fs, xattr: fix bug when removing a name not in xattr list

Commit 38f38657444d ("xattr: extract simple_xattr code from tmpfs") moved
some code from tmpfs but introduced a subtle bug along the way.

If the name passed to simple_xattr_remove() does not exist in the list of
xattrs, then it is possible to call kfree(new_xattr) when new_xattr is
actually initialized to itself on the stack via uninitialized_var().

This causes a BUG() since the memory was not allocated via the slab
allocator and was not bypassed through to the page allocator because it
was too large.

Initialize the local variable to NULL so the kfree() never takes place.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/xattr.c b/fs/xattr.c
index e164dddb8e9660dc1de0cfb1d6a6abd3da13ed6b..e21c119f4f99d8512208a9c08983dd5f9c25d821 100644 (file)
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -846,7 +846,7 @@ static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
                              const void *value, size_t size, int flags)
 {
        struct simple_xattr *xattr;
-       struct simple_xattr *uninitialized_var(new_xattr);
+       struct simple_xattr *new_xattr = NULL;
        int err = 0;
 
        /* value == NULL means remove */