Re: [Qemu-devel] segmentation fault in qemu-kvm-0.14.0

[Stefan Weil <weil@mail.berlios.de>]

Am 08.03.2011 23:53, schrieb Peter Lieven:
> Hi,
>
> during testing of qemu-kvm-0.14.0 i can reproduce the following 
> segfault. i have seen similar crash already in 0.13.0, but had no time 
> to debug.
> my guess is that this segfault is related to the threaded vnc server 
> which was introduced in qemu 0.13.0. the bug is only triggerable if a vnc
> client is attached. it might also be connected to a resolution change 
> in the guest. i have a backtrace attached. the debugger is still 
> running if someone
> needs more output
>
> Reading symbols from /usr/local/bin/qemu-system-x86_64...done.
> (gdb) r -net tap,vlan=141,script=no,downscript=no,ifname=tap0 -net 
> nic,vlan=141,model=rtl8139,macaddr=52:54:00:ff:00:93 -drive 
> format=host_device,file=/dev/mapper/iqn.2001-05.co
> m.equallogic:0-8a0906-e6b70e107-e87000e7acf4d4e5-lieven-winxp-r17453,if=ide,boot=on,cache=none,aio=native 
> -m 1024 -monitor tcp:0:4001,server,nowait -vnc :1 -name 'lieven-winxp-te
> st' -boot order=c,menu=on -k de -pidfile /var/run/qemu/vm-265.pid 
> -mem-path /hugepages -mem-prealloc -cpu qemu64,model_id='Intel(R) 
> Xeon(R) CPU E5640 @ 2.67GHz',-n
> x -rtc base=localtime,clock=vm -vga cirrus -usb -usbdevice tablet
> Starting program: /usr/local/bin/qemu-system-x86_64 -net 
> tap,vlan=141,script=no,downscript=no,ifname=tap0 -net 
> nic,vlan=141,model=rtl8139,macaddr=52:54:00:ff:00:93 -drive format
> =host_device,file=/dev/mapper/iqn.2001-05.com.equallogic:0-8a0906-e6b70e107-e87000e7acf4d4e5-lieven-winxp-r17453,if=ide,boot=on,cache=none,aio=native 
> -m 1024 -monitor tcp:0:4001,
> server,nowait -vnc :1 -name 'lieven-winxp-test' -boot order=c,menu=on 
> -k de -pidfile /var/run/qemu/vm-265.pid -mem-path /hugepages 
> -mem-prealloc -cpu qemu64,model_id='Intel(R
> ) Xeon(R) CPU E5640 @ 2.67GHz',-nx -rtc base=localtime,clock=vm -vga 
> cirrus -usb -usbdevice tablet
> [Thread debugging using libthread_db enabled]
>
> [New Thread 0x7ffff694e700 (LWP 29042)]
> [New Thread 0x7ffff6020700 (LWP 29043)]
> [New Thread 0x7ffff581f700 (LWP 29074)]
> [Thread 0x7ffff581f700 (LWP 29074) exited]
> [New Thread 0x7ffff581f700 (LWP 29124)]
> [Thread 0x7ffff581f700 (LWP 29124) exited]
> [New Thread 0x7ffff581f700 (LWP 29170)]
> [Thread 0x7ffff581f700 (LWP 29170) exited]
> [New Thread 0x7ffff581f700 (LWP 29246)]
> [Thread 0x7ffff581f700 (LWP 29246) exited]
> [New Thread 0x7ffff581f700 (LWP 29303)]
> [Thread 0x7ffff581f700 (LWP 29303) exited]
> [New Thread 0x7ffff581f700 (LWP 29349)]
> [Thread 0x7ffff581f700 (LWP 29349) exited]
> [New Thread 0x7ffff581f700 (LWP 29399)]
> [Thread 0x7ffff581f700 (LWP 29399) exited]
> [New Thread 0x7ffff581f700 (LWP 29471)]
> [Thread 0x7ffff581f700 (LWP 29471) exited]
> [New Thread 0x7ffff581f700 (LWP 29521)]
> [Thread 0x7ffff581f700 (LWP 29521) exited]
> [New Thread 0x7ffff581f700 (LWP 29593)]
> [Thread 0x7ffff581f700 (LWP 29593) exited]
> [New Thread 0x7ffff581f700 (LWP 29703)]
> [Thread 0x7ffff581f700 (LWP 29703) exited]
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x0000000000000000 in ?? ()
> (gdb)
>
> (gdb) thread apply all bt full
>
> Thread 3 (Thread 0x7ffff6020700 (LWP 29043)):
> #0 0x00007ffff79c385c in pthread_cond_wait@@GLIBC_2.3.2 ()
> from /lib/libpthread.so.0
> No symbol table info available.
> #1 0x00000000004d3ae1 in qemu_cond_wait (cond=0x1612d50, mutex=0x1612d80)
> at qemu-thread.c:133
> err = 0
> __func__ = "qemu_cond_wait"
> #2 0x00000000004d2b39 in vnc_worker_thread_loop (queue=0x1612d50)
> at ui/vnc-jobs-async.c:198
> job = 0x7ffff058cd20
> entry = 0x0
> tmp = 0x0
> vs = {csock = -1, ds = 0x15cb380, dirty = {{0, 0, 0, 0,
> 0} <repeats 2048 times>}, vd = 0x1607ff0, need_update = 0,
> force_update = 0, features = 243, absolute = 0, last_x = 0,
> last_y = 0, client_width = 0, client_height = 0, vnc_encoding = 7,
> major = 0, minor = 0, challenge = '\000' <repeats 15 times>,
> info = 0x0, output = {capacity = 3194, offset = 2723,
> buffer = 0x1fbbfd0 ""}, input = {capacity = 0, offset = 0,
> buffer = 0x0}, write_pixels = 0x4c4bc9 <vnc_write_pixels_generic>,
> clientds = {flags = 0 '\000', width = 720, height = 400,
> linesize = 2880,
> data = 0x7ffff6021010 <Address 0x7ffff6021010 out of bounds>,
> pf = {bits_per_pixel = 32 ' ', bytes_per_pixel = 4 '\004',
> depth = 24 '\030', rmask = 0, gmask = 0, bmask = 0, amask = 0,
> rshift = 16 '\020', gshift = 8 '\b', bshift = 0 '\000',
> ashift = 24 '\030', rmax = 255 '\377', gmax = 255 '\377',
> bmax = 255 '\377', amax = 255 '\377', rbits = 8 '\b',
> gbits = 8 '\b', bbits = 8 '\b', abits = 8 '\b'}},
> audio_cap = 0x0, as = {freq = 0, nchannels = 0, fmt = AUD_FMT_U8,
> endianness = 0}, read_handler = 0, read_handler_expect = 0,
> modifiers_state = '\000' <repeats 255 times>, led = 0x0,
> abort = false, output_mutex = {lock = {__data = {__lock = 0,
> __count = 0, __owner = 0, __nusers = 0, __kind = 0,
> __spins = 0, __list = {__prev = 0x0, __next = 0x0}},
> __size = '\000' <repeats 39 times>, __align = 0}}, tight = {
> type = 7, quality = 255 '\377', compression = 9 '\t',
> pixel24 = 1 '\001', tight = {capacity = 3146708, offset = 1376,
> buffer = 0x7ffff4684010 ""}, tmp = {capacity = 3194,
> offset = 2672, buffer = 0x1fbbfd0 ""}, zlib = {
> capacity = 141451, offset = 0,
> buffer = 0x1805da0 
> "B--G\317\253\031=\257f\364\274\232\321\363jF\317\253\241\326y5"}, 
> gradient = {capacity = 0, offset = 0, buffer = 0x0},
> levels = {9, 9, 9, 0}, stream = {{
> next_in = 0x7ffff4684460 
> "\002\003\002\003\002\002\002\002\002\002\002\002\002", avail_in = 0, 
> total_in = 9048240,
> next_out = 0x1805df6 
> "d\276\345c\363\216\237\212\377\314\003\236\246\\$\361\025~\032\311\232\067q&_$\231\251y\262*!\231\067\236\067\363\214\347\315\240\361\221,\274T\257\221\314\333\341\251\362R\373\232_\311a\272\002\061sgt\317\030\332\262~\300\063\267]\307\267\343\033", 
> avail_out = 141365,
> total_out = 1034664, msg = 0x0, state = 0x16ea550,
> zalloc = 0x4ca2d8 <vnc_zlib_zalloc>,
> zfree = 0x4ca315 <vnc_zlib_zfree>, opaque = 0x7ffff6015920,
> data_type = 0, adler = 1285581469, reserved = 0}, {
> next_in = 0x7ffff4684022 "\002\002", avail_in = 0,
> total_in = 46491,
> next_out = 0x1805da8 "\257f\364\274\232\321\363jF\317\253\241\326y5", 
> avail_out = 141443, total_out = 9905, msg = 0x0, state = 0x17a3f00,
> zalloc = 0x4ca2d8 <vnc_zlib_zalloc>,
> zfree = 0x4ca315 <vnc_zlib_zfree>, opaque = 0x7ffff6015920,
> data_type = 0, adler = 2415253306, reserved = 0}, {
> next_in = 0x7ffff4684570 "\017(`", avail_in = 0,
> total_in = 2188024,
> next_out = 0x1805dbd 
> "z\222\024#\233O\214g\341\352\211/U\310s\017\361\245\020\262\343\211TO\222\371\304\207\fryK|\251E\222\343\311+\237\351`>\355\312sR\265\320\272~\001", 
> avail_out = 141422, total_out = 100512, msg = 0x0,
> state = 0x1682950, zalloc = 0x4ca2d8 <vnc_zlib_zalloc>,
> zfree = 0x4ca315 <vnc_zlib_zfree>, opaque = 0x7ffff6015920,
> data_type = 0, adler = 3999694267, reserved = 0}, {
> next_in = 0x0, avail_in = 0, total_in = 0, next_out = 0x0,
> avail_out = 0, total_out = 0, msg = 0x0, state = 0x0,
> zalloc = 0, zfree = 0, opaque = 0x0, data_type = 0, adler = 0,
> reserved = 0}}}, zlib = {zlib = {capacity = 0, offset = 0,
> buffer = 0x0}, tmp = {capacity = 0, offset = 0, buffer = 0x0},
> stream = {next_in = 0x0, avail_in = 0, total_in = 0,
> next_out = 0x0, avail_out = 0, total_out = 0, msg = 0x0,
> state = 0x0, zalloc = 0, zfree = 0, opaque = 0x0, data_type = 0,
> adler = 0, reserved = 0}, level = 0}, hextile = {
> send_tile = 0x4cd21d <send_hextile_tile_generic_32>},
> mouse_mode_notifier = {notify = 0x80, node = {tqe_next = 0x1612da8,
> tqe_prev = 0x7ffff6020700}}, next = {tqe_next = 0x7ffff6020700,
> tqe_prev = 0x7ffff7ffe128}}
> n_rectangles = 40
> saved_offset = 2
> flush = true
> #3 0x00000000004d302c in vnc_worker_thread (arg=0x1612d50)
> at ui/vnc-jobs-async.c:302
> queue = 0x1612d50
> #4 0x00007ffff79be9ca in start_thread () from /lib/libpthread.so.0
> No symbol table info available.
> #5 0x00007ffff6c3970d in clone () from /lib/libc.so.6
> No symbol table info available.
> #6 0x0000000000000000 in ?? ()
> No symbol table info available.
>
> Thread 2 (Thread 0x7ffff694e700 (LWP 29042)):
> #0 0x00007ffff6c31197 in ioctl () from /lib/libc.so.6
> No symbol table info available.
> #1 0x0000000000434c12 in kvm_run (env=0x118c2e0)
> at /usr/src/qemu-kvm-0.14.0/qemu-kvm.c:582
> r = 0
> kvm = 0x1172538
> run = 0x7ffff7fc7000
> fd = 15
> #2 0x0000000000435ed4 in kvm_cpu_exec (env=0x118c2e0)
> at /usr/src/qemu-kvm-0.14.0/qemu-kvm.c:1233
> r = 0
> #3 0x00000000004364f7 in kvm_main_loop_cpu (env=0x118c2e0)
> at /usr/src/qemu-kvm-0.14.0/qemu-kvm.c:1419
> run_cpu = 1
> #4 0x0000000000436640 in ap_main_loop (_env=0x118c2e0)
> at /usr/src/qemu-kvm-0.14.0/qemu-kvm.c:1466
> env = 0x118c2e0
> signals = {__val = {18446744067267100671,
> 18446744073709551615 <repeats 15 times>}}
> data = 0x0
> #5 0x00007ffff79be9ca in start_thread () from /lib/libpthread.so.0
> No symbol table info available.
> #6 0x00007ffff6c3970d in clone () from /lib/libc.so.6
> No symbol table info available.
> #7 0x0000000000000000 in ?? ()
> No symbol table info available.
>
> Thread 1 (Thread 0x7ffff7ff0700 (LWP 29038)):
> #0 0x0000000000000000 in ?? ()
> No symbol table info available.
> #1 0x000000000041d669 in main_loop_wait (nonblocking=0)
> at /usr/src/qemu-kvm-0.14.0/vl.c:1388
> pioh = 0x1652870
> ioh = 0x1613330
> rfds = {fds_bits = {0 <repeats 16 times>}}
> wfds = {fds_bits = {1048576, 0 <repeats 15 times>}}
> xfds = {fds_bits = {0 <repeats 16 times>}}
> ret = 1
> nfds = 21
> tv = {tv_sec = 0, tv_usec = 999998}
> timeout = 1000
> #2 0x0000000000436a4a in kvm_main_loop ()
> at /usr/src/qemu-kvm-0.14.0/qemu-kvm.c:1589
> mask = {__val = {268443712, 0 <repeats 15 times>}}
> sigfd = 19
> #3 0x000000000041d785 in main_loop () at 
> /usr/src/qemu-kvm-0.14.0/vl.c:1429
> r = 0
> #4 0x000000000042166a in main (argc=33, argv=0x7fffffffe658,
> envp=0x7fffffffe768) at /usr/src/qemu-kvm-0.14.0/vl.c:3201
> gdbstub_dev = 0x0
> i = 64
> snapshot = 0
> linux_boot = 0
> icount_option = 0x0
> initrd_filename = 0x0
> kernel_filename = 0x0
> kernel_cmdline = 0x5e57a3 ""
> boot_devices = "c\000d", '\000' <repeats 29 times>
> ds = 0x15cb380
> dcl = 0x0
> cyls = 0
> heads = 0
> secs = 0
> translation = 0
> hda_opts = 0x0
> opts = 0x1171a80
> olist = 0x7fffffffe3f0
> optind = 33
> optarg = 0x7fffffffebce "tablet"
> loadvm = 0x0
> machine = 0x962cc0
> cpu_model = 0x7fffffffeb51 "qemu64,model_id=Intel(R) Xeon(R) CPU", ' ' 
> <repeats 11 times>, "E5640 @ 2.67GHz,-nx"
> tb_size = 0
> pid_file = 0x7fffffffeb10 "/var/run/qemu/vm-265.pid"
> incoming = 0x0
> show_vnc_port = 0
> defconfig = 1
> (gdb) info threads
> 3 Thread 0x7ffff6020700 (LWP 29043) 0x00007ffff79c385c in 
> pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
> 2 Thread 0x7ffff694e700 (LWP 29042) 0x00007ffff6c31197 in ioctl ()
> from /lib/libc.so.6
> * 1 Thread 0x7ffff7ff0700 (LWP 29038) 0x0000000000000000 in ?? ()
> (gdb)
>
>
> Help appreciated!
>
> Thanks,
> Peter

Hi Peter,

did you apply this patch which fixes one of the known vnc problems
(but is still missing in qemu git master):

http://lists.nongnu.org/archive/html/qemu-devel/2011-03/msg00256.html

Then you can read this thread:

http://lists.nongnu.org/archive/html/qemu-devel/2011-03/msg00313.html

And finally the following modifications of ui/vnc.c might help to see
whether you experience the same kind of crash as I get here in
my environment. They add assertions for bad memory access
which occurs sometimes when a vnc client-server connection exists and
the screen is refreshed after a resolution change.
The code line with the //~ comment also includes a fix which
works for me.

Regards,
Stefan W.

@@ -2382,6 +2384,10 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
      int y;
      uint8_t *guest_row;
      uint8_t *server_row;
+
+    size_t guest_size = vd->guest.ds->linesize * vd->guest.ds->height;
+    size_t server_size = vd->server->linesize * vd->server->height;
+
      int cmp_bytes;
      VncState *vs;
      int has_dirty = 0;
@@ -2399,11 +2405,15 @@ static int vnc_refresh_server_surface(VncDisplay 
*vd)
       * Update server dirty map.
       */
      cmp_bytes = 16 * ds_get_bytes_per_pixel(vd->ds);
+    if (cmp_bytes > vd->ds->surface->linesize) {
+        //~ fix crash: cmp_bytes = vd->ds->surface->linesize;
+    }
      guest_row  = vd->guest.ds->data;
      server_row = vd->server->data;
      for (y = 0; y < vd->guest.ds->height; y++) {
          if (!bitmap_empty(vd->guest.dirty[y], VNC_DIRTY_BITS)) {
              int x;
+            size_t size_offset = 0;
              uint8_t *guest_ptr;
              uint8_t *server_ptr;

@@ -2412,6 +2422,9 @@ static int vnc_refresh_server_surface(VncDisplay *vd)

              for (x = 0; x < vd->guest.ds->width;
                      x += 16, guest_ptr += cmp_bytes, server_ptr += 
cmp_bytes) {
+                assert(size_offset + cmp_bytes <= guest_size);
+                assert(size_offset + cmp_bytes <= server_size);
+                size_offset += cmp_bytes;
                  if (!test_and_clear_bit((x / 16), vd->guest.dirty[y]))
                      continue;
                  if (memcmp(server_ptr, guest_ptr, cmp_bytes) == 0)
@@ -2427,6 +2440,10 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
          }
          guest_row  += ds_get_linesize(vd->ds);
          server_row += ds_get_linesize(vd->ds);
+        assert(guest_size >= ds_get_linesize(vd->ds));
+        guest_size -= ds_get_linesize(vd->ds);
+        assert(server_size >= ds_get_linesize(vd->ds));
+        server_size -= ds_get_linesize(vd->ds);
      }
      return has_dirty;
  }