Commit eafc0a02 authored by Guo Xuenan's avatar Guo Xuenan Committed by Linus Torvalds

lz4: fix LZ4_decompress_safe_partial read out of bound

When partialDecoding, it is EOF if we've either filled the output buffer
or can't proceed with reading an offset for following match.

In some extreme corner cases when compressed data is suitably corrupted,
UAF will occur.  As reported by KASAN [1], LZ4_decompress_safe_partial
may lead to read out of bound problem during decoding.  lz4 upstream has
fixed it [2] and this issue has been disscussed here [3] before.

current decompression routine was ported from lz4 v1.8.3, bumping
lib/lz4 to v1.9.+ is certainly a huge work to be done later, so, we'd
better fix it first.

[1] https://lore.kernel.org/all/000000000000830d1205cf7f0477@google.com/
[2] https://github.com/lz4/lz4/commit/c5d6f8a8be3927c0bec91bcc58667a6cfad244ad#
[3] https://lore.kernel.org/all/CC666AE8-4CA4-4951-B6FB-A2EFDE3AC03B@fb.com/

Link: https://lkml.kernel.org/r/20211111105048.2006070-1-guoxuenan@huawei.com
Reported-by: syzbot+63d688f1d899c588fb71@syzkaller.appspotmail.com
Signed-off-by: default avatarGuo Xuenan <guoxuenan@huawei.com>
Reviewed-by: default avatarNick Terrell <terrelln@fb.com>
Acked-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
Cc: Yann Collet <cyan@fb.com>
Cc: Chengyang Fan <cy.fan@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 66f133ce
......@@ -271,8 +271,12 @@ static FORCE_INLINE int LZ4_decompress_generic(
ip += length;
op += length;
/* Necessarily EOF, due to parsing restrictions */
if (!partialDecoding || (cpy == oend))
/* Necessarily EOF when !partialDecoding.
* When partialDecoding, it is EOF if we've either
* filled the output buffer or
* can't proceed with reading an offset for following match.
*/
if (!partialDecoding || (cpy == oend) || (ip >= (iend - 2)))
break;
} else {
/* may overwrite up to WILDCOPYLENGTH beyond cpy */
......
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