From 953f918d548b569d37467fadb7266d0cd93a9ff6 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 30 Jul 2018 14:27:15 -0700
Subject: [PATCH] squashfs: more metadata hardening

commit d512584780d3e6a7cacb2f482834849453d444a1 upstream.

Anatoly reports another squashfs fuzzing issue, where the decompression
parameters themselves are in a compressed block.

This causes squashfs_read_data() to be called in order to read the
decompression options before the decompression stream having been set
up, making squashfs go sideways.

Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Acked-by: Phillip Lougher <phillip.lougher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/squashfs/block.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
index 2751476e6b6e..f098b9f1c396 100644
--- a/fs/squashfs/block.c
+++ b/fs/squashfs/block.c
@@ -167,6 +167,8 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
 	}
 
 	if (compressed) {
+		if (!msblk->stream)
+			goto read_failure;
 		length = squashfs_decompress(msblk, bh, b, offset, length,
 			output);
 		if (length < 0)
-- 
2.20.1