On Tue, Jan 7, 2020 at 2:06 PM Eryu Guan <[email protected]> wrote: > > On Thu, Jan 02, 2020 at 10:08:50AM +0800, Eryu Guan wrote: > > On Tue, Dec 31, 2019 at 11:51:35AM +0100, Igor Mammedov wrote: > > > On Tue, 31 Dec 2019 18:34:34 +0800 > > > Eryu Guan <[email protected]> wrote: > > > > > > > Hi, > > > > > > > > I'm using qemu 4.0 and hit segfault when tearing down kata sandbox, I > > > > think it's because io completion hits use-after-free when device is > > > > already gone. Is this a known bug that has been fixed? (I went through > > > > the git log but didn't find anything obvious). > > > > > > > > gdb backtrace is: > > > > > > > > Core was generated by `/usr/local/libexec/qemu-kvm -name > > > > sandbox-5b8df8c6c6901c3c0a9b02879be10fe8d69d6'. > > > > Program terminated with signal 11, Segmentation fault. > > > > #0 object_get_class (obj=obj@entry=0x0) at > > > > /usr/src/debug/qemu-4.0/qom/object.c:903 > > > > 903 return obj->class; > > > > (gdb) bt > > > > #0 object_get_class (obj=obj@entry=0x0) at > > > > /usr/src/debug/qemu-4.0/qom/object.c:903 > > > > #1 0x0000558a2c009e9b in virtio_notify_vector (vdev=0x558a2e7751d0, > > > > vector=<optimized out>) at > > > > /usr/src/debug/qemu-4.0/hw/virtio/virtio.c:1118 > > > > #2 0x0000558a2bfdcb1e in virtio_blk_discard_write_zeroes_complete ( > > > > opaque=0x558a2f2fd420, ret=0) > > > > at /usr/src/debug/qemu-4.0/hw/block/virtio-blk.c:186 > > > > #3 0x0000558a2c261c7e in blk_aio_complete (acb=0x558a2eed7420) > > > > at /usr/src/debug/qemu-4.0/block/block-backend.c:1305 > > > > #4 0x0000558a2c3031db in coroutine_trampoline (i0=<optimized out>, > > > > i1=<optimized out>) at > > > > /usr/src/debug/qemu-4.0/util/coroutine-ucontext.c:116 > > > > #5 0x00007f45b2f8b080 in ?? () from /lib64/libc.so.6 > > > > #6 0x00007fff9ed75780 in ?? () > > > > #7 0x0000000000000000 in ?? () > > > > > > > > It seems like qemu was completing a discard/write_zero request, but > > > > parent BusState was already freed & set to NULL. > > > > > > > > Do we need to drain all pending request before unrealizing virtio-blk > > > > device? Like the following patch proposed? > > > > > > > > https://lists.gnu.org/archive/html/qemu-devel/2017-06/msg02945.html > > > > > > > > If more info is needed, please let me know. > > > > > > may be this will help: https://patchwork.kernel.org/patch/11213047/ > > > > Yeah, this looks promising! I'll try it out (though it's a one-time > > crash for me). Thanks! > > After applying this patch, I don't see the original segfaut and > backtrace, but I see this crash > > [Thread debugging using libthread_db enabled] > Using host libthread_db library "/lib64/libthread_db.so.1". > Core was generated by `/usr/local/libexec/qemu-kvm -name > sandbox-a2f34a11a7e1449496503bbc4050ae040c0d3'. > Program terminated with signal 11, Segmentation fault. > #0 0x0000561216a57609 in virtio_pci_notify_write (opaque=0x5612184747e0, > addr=0, val=<optimized out>, size=<optimized out>) at > /usr/src/debug/qemu-4.0/hw/virtio/virtio-pci.c:1324 > 1324 VirtIOPCIProxy *proxy = > VIRTIO_PCI(DEVICE(vdev)->parent_bus->parent); > Missing separate debuginfos, use: debuginfo-install > glib2-2.42.2-5.1.alios7.x86_64 glibc-2.17-260.alios7.x86_64 > libgcc-4.8.5-28.alios7.1.x86_64 libseccomp-2.3.1-3.alios7.x86_64 > libstdc++-4.8.5-28.alios7.1.x86_64 numactl-libs-2.0.9-5.1.alios7.x86_64 > pixman-0.32.6-3.1.alios7.x86_64 zlib-1.2.7-16.2.alios7.x86_64 > (gdb) bt > #0 0x0000561216a57609 in virtio_pci_notify_write (opaque=0x5612184747e0, > addr=0, val=<optimized out>, size=<optimized out>) at > /usr/src/debug/qemu-4.0/hw/virtio/virtio-pci.c:1324 > #1 0x0000561216835b22 in memory_region_write_accessor (mr=<optimized out>, > addr=<optimized out>, value=<optimized out>, size=<optimized out>, > shift=<optimized out>, mask=<optimized out>, attrs=...) at > /usr/src/debug/qemu-4.0/memory.c:502 > #2 0x0000561216833c5d in access_with_adjusted_size (addr=addr@entry=0, > value=value@entry=0x7fcdeab1b8a8, size=size@entry=2, > access_size_min=<optimized out>, access_size_max=<optimized out>, > access_fn=0x561216835ac0 <memory_region_write_accessor>, mr=0x56121846d340, > attrs=...) > at /usr/src/debug/qemu-4.0/memory.c:568 > #3 0x0000561216837c66 in memory_region_dispatch_write > (mr=mr@entry=0x56121846d340, addr=0, data=<optimized out>, size=2, > attrs=attrs@entry=...) at /usr/src/debug/qemu-4.0/memory.c:1503 > #4 0x00005612167e036f in flatview_write_continue > (fv=fv@entry=0x56121852edd0, addr=addr@entry=841813602304, attrs=..., > buf=buf@entry=0x7fce7dd97028 <Address 0x7fce7dd97028 out of bounds>, > len=len@entry=2, addr1=<optimized out>, l=<optimized out>, mr=0x56121846d340) > at /usr/src/debug/qemu-4.0/exec.c:3279 > #5 0x00005612167e0506 in flatview_write (fv=0x56121852edd0, > addr=841813602304, attrs=..., buf=0x7fce7dd97028 <Address 0x7fce7dd97028 out > of bounds>, len=2) at /usr/src/debug/qemu-4.0/exec.c:3318 > #6 0x00005612167e4a1b in address_space_write (as=<optimized out>, > addr=<optimized out>, attrs=..., buf=<optimized out>, len=<optimized out>) at > /usr/src/debug/qemu-4.0/exec.c:3408 > #7 0x00005612167e4aa5 in address_space_rw (as=<optimized out>, > addr=<optimized out>, attrs=..., attrs@entry=..., > buf=buf@entry=0x7fce7dd97028 <Address 0x7fce7dd97028 out of bounds>, > len=<optimized out>, is_write=<optimized out>) at > /usr/src/debug/qemu-4.0/exec.c:3419 > #8 0x0000561216849da1 in kvm_cpu_exec (cpu=cpu@entry=0x56121849aa00) at > /usr/src/debug/qemu-4.0/accel/kvm/kvm-all.c:2034 > #9 0x000056121682255e in qemu_kvm_cpu_thread_fn > (arg=arg@entry=0x56121849aa00) at /usr/src/debug/qemu-4.0/cpus.c:1281 > #10 0x0000561216b794d6 in qemu_thread_start (args=<optimized out>) at > /usr/src/debug/qemu-4.0/util/qemu-thread-posix.c:502 > #11 0x00007fce7bef6e25 in start_thread () from /lib64/libpthread.so.0 > #12 0x00007fce7bc1ef1d in clone () from /lib64/libc.so.6 > > And I searched and found > https://bugzilla.redhat.com/show_bug.cgi?id=1706759 , which has the same > backtrace as above, and it seems commit 7bfde688fb1b ("virtio-blk: Add > blk_drain() to virtio_blk_device_unrealize()") is to fix this particular > bug. > > But I can still hit the bug even after applying the commit. Do I miss > anything?
Hi Eryu, This backtrace seems to be caused by this bug (there were two bugs in 1706759): https://bugzilla.redhat.com/show_bug.cgi?id=1708480 Although the solution hasn't been tested on virtio-blk yet, you may want to apply this patch: https://lists.nongnu.org/archive/html/qemu-devel/2019-12/msg05197.html Let me know if this works. Best regards, Julia Suvorova.
