Unverified Commit 62a86985 authored Feb 26, 2020 by Gao Xiang Committed by Michael Bestas Apr 16, 2024

erofs: use LZ4_decompress_safe() for full decoding

As Lasse pointed out, "EROFS uses LZ4_decompress_safe_partial
for both partial and full blocks. Thus when it is decoding a
full block, it doesn't know if the LZ4 decoder actually decoded
all the input. The real uncompressed size could be bigger than
the value stored in the file system metadata.

Using LZ4_decompress_safe instead of _safe_partial when
decompressing a full block would help to detect errors."

So it's reasonable to use _safe in case of potential corrupted
images and it might have some speed gain as well although
I didn't observe much difference.

Note that legacy compressor (< 5.3, no LZ4_0PADDING) could
encode extra data in a pcluster, which is excluded as well.

Cc: Lasse Collin <lasse.collin@tukaani.org>
Fixes: 0ffd71bc ("staging: erofs: introduce LZ4 decompression inplace")
[ Gao Xiang: v5.3+, I will manually backport this to stable later. ]
Link: https://lore.kernel.org/r/20200226081008.86348-2-gaoxiang25@huawei.com


Reviewed-by: Chao Yu <yuchao0@huawei.com>
Change-Id: Ic8f01ed11c94983fdd1c5b6252b8d15bc8d70c3f
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>

parent 69ddc631

fs/erofs/decompressor.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -161,9 +161,15 @@ static int z_erofs_lz4_decompress(struct z_erofs_decompress_req rq, u8 out)
		}
		}

		/* legacy format could compress extra data in a pcluster. */
		if (rq->partial_decoding \|\| !support_0padding)
		ret = LZ4_decompress_safe_partial(src + inputmargin, out,
		inlen, rq->outputsize,
		rq->outputsize);
		else
		ret = LZ4_decompress_safe(src + inputmargin, out,
		inlen, rq->outputsize);

		if (ret < 0) {
		erofs_err(rq->sb, "failed to decompress, in[%u, %u] out[%u]",
		inlen, inputmargin, rq->outputsize);