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exec: Stop using memory after free

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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.

Signed-off-by: Don Slutz <Don.Slutz@Gmail.com>
Message-Id: <1448921464-21845-1-git-send-email-Don.Slutz@Gmail.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Don Slutz 2015-11-30 17:11:04 -05:00 committed by Paolo Bonzini
parent 9d7b969ea6
commit 55b4e80b04
1 changed files with 3 additions and 1 deletions
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exec.c
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@ -1064,9 +1064,11 @@ static uint16_t phys_section_add(PhysPageMap *map,
static void phys_section_destroy(MemoryRegion *mr) static void phys_section_destroy(MemoryRegion *mr)
{ {
bool have_sub_page = mr->subpage;
memory_region_unref(mr); memory_region_unref(mr);
if (mr->subpage) { if (have_sub_page) {
subpage_t *subpage = container_of(mr, subpage_t, iomem); subpage_t *subpage = container_of(mr, subpage_t, iomem);
object_unref(OBJECT(&subpage->iomem)); object_unref(OBJECT(&subpage->iomem));
g_free(subpage); g_free(subpage);