From b80770e99e1d89c0bef4b6c80263fed5f2c0f413 Mon Sep 17 00:00:00 2001 From: Gao Xiang Date: Wed, 26 Feb 2020 16:10:07 +0800 Subject: [PATCH] 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 Fixes: 83518bdf1d75 ("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 Signed-off-by: Gao Xiang --- fs/erofs/decompressor.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c index 5779a15c2cd6f..cd978af6bdb9c 100644 --- a/fs/erofs/decompressor.c +++ b/fs/erofs/decompressor.c @@ -157,9 +157,15 @@ static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out) } } - ret = LZ4_decompress_safe_partial(src + inputmargin, out, - inlen, rq->outputsize, - rq->outputsize); + /* 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); -- 2.39.5