From d01a2c69296cff9bd052b797b2be1055a96cd644 Mon Sep 17 00:00:00 2001
From: Nick Terrell <terrelln@meta.com>
Date: Thu, 25 May 2023 14:35:49 -0700
Subject: [PATCH] Fix UBSAN issue (zero addition to NULL)

Fix UBSAN issue that came up internally.
---
 lib/compress/zstd_compress.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index 521e5e5d681..19446b63ff3 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -5951,7 +5951,7 @@ static size_t ZSTD_compressStream_generic(ZSTD_CStream* zcs,
     if (zcs->appliedParams.inBufferMode == ZSTD_bm_stable) {
         assert(input->pos >= zcs->stableIn_notConsumed);
         input->pos -= zcs->stableIn_notConsumed;
-        ip -= zcs->stableIn_notConsumed;
+        if (ip) ip -= zcs->stableIn_notConsumed;
         zcs->stableIn_notConsumed = 0;
     }
     if (zcs->appliedParams.inBufferMode == ZSTD_bm_buffered) {