[PATCH v2 2/2] erofs-utils: lib: return error on ZSTD decompression length mismatch

[Utkal Singh <singhutkal015@gmail.com>]

When ZSTD_decompress() succeeds but produces a different number of
bytes than expected, the code logs an error and jumps to cleanup.
However, it does not set ret to an error code. Since ret still
holds the positive ZSTD output size, the caller treats it as
success via the 'if (ret < 0)' check in z_erofs_read_one_data(),
causing silently corrupted data to be returned.

Set ret to -EIO before jumping to cleanup, consistent with the
ZSTD_isError() error handling path above.

Signed-off-by: Utkal Singh <singhutkal015@gmail.com>
---
 lib/decompress.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/decompress.c b/lib/decompress.c
index fb81039..a27881c 100644
--- a/lib/decompress.c
+++ b/lib/decompress.c
@@ -75,6 +75,7 @@ static int z_erofs_decompress_zstd(struct z_erofs_decompress_req *rq)
 	if (ret != (int)total) {
 		erofs_err("ZSTD decompress length mismatch %d, expected %d",
 			  ret, total);
+		ret = -EIO;
 		goto out;
 	}
 	if (rq->decodedskip || total != rq->decodedlength)
-- 
2.43.0