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Cramfs: fix abad comparison when wrap-arounds occur 

commit 672ca9dd13 upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicolas Pitre 2018-10-30 13:26:15 -04:00 committed by Greg Kroah-Hartman
parent 245af7ee61
commit aa52629c60
1 changed files with 2 additions and 1 deletions
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3
fs/cramfs/inode.c
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@ -186,7 +186,8 @@ static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned i
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;
}