On 2016/9/2 16:38, Marc-André Lureau wrote:
> Hi
>
> On Fri, Sep 2, 2016 at 8:00 AM Gonglei <arei.gong...@huawei.com
> <mailto:arei.gong...@huawei.com>> wrote:
>
> The backtrace is:
>
> 0x00007f0b75cdf880 in pixman_image_get_stride () from
> /lib64/libpixman-1.so.0
> 0x00007f0b77bcb3cf in vnc_server_fb_stride (vd=0x7f0b7a1a2bb0) at
> ui/vnc.c:680
> vnc_dpy_copy (dcl=0x7f0b7a1a2c00, src_x=224, src_y=263, dst_x=319,
> dst_y=363, w=1, h=1) at ui/vnc.c:915
> 0x00007f0b77bbcc35 in dpy_gfx_copy (con=0x7f0b7a146210,
> src_x=src_x@entry=224, src_y=src_y@entry=263, dst_x=dst_x@entry=319,
> dst_y=dst_y@entry=363, w=1, h=1) at ui/console.c:1575
> 0x00007f0b77bbda4e in qemu_console_copy (con=<optimized out>,
> src_x=src_x@entry=224, src_y=src_y@entry=263, dst_x=dst_x@entry=319,
> dst_y=dst_y@entry=363, w=<optimized out>, h=<optimized out>) at
> ui/console.c:2111
> 0x00007f0b77ac0980 in cirrus_do_copy (h=<optimized out>, w=<optimized
> out>, src=<optimized out>, dst=<optimized out>, s=0x7f0b7b086090) at
> hw/display/cirrus_vga.c:774
> cirrus_bitblt_videotovideo_copy (s=0x7f0b7b086090) at
> hw/display/cirrus_vga.c:793
> cirrus_bitblt_videotovideo (s=0x7f0b7b086090) at
> hw/display/cirrus_vga.c:915
> cirrus_bitblt_start (s=0x7f0b7b086090) at hw/display/cirrus_vga.c:1056
> 0x00007f0b77965cfb in memory_region_write_accessor (mr=0x7f0b7b096e40,
> addr=320, value=<optimized out>, size=1, shift=<optimized
> out>,mask=<optimized out>, attrs=...) at
> /root/rpmbuild/BUILD/master/qemu/memory.c:525
> 0x00007f0b77963f59 in access_with_adjusted_size (addr=addr@entry=320,
> value=value@entry=0x7f0b69a268d8, size=size@entry=4,
> access_size_min=<optimized out>, access_size_max=<optimized out>,
> access=access@entry=0x7f0b77965c80 <memory_region_write_accessor>,
> mr=mr@entry=0x7f0b7b096e40, attrs=attrs@entry=...) at
> /root/rpmbuild/BUILD/master/qemu/memory.c:591
> 0x00007f0b77968315 in memory_region_dispatch_write
> (mr=mr@entry=0x7f0b7b096e40, addr=addr@entry=320, data=18446744073709551362,
> size=size@entry=4, attrs=attrs@entry=...) at
> /root/rpmbuild/BUILD/master/qemu/memory.c:1262
> 0x00007f0b779256a9 in address_space_write_continue (mr=0x7f0b7b096e40,
> l=4, addr1=320, len=4, buf=0x7f0b77713028 "\002\377\377\377",
> attrs=..., addr=4273930560, as=0x7f0b7827d280 <address_space_memory>) at
> /root/rpmbuild/BUILD/master/qemu/exec.c:2544
> address_space_write (as=<optimized out>, addr=<optimized out>, attrs=...,
> buf=<optimized out>, len=<optimized out>) at
> /root/rpmbuild/BUILD/master/qemu/exec.c:2601
> 0x00007f0b77925c1d in address_space_rw (as=<optimized out>,
> addr=<optimized out>, attrs=..., attrs@entry=...,
> buf=buf@entry=0x7f0b77713028 "\002\377\377\377", len=<optimized out>,
> is_write=<optimized out>) at /root/rpmbuild/BUILD/master/qemu/exec.c:2703
> 0x00007f0b77962f53 in kvm_cpu_exec (cpu=cpu@entry=0x7f0b79fcc2d0) at
> /root/rpmbuild/BUILD/master/qemu/kvm-all.c:1965
> 0x00007f0b77950cc6 in qemu_kvm_cpu_thread_fn (arg=0x7f0b79fcc2d0) at
> /root/rpmbuild/BUILD/master/qemu/cpus.c:1078
> 0x00007f0b744b3dc5 in start_thread (arg=0x7f0b69a27700) at
> pthread_create.c:308
> 0x00007f0b70d3d66d in clone () from /lib64/libc.so.6
>
> The code path while meeting segfault:
> vnc_dpy_copy
> vnc_update_client
> vnc_disconnect_finish [while vnc_disconnect_start() is invoked
> because somethins wrong]
> vnc_update_server_surface
> vd->server = NULL;
> vnc_server_fb_stride
> pixman_image_get_stride(vd->server)
>
> Let's add a non-NULL check before calling vnc_server_fb_stride() to avoid
> segmentation fault.
>
>
> Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com>
>
Thanks.
> (It would be great if you had a reproducer)
>
1.using VNC Viewer client tool.
2.using SUSE 11.3 as guest VM with graphic console.
3.connecting vnc as soon as possible after starting the VM.
I get the below information before qemu crash.
[New Thread 0x7ffee93ff700 (LWP 18570)]
[Switching to Thread 0x7fffea305700 (LWP 17105)]
Breakpoint 1, vnc_client_io_error (vs=0x5555581025a0, ret=-2,
errp=0x7fffea3045b0) at ui/vnc.c:1262
1262 vnc_disconnect_start(vs);
(gdb) bt
#0 vnc_client_io_error (vs=0x5555581025a0, ret=-2, errp=0x7fffea3045b0) at
ui/vnc.c:1262
#1 0x00005555559fce2b in vnc_client_write_buf (vs=0x5555581025a0,
data=<optimized out>, datalen=<optimized out>) at ui/vnc.c:1302
#2 0x00005555559fcee6 in vnc_client_write_plain (vs=<optimized out>) at
ui/vnc.c:1333
#3 vnc_client_write_locked (vs=0x5555581025a0) at ui/vnc.c:1366
#4 0x00005555559fd901 in vnc_flush (vs=0x5555581025a0) at ui/vnc.c:1557
#5 0x00005555559fe6ea in vnc_copy (h=210, w=472, dst_y=261, dst_x=222,
src_y=279, src_x=276, vs=0x5555581025a0) at ui/vnc.c:886
#6 vnc_dpy_copy (dcl=0x5555570b0c50, src_x=276, src_y=279, dst_x=222,
dst_y=261, w=472, h=210) at ui/vnc.c:965
#7 0x00005555559efc35 in dpy_gfx_copy (con=0x5555570a6030,
src_x=src_x@entry=276, src_y=src_y@entry=279, dst_x=dst_x@entry=222,
dst_y=dst_y@entry=261, w=472, h=210) at ui/console.c:1575
#8 0x00005555559f0a4e in qemu_console_copy (con=<optimized out>,
src_x=src_x@entry=276, src_y=src_y@entry=279, dst_x=dst_x@entry=222,
dst_y=dst_y@entry=261, w=<optimized out>, h=<optimized out>) at
ui/console.c:2111
#9 0x00005555558f3980 in cirrus_do_copy (h=<optimized out>, w=<optimized out>,
src=<optimized out>, dst=<optimized out>, s=0x555557f94090)
at hw/display/cirrus_vga.c:774
#10 cirrus_bitblt_videotovideo_copy (s=0x555557f94090) at
hw/display/cirrus_vga.c:793
#11 cirrus_bitblt_videotovideo (s=0x555557f94090) at hw/display/cirrus_vga.c:915
#12 cirrus_bitblt_start (s=0x555557f94090) at hw/display/cirrus_vga.c:1056
#13 0x0000555555798cfb in memory_region_write_accessor (mr=0x555557fa4e40,
addr=320, value=<optimized out>, size=1, shift=<optimized out>,
mask=<optimized out>, attrs=...) at
/root/rpmbuild/BUILD/master/qemu/memory.c:525
#14 0x0000555555796f59 in access_with_adjusted_size (addr=addr@entry=320,
value=value@entry=0x7fffea3048d8, size=size@entry=4,
access_size_min=<optimized out>, access_size_max=<optimized out>,
access=access@entry=0x555555798c80 <memory_region_write_accessor>,
mr=mr@entry=0x555557fa4e40, attrs=attrs@entry=...) at
/root/rpmbuild/BUILD/master/qemu/memory.c:591
#15 0x000055555579b315 in memory_region_dispatch_write
(mr=mr@entry=0x555557fa4e40, addr=addr@entry=320, data=18446744073709551362,
size=size@entry=4, attrs=attrs@entry=...) at
/root/rpmbuild/BUILD/master/qemu/memory.c:1262
#16 0x00005555557586a9 in address_space_write_continue (mr=0x555557fa4e40, l=4,
addr1=320, len=4, buf=0x7ffff7fef028 "\002\377\377\377",
attrs=..., addr=4273930560, as=0x5555560b0280 <address_space_memory>) at
/root/rpmbuild/BUILD/master/qemu/exec.c:2544
#17 address_space_write (as=<optimized out>, addr=<optimized out>, attrs=...,
buf=<optimized out>, len=<optimized out>)
at /root/rpmbuild/BUILD/master/qemu/exec.c:2601
#18 0x0000555555758c1d in address_space_rw (as=<optimized out>, addr=<optimized
out>, attrs=..., attrs@entry=...,
buf=buf@entry=0x7ffff7fef028 "\002\377\377\377", len=<optimized out>,
is_write=<optimized out>)
at /root/rpmbuild/BUILD/master/qemu/exec.c:2703
#19 0x0000555555795f53 in kvm_cpu_exec (cpu=cpu@entry=0x555556eda340) at
/root/rpmbuild/BUILD/master/qemu/kvm-all.c:1965
#20 0x0000555555783cc6 in qemu_kvm_cpu_thread_fn (arg=0x555556eda340) at
/root/rpmbuild/BUILD/master/qemu/cpus.c:1078
#21 0x00007ffff4d91dc5 in start_thread (arg=0x7fffea305700) at
pthread_create.c:308
#22 0x00007ffff161b66d in clone () from /lib64/libc.so.6
(gdb)
ssize_t vnc_client_write_buf(VncState *vs, const uint8_t *data, size_t datalen)
{
Error *err = NULL;
ssize_t ret;
ret = qio_channel_write(
vs->ioc, (const char *)data, datalen, &err);
VNC_DEBUG("Wrote wire %p %zd -> %ld\n", data, datalen, ret);
return vnc_client_io_error(vs, ret, &err);
}
Please notes that the qio_channel_write() return -2.
> It looks like this is not a regression from 2.7, perhaps it should be
> post-poned?
>
Yes, it's not a regression from 2.7, but it indeed is a serious bug and the fix
is harmless. :)
Regards,
-Gonglei
> Cc: Gerd Hoffmann <kra...@redhat.com <mailto:kra...@redhat.com>>
> Cc: Daniel P. Berrange <berra...@redhat.com <mailto:berra...@redhat.com>>
> Reported-by: Yanying Zhuang <ann.zhuangyany...@huawei.com
> <mailto:ann.zhuangyany...@huawei.com>>
> Signed-off-by: Gonglei <arei.gong...@huawei.com
> <mailto:arei.gong...@huawei.com>>
> ---
> ui/vnc.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/ui/vnc.c b/ui/vnc.c
> index d1087c9..76a3273 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -911,6 +911,10 @@ static void vnc_dpy_copy(DisplayChangeListener *dcl,
> }
> }
>
> + if (!vd->server) {
> + /* no client connected */
> + return;
> + }
> /* do bitblit op on the local surface too */
> pitch = vnc_server_fb_stride(vd);
> src_row = vnc_server_fb_ptr(vd, src_x, src_y);
> --
> 1.7.12.4
>
>
>
> --
> Marc-André Lureau
