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Re: [PATCH v2 5/7] malloc: Verify the integrity of mmapped chunks in calloc.
- From: Florian Weimer <fweimer at redhat dot com>
- To: Istvan Kurucsai <pistukem at gmail dot com>
- Cc: libc-alpha at sourceware dot org, DJ Delorie <dj at redhat dot com>
- Date: Fri, 17 Aug 2018 16:14:57 +0200
- Subject: Re: [PATCH v2 5/7] malloc: Verify the integrity of mmapped chunks in calloc.
- References: <1510068430-27816-1-git-send-email-pistukem@gmail.com> <1510068430-27816-6-git-send-email-pistukem@gmail.com>
On 11/07/2017 04:27 PM, Istvan Kurucsai wrote:
* malloc/malloc.c (__libc_calloc): Check mmapped chunks.
---
malloc/malloc.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 8e48952..5eb661e 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3447,6 +3447,15 @@ __libc_calloc (size_t n, size_t elem_size)
/* Two optional cases in which clearing not necessary */
if (chunk_is_mmapped (p))
{
+ size_t pagesize = GLRO (dl_pagesize);
+ INTERNAL_SIZE_T offset = prev_size (p);
+ INTERNAL_SIZE_T size = chunksize (p);
+ uintptr_t block = (uintptr_t) p - offset;
+ size_t total_size = offset + size;
+ if (__glibc_unlikely ((block | total_size) & (pagesize - 1)) != 0
+ || __glibc_unlikely (!powerof2 ((uintptr_t) mem & (pagesize - 1))))
+ malloc_printerr ("calloc(): invalid mmapped chunk");
+
if (__builtin_expect (perturb_byte, 0))
return memset (mem, 0, sz);
Sorry, I don't understand the powerof2 check. Could you elaborate?
Thanks,
Florian