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erofs: avoid infinite loop due to incomplete zstd-compressed data

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Currently, the decompression logic incorrectly spins if compressed
data is truncated in crafted (deliberately corrupted) images.

Fixes: 7c35de4df1 ("erofs: Zstandard compression support")
Reported-by: Robert Morris <rtm@csail.mit.edu>
Closes: https://lore.kernel.org/r/50958.1761605413@localhost
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chunhai Guo <guochunhai@vivo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
This commit is contained in:
Gao Xiang 2025-10-31 13:47:39 +08:00
parent 083d7af335
commit f2a12cc3b9
1 changed files with 7 additions and 4 deletions
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11
fs/erofs/decompressor_zstd.c
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@ -172,7 +172,6 @@ static int z_erofs_zstd_decompress(struct z_erofs_decompress_req *rq,
dctx.bounce = strm->bounce;
do {
dctx.avail_out = out_buf.size - out_buf.pos;
dctx.inbuf_sz = in_buf.size;
dctx.inbuf_pos = in_buf.pos;
err = z_erofs_stream_switch_bufs(&dctx, &out_buf.dst,
@ -188,14 +187,18 @@ static int z_erofs_zstd_decompress(struct z_erofs_decompress_req *rq,
in_buf.pos = dctx.inbuf_pos;
zerr = zstd_decompress_stream(stream, &out_buf, &in_buf);
if (zstd_is_error(zerr) || (!zerr && rq->outputsize)) {
dctx.avail_out = out_buf.size - out_buf.pos;
if (zstd_is_error(zerr) ||
((rq->outputsize + dctx.avail_out) && (!zerr || (zerr > 0 &&
!(rq->inputsize + in_buf.size - in_buf.pos))))) {
erofs_err(sb, "failed to decompress in[%u] out[%u]: %s",
rq->inputsize, rq->outputsize,
zerr ? zstd_get_error_name(zerr) : "unexpected end of stream");
zstd_is_error(zerr) ? zstd_get_error_name(zerr) :
"unexpected end of stream");
err = -EFSCORRUPTED;
break;
}
} while (rq->outputsize || out_buf.pos < out_buf.size);
} while (rq->outputsize + dctx.avail_out);
if (dctx.kout)
kunmap_local(dctx.kout);