From 086eed9d97b860b2c3484038d225a16e406c757d Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Wed, 28 Sep 2016 10:15:34 +0200
Subject: [PATCH] aprintf: detect wrap-around when growing allocation

On 32bit systems we could otherwise wrap around after 2GB and allocate 0
bytes and crash.

CVE-2016-8618

Bug: https://curl.haxx.se/docs/adv_20161102D.html
Reported-by: Cure53

Upstream-commit: 8732ec40db652c53fa58cd13e2acb8eab6e40874
Signed-off-by: Kamil Dudka <kdudka@redhat.com>
---
 lib/mprintf.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/mprintf.c b/lib/mprintf.c
index b6d9a9c..e47c10a 100644
--- a/lib/mprintf.c
+++ b/lib/mprintf.c
@@ -1011,16 +1011,19 @@ static int alloc_addbyter(int output, FILE *data)
     infop->len =0;
   }
   else if(infop->len+1 >= infop->alloc) {
-    char *newptr;
+    char *newptr = NULL;
+    size_t newsize = infop->alloc*2;
 
-    newptr = realloc(infop->buffer, infop->alloc*2);
+    /* detect wrap-around or other overflow problems */
+    if(newsize > infop->alloc)
+      newptr = realloc(infop->buffer, newsize);
 
     if(!newptr) {
       infop->fail = 1;
       return -1; /* fail */
     }
     infop->buffer = newptr;
-    infop->alloc *= 2;
+    infop->alloc = newsize;
   }
 
   infop->buffer[ infop->len ] = outc;
-- 
2.7.4