ubifs: Check data node size before truncate

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 <keescook@chromium.org>
Cc: Silvio Cesare <silvio.cesare@gmail.com>
Cc: stable@vger.kernel.org
Fixes: 1e51764a3c2ac ("UBIFS: add new flash file system")
Reported-by: Silvio Cesare <silvio.cesare@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 10 insertions, 1 deletions

diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
index 1406765c3ef9..cef0d76d490a 100644
--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -1393,7 +1393,16 @@ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
                 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);