From 05b8e7341ea958738b441bd8384c325f2ddc740c Mon Sep 17 00:00:00 2001 From: Gao Xiang Date: Wed, 26 Feb 2020 16:10:08 +0800 Subject: [PATCH] erofs: handle corrupted images whose decompressed size less than it'd be As Lasse pointed out, "Looking at fs/erofs/decompress.c, the return value from LZ4_decompress_safe_partial is only checked for negative value to catch errors. ... So if I understood it correctly, if there is bad data whose uncompressed size is much less than it should be, it can leave part of the output buffer untouched and expose the previous data as the file content. " Let's fix it now. Cc: Lasse Collin Fixes: d6c90688e3d0 ("staging: erofs: introduce generic decompression backend") [ Gao Xiang: v5.3+, I will manually backport this to stable later. ] Link: https://lore.kernel.org/r/20200226081008.86348-3-gaoxiang25@huawei.com Reviewed-by: Chao Yu Signed-off-by: Gao Xiang --- fs/erofs/decompressor.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c index cd978af6bdb9c..5d2d819406794 100644 --- a/fs/erofs/decompressor.c +++ b/fs/erofs/decompressor.c @@ -166,14 +166,18 @@ static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out) 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); + if (ret != rq->outputsize) { + erofs_err(rq->sb, "failed to decompress %d in[%u, %u] out[%u]", + ret, inlen, inputmargin, rq->outputsize); + WARN_ON(1); print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET, 16, 1, src + inputmargin, inlen, true); print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET, 16, 1, out, rq->outputsize, true); + + if (ret >= 0) + memset(out + ret, 0, rq->outputsize - ret); ret = -EIO; } -- 2.39.5