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[Qemu-devel] [PATCH repost 2/4] oslib: allocate PROT_NONE pages on top o
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] [PATCH repost 2/4] oslib: allocate PROT_NONE pages on top of RAM |
Date: |
Sun, 27 Sep 2015 13:14:34 +0300 |
This inserts a read and write protected page between RAM and QEMU
memory. This makes it harder to exploit QEMU bugs resulting from buffer
overflows in devices using variants of cpu_physical_memory_map,
dma_memory_map etc.
Signed-off-by: Michael S. Tsirkin <address@hidden>
---
util/oslib-posix.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 27972d4..a0fcdc2 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -128,7 +128,7 @@ void *qemu_memalign(size_t alignment, size_t size)
void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment)
{
size_t align = QEMU_VMALLOC_ALIGN;
- size_t total = size + align - getpagesize();
+ size_t total = size + align;
void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
void *ptr1;
@@ -154,8 +154,8 @@ void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment)
if (offset > 0) {
munmap(ptr - offset, offset);
}
- if (total > size) {
- munmap(ptr + size, total - size);
+ if (total > size + getpagesize()) {
+ munmap(ptr + size + getpagesize(), total - size - getpagesize());
}
trace_qemu_anon_ram_alloc(size, ptr);
@@ -172,7 +172,7 @@ void qemu_anon_ram_free(void *ptr, size_t size)
{
trace_qemu_anon_ram_free(ptr, size);
if (ptr) {
- munmap(ptr, size);
+ munmap(ptr, size + getpagesize());
}
}
--
MST