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Re: [Qemu-devel] [PATCH for 2.1] qemu_opts_append: Play nicely with Qemu
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH for 2.1] qemu_opts_append: Play nicely with QemuOptsList's head |
Date: |
Wed, 25 Jun 2014 07:46:32 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 |
On 06/25/2014 02:38 AM, Michal Privoznik wrote:
> When running a libvirt test suite I've noticed the qemu-img is
> crashing occasionally. Tracing the problem down led me to the
> following valgrind output:
Thanks for tracking this! It has been reported in other threads, but
yours is the first patch.
> The problem is apparently in the qemu_opts_append(). Well, if it
> gets called twice or more. On the first call, when @dst is NULL
> some initialization is done during which @dst->head list gets
> initialized. The list is initialized in a way, so that the list
> tail points at the list head. However, the next time
> qemu_opts_append() is called for new options to be added,
> g_realloc() may move @dst at new address making the old list tail
s/at new/to a new/
> point at invalid address. If that's the case we must update the
> list pointers.
>
> Signed-off-by: Michal Privoznik <address@hidden>
> ---
> util/qemu-option.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
Reviewed-by: Eric Blake <address@hidden>
> + need_head_update = true;
> + } else {
> + /* Moreover, even if dst is not NULL, the realloc may move it at a
s/at/to/
> + * different address in which case we may get a stale tail pointer
> + * in dst->head. */
> + need_head_update = QTAILQ_EMPTY(&dst->head);
> }
>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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