From 6724aa4ce1d5362e67c166eb68a013cf3d0b3c41 Mon Sep 17 00:00:00 2001
From: Maks Mishin <maks.mishinFZ@gmail.com>
Date: Thu, 29 Feb 2024 23:29:54 +0300
Subject: [PATCH] gzlib: Add check for res of LSEEK

Return value of function LSEEK (lseek64) is not checked, but it is
usually checked for this function.

Found by RASU JSC.
---
 gzlib.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gzlib.c b/gzlib.c
index e485a27..7e2cb18 100644
--- a/gzlib.c
+++ b/gzlib.c
@@ -244,7 +244,8 @@ local gzFile gz_open(const void *path, int fd, const char *mode) {
         return NULL;
     }
     if (state->mode == GZ_APPEND) {
-        LSEEK(state->fd, 0, SEEK_END);  /* so gzoffset() is correct */
+        if (LSEEK(state->fd, 0, SEEK_END) == -1)  /* so gzoffset() is correct */
+            return NULL;
         state->mode = GZ_WRITE;         /* simplify later checks */
     }