[PATCH 4.14 72/89] ubifs: Check data node size before truncate

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Richard Weinberger <rich...@nod.at>

commit 95a22d2084d72ea067d8323cc85677dba5d97cae upstream.

Check whether the size is within bounds before using it.
If the size is not correct, abort and dump the bad data node.

Cc: Kees Cook <keesc...@chromium.org>
Cc: Silvio Cesare <silvio.ces...@gmail.com>
Cc: sta...@vger.kernel.org
Fixes: 1e51764a3c2ac ("UBIFS: add new flash file system")
Reported-by: Silvio Cesare <silvio.ces...@gmail.com>
Signed-off-by: Richard Weinberger <rich...@nod.at>
Reviewed-by: Kees Cook <keesc...@chromium.org>
Signed-off-by: Richard Weinberger <rich...@nod.at>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 fs/ubifs/journal.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -1388,7 +1388,16 @@ int ubifs_jnl_truncate(struct ubifs_info
                else if (err)
                        goto out_free;
                else {
-                       if (le32_to_cpu(dn->size) <= dlen)
+                       int dn_len = le32_to_cpu(dn->size);
+
+                       if (dn_len <= 0 || dn_len > UBIFS_BLOCK_SIZE) {
+                               ubifs_err(c, "bad data node (block %u, inode 
%lu)",
+                                         blk, inode->i_ino);
+                               ubifs_dump_node(c, dn);
+                               goto out_free;
+                       }
+
+                       if (dn_len <= dlen)
                                dlen = 0; /* Nothing to do */
                        else {
                                err = truncate_data_node(c, inode, blk, dn, 
&dlen);