From 927d67855e2e83b6b06eb9095f65e4e695d6af7e Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 30 Jul 2024 16:21:39 -0700
Subject: [PATCH] Cleaner overflow checking in xheader_read

* src/xheader.c (xheader_read): Prefer ckd_add to
doing overflow checking by hand.
---
 src/xheader.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/xheader.c b/src/xheader.c
index e2b124b8..96762c34 100644
--- a/src/xheader.c
+++ b/src/xheader.c
@@ -783,12 +783,13 @@ xheader_read (struct xheader *xhdr, union block *p, off_t size)
   if (size < 0)
     size = 0; /* Already diagnosed.  */
 
-  if (SIZE_MAX - BLOCKSIZE <= size)
+  size_t size_plus_1;
+  if (ckd_add (&size_plus_1, size, BLOCKSIZE + 1))
     xalloc_die ();
+  size = size_plus_1 - 1;
 
-  size += BLOCKSIZE;
   xhdr->size = size;
-  xhdr->buffer = xmalloc (size + 1);
+  xhdr->buffer = xmalloc (size_plus_1);
   xhdr->buffer[size] = '\0';
 
   do