Cramfs: fix abad comparison when wrap-arounds occur
authorNicolas Pitre <nicolas.pitre@linaro.org>
Tue, 30 Oct 2018 17:26:15 +0000 (13:26 -0400)
committerNicolas Pitre <nicolas.pitre@linaro.org>
Tue, 30 Oct 2018 18:24:19 +0000 (14:24 -0400)
It is possible for corrupted filesystem images to produce very large
block offsets that may wrap when a length is added, and wrongly pass
the buffer size test.

Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Cc: stable@vger.kernel.org
fs/cramfs/inode.c

index f408994fc632129dcbdceca43cedf2fd14705205..6e000392e4a4172da4eb3550edd01158e5979116 100644 (file)
@@ -202,7 +202,8 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
                        continue;
                blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT;
                blk_offset += offset;
-               if (blk_offset + len > BUFFER_SIZE)
+               if (blk_offset > BUFFER_SIZE ||
+                   blk_offset + len > BUFFER_SIZE)
                        continue;
                return read_buffers[i] + blk_offset;
        }