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a95636682d
Till now pool-os used to contain a mapping from pool_{alloc,free}_area()
to pool_{alloc,free}_area_uaf() in case of DEBUG_UAF, or the regular
malloc-based function. And the *_uaf() functions were in pool.c. But
since 2.4 with the first cleanup of the pools, there has been no more
calls to pool_{alloc,free}_area() from anywhere but pool.c, from exactly
one place each. As such, there's no more need to keep *_uaf() apart in
pool.c, we can inline it into pool-os.h and leave all the OS stuff there,
with pool.c calling either based on DEBUG_UAF. This is cleaner with less
round trips between both files and easier to find.
110 lines
3.5 KiB
C
110 lines
3.5 KiB
C
/*
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* include/haproxy/pool-os.h
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* OS-level interface for memory management
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*
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* Copyright (C) 2000-2020 Willy Tarreau - w@1wt.eu
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation, version 2.1
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* exclusively.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _HAPROXY_POOL_OS_H
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#define _HAPROXY_POOL_OS_H
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#include <sys/mman.h>
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#include <stdlib.h>
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#include <haproxy/api.h>
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/************* normal allocator *************/
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/* allocates an area of size <size> and returns it. The semantics are similar
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* to those of malloc().
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*/
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static forceinline void *pool_alloc_area(size_t size)
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{
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return malloc(size);
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}
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/* frees an area <area> of size <size> allocated by pool_alloc_area(). The
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* semantics are identical to free() except that the size is specified and
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* may be ignored.
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*/
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static forceinline void pool_free_area(void *area, size_t __maybe_unused size)
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{
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will_free(area, size);
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free(area);
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}
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/************* use-after-free allocator *************/
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/* allocates an area of size <size> and returns it. The semantics are similar
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* to those of malloc(). However the allocation is rounded up to 4kB so that a
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* full page is allocated. This ensures the object can be freed alone so that
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* future dereferences are easily detected. The returned object is always
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* 16-bytes aligned to avoid issues with unaligned structure objects. In case
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* some padding is added, the area's start address is copied at the end of the
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* padding to help detect underflows.
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*/
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static inline void *pool_alloc_area_uaf(size_t size)
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{
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size_t pad = (4096 - size) & 0xFF0;
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void *ret;
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ret = mmap(NULL, (size + 4095) & -4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
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if (ret != MAP_FAILED) {
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/* let's dereference the page before returning so that the real
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* allocation in the system is performed without holding the lock.
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*/
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*(int *)ret = 0;
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if (pad >= sizeof(void *))
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*(void **)(ret + pad - sizeof(void *)) = ret + pad;
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ret += pad;
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} else {
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ret = NULL;
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}
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return ret;
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}
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/* frees an area <area> of size <size> allocated by pool_alloc_area_uaf(). The
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* semantics are identical to free() except that the size must absolutely match
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* the one passed to pool_alloc_area_uaf(). In case some padding is added, the
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* area's start address is compared to the one at the end of the padding, and
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* a segfault is triggered if they don't match, indicating an underflow.
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*/
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static inline void pool_free_area_uaf(void *area, size_t size)
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{
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size_t pad = (4096 - size) & 0xFF0;
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/* This object will be released for real in order to detect a use after
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* free. We also force a write to the area to ensure we crash on double
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* free or free of a const area.
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*/
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*(uint32_t *)area = 0xDEADADD4;
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if (pad >= sizeof(void *) && *(void **)(area - sizeof(void *)) != area)
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ABORT_NOW();
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munmap(area - pad, (size + 4095) & -4096);
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}
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#endif /* _HAPROXY_POOL_OS_H */
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/*
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* Local variables:
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* c-indent-level: 8
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* c-basic-offset: 8
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* End:
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*/
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