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Re: [Qemu-devel] [PATCH] exec: Stop using memory after free
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] exec: Stop using memory after free |
Date: |
Tue, 1 Dec 2015 10:52:14 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 30/11/2015 23:11, Don Slutz wrote:
> memory_region_unref(mr) can free memory.
>
> For example I got:
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x7f43280d4700 (LWP 4462)]
> 0x00007f43323283c0 in phys_section_destroy (mr=0x7f43259468b0)
> at /home/don/xen/tools/qemu-xen-dir/exec.c:1023
> 1023 if (mr->subpage) {
> (gdb) bt
> at /home/don/xen/tools/qemu-xen-dir/exec.c:1023
> at /home/don/xen/tools/qemu-xen-dir/exec.c:1034
> at /home/don/xen/tools/qemu-xen-dir/exec.c:2205
> (gdb) p mr
> $1 = (MemoryRegion *) 0x7f43259468b0
>
> And this change prevents this.
Great, thanks! I think this fixes also the problem that Gonglei was
seeing a few months ago. I'll queue it for 2.5.
BTW, since I have your attention, have you noticed my refresh/rewrite of
your SAS1068 patches? A review would be welcome.
Paolo
> Signed-off-by: Don Slutz <address@hidden>
> ---
> exec.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/exec.c b/exec.c
> index de1cf19..0bf0a6e 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1064,9 +1064,11 @@ static uint16_t phys_section_add(PhysPageMap *map,
>
> static void phys_section_destroy(MemoryRegion *mr)
> {
> + bool have_sub_page = mr->subpage;
> +
> memory_region_unref(mr);
>
> - if (mr->subpage) {
> + if (have_sub_page) {
> subpage_t *subpage = container_of(mr, subpage_t, iomem);
> object_unref(OBJECT(&subpage->iomem));
> g_free(subpage);
>
- Re: [Qemu-devel] [PATCH] exec: Stop using memory after free,
Paolo Bonzini <=