From b8ccf8e46bab6ee9d63a6e392c3b33b9aa89255c Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Fri, 7 Dec 2012 22:33:11 -0500 Subject: [PATCH] page-align initial brk value used by malloc in shared libc this change fixes an obscure issue with some nonstandard kernels, where the initial brk syscall returns a pointer just past the end of bss rather than the beginning of a new page. in that case, the dynamic linker has already reclaimed the space between the end of bss and the page end for use by malloc, and memory corruption (allocating the same memory twice) will occur when malloc again claims it on the first call to brk. --- src/malloc/malloc.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c index 88a31ae4..1a6d1493 100644 --- a/src/malloc/malloc.c +++ b/src/malloc/malloc.c @@ -196,7 +196,11 @@ static int init_malloc(size_t n) return 0; } - mal.brk = __brk(0) + 2*SIZE_ALIGN-1 & -SIZE_ALIGN; + mal.brk = __brk(0); +#ifdef SHARED + mal.brk = mal.brk + PAGE_SIZE-1 & -PAGE_SIZE; +#endif + mal.brk = mal.brk + 2*SIZE_ALIGN-1 & -SIZE_ALIGN; c = expand_heap(n); -- 2.20.1