From 095820016689dfdc9141f477a86de22054c86078 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 23 Mar 2011 13:24:00 -0400 Subject: [PATCH] very cheap double-free checks in malloc --- src/malloc/malloc.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c index 3c08c41e..a4eefda9 100644 --- a/src/malloc/malloc.c +++ b/src/malloc/malloc.c @@ -393,6 +393,8 @@ void *realloc(void *p, size_t n) char *base = (char *)self - extra; size_t oldlen = n0 + extra; size_t newlen = n + extra; + /* Crash on realloc of freed chunk */ + if ((uintptr_t)base < mal.brk) *(char *)0=0; if (newlen < PAGE_SIZE && (new = malloc(n))) { memcpy(new, p, n-OVERHEAD); free(p); @@ -454,6 +456,8 @@ void free(void *p) size_t extra = self->data[-1]; char *base = (char *)self - extra; size_t len = CHUNK_SIZE(self) + extra; + /* Crash on double free */ + if ((uintptr_t)base < mal.brk) *(char *)0=0; __munmap(base, len); return; } -- 2.25.1