linux-kernel - [PATCH 3.16 140/328] ubifs: Check data node size before truncate

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Message-ID: <lsq.1544392233.170628969@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Kees Cook" <keescook@...omium.org>,
        "Silvio Cesare" <silvio.cesare@...il.com>,
        "Richard Weinberger" <richard@....at>
Subject: [PATCH 3.16 140/328] ubifs: Check data node size before truncate

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Richard Weinberger <richard@....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 <keescook@...omium.org>
Cc: Silvio Cesare <silvio.cesare@...il.com>
Fixes: 1e51764a3c2ac ("UBIFS: add new flash file system")
Reported-by: Silvio Cesare <silvio.cesare@...il.com>
Signed-off-by: Richard Weinberger <richard@....at>
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Richard Weinberger <richard@....at>
[bwh: Backported to 3.16: Drop first argument to ubifs_err()]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/ubifs/journal.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -1186,7 +1186,16 @@ 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("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 {
 				int compr_type = le16_to_cpu(dn->compr_type);