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erofs: use LZ4_decompress_safe() for full decoding

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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: 0ffd71bcc3 ("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>
This commit is contained in:
Gao Xiang 2020-02-26 16:10:07 +08:00 committed by Michael Bestas
parent 69ddc63110
commit 62a86985df
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GPG Key ID: CC95044519BE6669
1 changed files with 9 additions and 3 deletions
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6
fs/erofs/decompressor.c
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@ -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);