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 <[email protected]> Signed-off-by: Gao Xiang <[email protected]> --- 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 c77cec4327fa..be8d9adef236 100644 --- a/fs/erofs/decompressor.c +++ b/fs/erofs/decompressor.c @@ -165,14 +165,18 @@ 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; } -- 2.17.1
