then falls back to a careful non-RCU lookup
in case of problems (LOOKUP_REVAL). So do_filp_open() has this "re-do
the lookup carefully" looping case.
However, that means that we must not release the open-intent file data
if we are going to loop around and use it once more!
Fix this by moving the release of the open-intent data to the function
that allocates it (do_filp_open() itself) rather than the helper
functions that can get called multiple times (finish_open() and
do_last()). This makes the logic for the lifetime of that field much
more obvious, and avoids the possible double free.
Reported-by: J. R. Okajima <hooanon05@yahoo.co.jp>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: 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 e52389e..5a2c6eb 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -790,6 +790,8 @@
/* Pick up the filp from the open intent */
filp = nd->intent.open.file;
+ nd->intent.open.file = NULL;
+
/* Has the filesystem initialised the file for us? */
if (filp->f_path.dentry == NULL) {
path_get(&nd->path);