[SECURITY PATCH 076/117] fs/jfs: Do not move to leaf level if name length is negative

[Daniel Kiper]

From: Daniel Axtens <dja@axtens.net>

Fuzzing JFS revealed crashes where a negative number would be passed
to le_to_cpu16_copy(). There it would be cast to a large positive number
and the copy would read and write off the end of the respective buffers.

Catch this at the top as well as the bottom of the loop.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/jfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/grub-core/fs/jfs.c b/grub-core/fs/jfs.c
index d5a6d6527..e5bbda61c 100644
--- a/grub-core/fs/jfs.c
+++ b/grub-core/fs/jfs.c
@@ -567,7 +567,7 @@ grub_jfs_getent (struct grub_jfs_diropen *diro)
 
   /* Move down to the leaf level.  */
   nextent = leaf->next;
-  if (leaf->next != 255)
+  if (leaf->next != 255 && len > 0)
     do
       {
        next_leaf = &diro->next_leaf[nextent];
-- 
2.11.0