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Use mremap in zend_mm_chunk_extend if available

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As suggested by https://twitter.com/grsecurity. This saves an
mmap+munmap cycle in case the mapping cannot be extended in-place.
This commit is contained in:
Nikita Popov
2019-02-14 17:25:13 +01:00
parent 3ef9f23fce
commit 7d0d94e230
1 changed files with 18 additions and 6 deletions
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24
Zend/zend_alloc.c
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@@ -84,11 +84,6 @@
#include <errno.h>
#ifndef _WIN32
# ifdef HAVE_MREMAP
# ifndef _GNU_SOURCE
# define _GNU_SOURCE
# endif
# endif
# include <sys/mman.h>
# ifndef MAP_ANON
# ifdef MAP_ANONYMOUS
@@ -114,6 +109,12 @@ static size_t _real_page_size = ZEND_MM_PAGE_SIZE;
# define REAL_PAGE_SIZE ZEND_MM_PAGE_SIZE
#endif
/* NetBSD has an mremap() function with a signature that is incompatible with Linux (WTF?),
* so pretend it doesn't exist. */
#ifndef __linux__
# undef HAVE_MREMAP
#endif
#ifndef ZEND_MM_STAT
# define ZEND_MM_STAT 1 /* track current and peak memory usage */
#endif
@@ -410,6 +411,7 @@ stderr_last_error(char *msg)
/* OS Allocation */
/*****************/
#ifndef HAVE_MREMAP
static void *zend_mm_mmap_fixed(void *addr, size_t size)
{
#ifdef _WIN32
@@ -438,6 +440,7 @@ static void *zend_mm_mmap_fixed(void *addr, size_t size)
return ptr;
#endif
}
#endif
static void *zend_mm_mmap(size_t size)
{
@@ -797,7 +800,16 @@ static int zend_mm_chunk_extend(zend_mm_heap *heap, void *addr, size_t old_size,
}
}
#endif
#ifndef _WIN32
#ifdef HAVE_MREMAP
/* We don't use MREMAP_MAYMOVE due to alignment requirements. */
void *ptr = mremap(addr, old_size, new_size, 0);
if (ptr == MAP_FAILED) {
return 0;
}
/* Sanity check: The mapping shouldn't have moved. */
ZEND_ASSERT(ptr == addr);
return 1;
#elif !defined(_WIN32)
return (zend_mm_mmap_fixed((char*)addr + old_size, new_size - old_size) != NULL);
#else
return 0;