[SECURITY PATCH 078/117] fs/jfs: Catch infinite recursion

[Daniel Kiper]

From: Daniel Axtens <dja@axtens.net>

It's possible with a fuzzed filesystem for JFS to keep getblk()-ing
the same data over and over again, leading to stack exhaustion.

Check if we'd be calling the function with exactly the same data as
was passed in, and if so abort.

I'm not sure what the performance impact of this is and am open to
better ideas.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/jfs.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/grub-core/fs/jfs.c b/grub-core/fs/jfs.c
index 804c42d31..6f7c43904 100644
--- a/grub-core/fs/jfs.c
+++ b/grub-core/fs/jfs.c
@@ -304,7 +304,16 @@ getblk (struct grub_jfs_treehead *treehead,
                           << (grub_le_to_cpu16 (data->sblock.log2_blksz)
                               - GRUB_DISK_SECTOR_BITS), 0,
                           sizeof (*tree), (char *) tree))
-       ret = getblk (&tree->treehead, &tree->extents[0], 254, data, blk);
+       {
+         if (grub_memcmp (&tree->treehead, treehead, sizeof (struct 
grub_jfs_treehead)) ||
+             grub_memcmp (&tree->extents, extents, 254 * sizeof (struct 
grub_jfs_tree_extent)))
+           ret = getblk (&tree->treehead, &tree->extents[0], 254, data, blk);
+         else
+           {
+             grub_error (GRUB_ERR_BAD_FS, "jfs: infinite recursion detected");
+             ret = -1;
+           }
+       }
       grub_free (tree);
       return ret;
     }
-- 
2.11.0