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! Eryu
