From 3e10c3ecfcaf604d8b400d6e463e1a186ce97d9b Mon Sep 17 00:00:00 2001 From: Gonglei Date: Fri, 2 Sep 2016 11:58:18 +0800 Subject: [PATCH] vnc: fix qemu crash because of SIGSEGV MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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=, 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=, h=) at ui/console.c:2111 0x00007f0b77ac0980 in cirrus_do_copy (h=, w=, src=, dst=, 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=, size=1, shift=,mask=, 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=, access_size_max=, access=access@entry=0x7f0b77965c80 , 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 ) at /root/rpmbuild/BUILD/master/qemu/exec.c:2544 address_space_write (as=, addr=, attrs=..., buf=, len=) at /root/rpmbuild/BUILD/master/qemu/exec.c:2601 0x00007f0b77925c1d in address_space_rw (as=, addr=, attrs=..., attrs@entry=..., buf=buf@entry=0x7f0b77713028 "\002\377\377\377", len=, is_write=) 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. Cc: Gerd Hoffmann Cc: Daniel P. Berrange Reported-by: Yanying Zhuang Signed-off-by: Gonglei Reviewed-by: Marc-André Lureau Message-id: 1472788698-120964-1-git-send-email-arei.gonglei@huawei.com Signed-off-by: Gerd Hoffmann --- ui/vnc.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/ui/vnc.c b/ui/vnc.c index d1087c93a5..76a3273e0b 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);