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From a714d2561b78985ec85f3056aac83c603cbaaa5f Mon Sep 17 00:00:00 2001
From: wang_yue111 <648774160@qq.com>
Date: Wed, 7 Apr 2021 10:00:53 +0800
Subject: [PATCH] Fix wrong zmalloc_size() assumption. (#7963)
When using a system with no malloc_usable_size(), zmalloc_size() assumed
that the heap allocator always returns blocks that are long-padded.
This may not always be the case, and will result with zmalloc_size()
returning a size that is bigger than allocated. At least in one case
this leads to out of bound write, process crash and a potential security
vulnerability.
Effectively this does not affect the vast majority of users, who use
jemalloc or glibc.
This problem along with a (different) fix was reported by Drew DeVault.
---
src/zmalloc.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/src/zmalloc.c b/src/zmalloc.c
index cc47f71..67b1b65 100644
--- a/src/zmalloc.c
+++ b/src/zmalloc.c
@@ -186,9 +186,6 @@ void *zrealloc(void *ptr, size_t size) {
size_t zmalloc_size(void *ptr) {
void *realptr = (char*)ptr-PREFIX_SIZE;
size_t size = *((size_t*)realptr);
- /* Assume at least that all the allocations are padded at sizeof(long) by
- * the underlying allocator. */
- if (size&(sizeof(long)-1)) size += sizeof(long)-(size&(sizeof(long)-1));
return size+PREFIX_SIZE;
}
#endif
--
2.23.0
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