On Thu, May 24, 2018 at 05:30:45PM +0300, Michael S. Tsirkin wrote: > On Thu, May 24, 2018 at 06:59:36PM +0800, Tiwei Bie wrote: > > On Thu, May 24, 2018 at 10:24:40AM +0800, Tiwei Bie wrote: > > > On Thu, May 24, 2018 at 07:21:01AM +0800, Tiwei Bie wrote: > > > > On Wed, May 23, 2018 at 06:43:29PM +0300, Michael S. Tsirkin wrote: > > > > > On Wed, May 23, 2018 at 06:36:05PM +0300, Michael S. Tsirkin wrote: > > > > > > On Wed, May 23, 2018 at 04:44:51PM +0300, Michael S. Tsirkin wrote: > > > > > > > On Thu, Apr 12, 2018 at 11:12:28PM +0800, Tiwei Bie wrote: > > > > > > > > When multi queue is enabled e.g. for a virtio-net device, > > > > > > > > each queue pair will have a vhost_dev, and the only thing > > > > > > > > shared between vhost devs currently is the chardev. This > > > > > > > > patch introduces a vhost-user state structure which will > > > > > > > > be shared by all vhost devs of the same virtio device. > > > > > > > > > > > > > > > > Signed-off-by: Tiwei Bie <tiwei....@intel.com> > > > > > > > > > > > > > > Unfortunately this patch seems to cause crashes. > > > > > > > To reproduce, simply run > > > > > > > make check-qtest-x86_64 > > > > > > > > > > > > > > Sorry that it took me a while to find - it triggers 90% of runs > > > > > > > but not > > > > > > > 100% which complicates bisection somewhat. > > > > > > > > It's my fault to not notice this bug before. > > > > I'm very sorry. Thank you so much for finding > > > > the root cause! > > > > > > > > > > > > > > > > > > > --- > > > > > > > > backends/cryptodev-vhost-user.c | 20 ++++++++++++++++++- > > > > > > > > hw/block/vhost-user-blk.c | 22 +++++++++++++++++++- > > > > > > > > hw/scsi/vhost-user-scsi.c | 20 ++++++++++++++++++- > > > > > > > > hw/virtio/Makefile.objs | 2 +- > > > > > > > > hw/virtio/vhost-stub.c | 10 ++++++++++ > > > > > > > > hw/virtio/vhost-user.c | 31 > > > > > > > > +++++++++++++++++++--------- > > > > > > > > include/hw/virtio/vhost-user-blk.h | 2 ++ > > > > > > > > include/hw/virtio/vhost-user-scsi.h | 2 ++ > > > > > > > > include/hw/virtio/vhost-user.h | 20 +++++++++++++++++++ > > > > > > > > net/vhost-user.c | 40 > > > > > > > > ++++++++++++++++++++++++++++++------- > > > > > > > > 10 files changed, 149 insertions(+), 20 deletions(-) > > > > > > > > create mode 100644 include/hw/virtio/vhost-user.h > > > > [...] > > > > > > > > qemu_chr_fe_set_handlers(&s->chr, NULL, NULL, > > > > > > > > net_vhost_user_event, NULL, > > > > > > > > nc0->name, NULL, > > > > > > > > @@ -319,6 +336,15 @@ static int > > > > > > > > net_vhost_user_init(NetClientState *peer, const char *device, > > > > > > > > assert(s->vhost_net); > > > > > > > > > > > > > > > > return 0; > > > > > > > > + > > > > > > > > +err: > > > > > > > > + if (user) { > > > > > > > > + vhost_user_cleanup(user); > > > > > > > > + g_free(user); > > > > > > > > + s->vhost_user = NULL; > > > > > > > > + } > > > > > > > > + > > > > > > > > + return -1; > > > > > > > > } > > > > > > > > > > > > > > > > static Chardev *net_vhost_claim_chardev( > > > > > > > > -- > > > > > > > > 2.11.0 > > > > > > > > > > > > So far I figured out that commenting the free of > > > > > > the structure removes the crash, so we seem to > > > > > > be dealing with a use-after free here. > > > > > > I suspect that in a MQ situation, one queue gets > > > > > > closed and attempts to free the structure > > > > > > while others still use it. > > > > > > > > > > > > diff --git a/net/vhost-user.c b/net/vhost-user.c > > > > > > index 525a061..6a1573b 100644 > > > > > > --- a/net/vhost-user.c > > > > > > +++ b/net/vhost-user.c > > > > > > @@ -157,8 +157,8 @@ static void > > > > > > net_vhost_user_cleanup(NetClientState *nc) > > > > > > s->vhost_net = NULL; > > > > > > } > > > > > > if (s->vhost_user) { > > > > > > - vhost_user_cleanup(s->vhost_user); > > > > > > - g_free(s->vhost_user); > > > > > > + //vhost_user_cleanup(s->vhost_user); > > > > > > + //g_free(s->vhost_user); > > > > > > s->vhost_user = NULL; > > > > > > } > > > > > > if (nc->queue_index == 0) { > > > > > > @@ -339,8 +339,8 @@ static int net_vhost_user_init(NetClientState > > > > > > *peer, const char *device, > > > > > > > > > > > > err: > > > > > > if (user) { > > > > > > - vhost_user_cleanup(user); > > > > > > - g_free(user); > > > > > > + //vhost_user_cleanup(user); > > > > > > + //g_free(user); > > > > > > s->vhost_user = NULL; > > > > > > } > > > > > > > > > > > > > > > > > > > > > So the following at least gets rid of the crashes. > > > > > I am not sure it does not leak memory though, > > > > > and not sure there aren't any configurations where > > > > > the 1st queue gets cleaned up first. > > > > > > > > > > Thoughts? > > > > > > > > Thank you so much for catching it and fixing > > > > it! I'll keep your SoB there. Thank you so > > > > much! I do appreciate it! > > > > > > > > You are right. This structure is freed multiple > > > > times when multi-queue is enabled. > > > > > > After a deeper digging, I got your point now.. > > > It could be a use-after-free instead of a double > > > free.. As it's safe to deinit the char which is > > > shared by all queue pairs when cleanup the 1st > > > queue pair, it should be safe to free vhost-user > > > structure there too. > > > > One thing worried me is that, I can't reproduce > > the crash with `make check-qtest-x86_64`. > > I sent a patch that will make test fail on qemu coredump.
That would be very useful! Without your explanation, I guess I won't be able to notice such crash in this test. Best regards, Tiwei Bie > > > I tried > > to run it a lot of times, but the only output I > > got each time was: > > > > CHK version_gen.h > > GTESTER check-qtest-x86_64 > > > > I did a quick glance of the `check-qtest-x86_64` > > target in the makefile, it seems that the relevant > > test is `tests/vhost-user-test`. So I also tried > > to run this test directly: > > > > make tests/vhost-user-test > > while true; do > > QTEST_QEMU_BINARY=x86_64-softmmu/qemu-system-x86_64 > > ./tests/vhost-user-test > > done > > > > And the only output in each loop I got was: > > > > /x86_64/vhost-user/migrate: OK > > /x86_64/vhost-user/multiqueue: OK > > /x86_64/vhost-user/read-guest-mem/memfd: OK > > /x86_64/vhost-user/read-guest-mem/memfile: OK > > > > So I'm still not quite sure what caused the crash > > on your side. But it does make more sense to free > > the vhost-user structure only when cleanup the > > 1st queue pair (i.e. where the `chr` is deinit-ed). > > > > I have sent a new patch set with above change: > > > > http://lists.gnu.org/archive/html/qemu-devel/2018-05/msg05508.html > > https://patchwork.kernel.org/bundle/btw/vhost-user-host-notifiers/ > > > > Because the above change is got from your diff > > and also based on your analysis, I kept your SoB > > in that patch (if you have any concern about it, > > please let me know). > > > > In this patch set, I also introduced a protocol > > feature to allow slave to send fds to master via > > the slave channel. > > > > If you still see crashes with the new patch set, > > please provide me a bit more details, e.g. the > > crash message. Thanks a lot! > > > > Best regards, > > Tiwei Bie --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org