| Message ID | 20220221114916.107045-1-sgarzare@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | vhost/vsock: don't check owner in vhost_vsock_stop() while releasing | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On Mon, Feb 21, 2022 at 12:49 PM Stefano Garzarella <sgarzare@redhat.com> wrote: > > vhost_vsock_stop() calls vhost_dev_check_owner() to check the device > ownership. It expects current->mm to be valid. > > vhost_vsock_stop() is also called by vhost_vsock_dev_release() when > the user has not done close(), so when we are in do_exit(). In this > case current->mm is invalid and we're releasing the device, so we > should clean it anyway. > > Let's check the owner only when vhost_vsock_stop() is called > by an ioctl. > > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") > Cc: stable@vger.kernel.org > Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> > --- > drivers/vhost/vsock.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) Reported-and-tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+3140b17cb44a7b174008@syzkaller.appspotmail.com
On Mon, Feb 21, 2022 at 12:49:16PM +0100, Stefano Garzarella wrote: > vhost_vsock_stop() calls vhost_dev_check_owner() to check the device > ownership. It expects current->mm to be valid. > > vhost_vsock_stop() is also called by vhost_vsock_dev_release() when > the user has not done close(), so when we are in do_exit(). In this > case current->mm is invalid and we're releasing the device, so we > should clean it anyway. > > Let's check the owner only when vhost_vsock_stop() is called > by an ioctl. > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") > Cc: stable@vger.kernel.org > Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> > --- > drivers/vhost/vsock.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c > index d6ca1c7ad513..f00d2dfd72b7 100644 > --- a/drivers/vhost/vsock.c > +++ b/drivers/vhost/vsock.c > @@ -629,16 +629,18 @@ static int vhost_vsock_start(struct vhost_vsock *vsock) > return ret; > } > > -static int vhost_vsock_stop(struct vhost_vsock *vsock) > +static int vhost_vsock_stop(struct vhost_vsock *vsock, bool check_owner) > { > size_t i; > int ret; > > mutex_lock(&vsock->dev.mutex); > > - ret = vhost_dev_check_owner(&vsock->dev); > - if (ret) > - goto err; > + if (check_owner) { > + ret = vhost_dev_check_owner(&vsock->dev); > + if (ret) > + goto err; > + } > > for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) { > struct vhost_virtqueue *vq = &vsock->vqs[i]; > @@ -753,7 +755,7 @@ static int vhost_vsock_dev_release(struct inode *inode, struct file *file) > * inefficient. Room for improvement here. */ > vsock_for_each_connected_socket(vhost_vsock_reset_orphans); > > - vhost_vsock_stop(vsock); Let's add an explanation: When invoked from release we can not fail so we don't check return code of vhost_vsock_stop. We need to stop vsock even if it's not the owner. > + vhost_vsock_stop(vsock, false); > vhost_vsock_flush(vsock); > vhost_dev_stop(&vsock->dev); > > @@ -868,7 +870,7 @@ static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl, > if (start) > return vhost_vsock_start(vsock); > else > - return vhost_vsock_stop(vsock); > + return vhost_vsock_stop(vsock, true); > case VHOST_GET_FEATURES: > features = VHOST_VSOCK_FEATURES; > if (copy_to_user(argp, &features, sizeof(features))) > -- > 2.35.1
On Mon, Feb 21, 2022 at 10:03:39AM -0500, Michael S. Tsirkin wrote: >On Mon, Feb 21, 2022 at 12:49:16PM +0100, Stefano Garzarella wrote: >> vhost_vsock_stop() calls vhost_dev_check_owner() to check the device >> ownership. It expects current->mm to be valid. >> >> vhost_vsock_stop() is also called by vhost_vsock_dev_release() when >> the user has not done close(), so when we are in do_exit(). In this >> case current->mm is invalid and we're releasing the device, so we >> should clean it anyway. >> >> Let's check the owner only when vhost_vsock_stop() is called >> by an ioctl. > > > > >> Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") >> Cc: stable@vger.kernel.org >> Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com >> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> >> --- >> drivers/vhost/vsock.c | 14 ++++++++------ >> 1 file changed, 8 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c >> index d6ca1c7ad513..f00d2dfd72b7 100644 >> --- a/drivers/vhost/vsock.c >> +++ b/drivers/vhost/vsock.c >> @@ -629,16 +629,18 @@ static int vhost_vsock_start(struct vhost_vsock *vsock) >> return ret; >> } >> >> -static int vhost_vsock_stop(struct vhost_vsock *vsock) >> +static int vhost_vsock_stop(struct vhost_vsock *vsock, bool check_owner) > >> { >> size_t i; >> int ret; >> >> mutex_lock(&vsock->dev.mutex); >> >> - ret = vhost_dev_check_owner(&vsock->dev); >> - if (ret) >> - goto err; >> + if (check_owner) { >> + ret = vhost_dev_check_owner(&vsock->dev); >> + if (ret) >> + goto err; >> + } >> >> for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) { >> struct vhost_virtqueue *vq = &vsock->vqs[i]; >> @@ -753,7 +755,7 @@ static int vhost_vsock_dev_release(struct inode *inode, struct file *file) >> * inefficient. Room for improvement here. */ >> vsock_for_each_connected_socket(vhost_vsock_reset_orphans); >> >> - vhost_vsock_stop(vsock); > >Let's add an explanation: > >When invoked from release we can not fail so we don't >check return code of vhost_vsock_stop. >We need to stop vsock even if it's not the owner. Do you want me to send a v2 by adding this as a comment in the code? Thanks, Stefano
On Mon, Feb 21, 2022 at 02:59:30PM +0100, Stefano Garzarella wrote: > On Mon, Feb 21, 2022 at 12:49 PM Stefano Garzarella <sgarzare@redhat.com> wrote: > > > > vhost_vsock_stop() calls vhost_dev_check_owner() to check the device > > ownership. It expects current->mm to be valid. > > > > vhost_vsock_stop() is also called by vhost_vsock_dev_release() when > > the user has not done close(), so when we are in do_exit(). In this > > case current->mm is invalid and we're releasing the device, so we > > should clean it anyway. > > > > Let's check the owner only when vhost_vsock_stop() is called > > by an ioctl. > > > > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") > > Cc: stable@vger.kernel.org > > Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> > > --- > > drivers/vhost/vsock.c | 14 ++++++++------ > > 1 file changed, 8 insertions(+), 6 deletions(-) > > Reported-and-tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com I don't think this patch fixes "INFO: task hung in vhost_work_dev_flush" even though syzbot says so. I am able to reproduce the issue locally even with this patch applied. Thanks, - Anirudh. > Reported-and-tested-by: syzbot+3140b17cb44a7b174008@syzkaller.appspotmail.com >
On Mon, Feb 21, 2022 at 09:44:39PM +0530, Anirudh Rayabharam wrote: >On Mon, Feb 21, 2022 at 02:59:30PM +0100, Stefano Garzarella wrote: >> On Mon, Feb 21, 2022 at 12:49 PM Stefano Garzarella <sgarzare@redhat.com> wrote: >> > >> > vhost_vsock_stop() calls vhost_dev_check_owner() to check the device >> > ownership. It expects current->mm to be valid. >> > >> > vhost_vsock_stop() is also called by vhost_vsock_dev_release() when >> > the user has not done close(), so when we are in do_exit(). In this >> > case current->mm is invalid and we're releasing the device, so we >> > should clean it anyway. >> > >> > Let's check the owner only when vhost_vsock_stop() is called >> > by an ioctl. >> > >> > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") >> > Cc: stable@vger.kernel.org >> > Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com >> > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> >> > --- >> > drivers/vhost/vsock.c | 14 ++++++++------ >> > 1 file changed, 8 insertions(+), 6 deletions(-) >> >> Reported-and-tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com > >I don't think this patch fixes "INFO: task hung in vhost_work_dev_flush" >even though syzbot says so. I am able to reproduce the issue locally >even with this patch applied. Are you using the sysbot reproducer or another test? In that case, can you share it? From the stack trace it seemed to me that the worker accesses a zone that has been cleaned (iotlb), so it is invalid and fails. That's why I had this patch tested which should stop the worker before cleaning. Thanks, Stefano
On Mon, Feb 21, 2022 at 05:44:20PM +0100, Stefano Garzarella wrote: > On Mon, Feb 21, 2022 at 09:44:39PM +0530, Anirudh Rayabharam wrote: > > On Mon, Feb 21, 2022 at 02:59:30PM +0100, Stefano Garzarella wrote: > > > On Mon, Feb 21, 2022 at 12:49 PM Stefano Garzarella <sgarzare@redhat.com> wrote: > > > > > > > > vhost_vsock_stop() calls vhost_dev_check_owner() to check the device > > > > ownership. It expects current->mm to be valid. > > > > > > > > vhost_vsock_stop() is also called by vhost_vsock_dev_release() when > > > > the user has not done close(), so when we are in do_exit(). In this > > > > case current->mm is invalid and we're releasing the device, so we > > > > should clean it anyway. > > > > > > > > Let's check the owner only when vhost_vsock_stop() is called > > > > by an ioctl. > > > > > > > > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") > > > > Cc: stable@vger.kernel.org > > > > Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com > > > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> > > > > --- > > > > drivers/vhost/vsock.c | 14 ++++++++------ > > > > 1 file changed, 8 insertions(+), 6 deletions(-) > > > > > > Reported-and-tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com > > > > I don't think this patch fixes "INFO: task hung in vhost_work_dev_flush" > > even though syzbot says so. I am able to reproduce the issue locally > > even with this patch applied. > > Are you using the sysbot reproducer or another test? > In that case, can you share it? I am using the syzbot reproducer. > > From the stack trace it seemed to me that the worker accesses a zone that > has been cleaned (iotlb), so it is invalid and fails. Would the thread hang in that case? How? Thanks, - Anirudh. > That's why I had this patch tested which should stop the worker before > cleaning. > > Thanks, > Stefano >
On Mon, Feb 21, 2022 at 11:33:11PM +0530, Anirudh Rayabharam wrote: >On Mon, Feb 21, 2022 at 05:44:20PM +0100, Stefano Garzarella wrote: >> On Mon, Feb 21, 2022 at 09:44:39PM +0530, Anirudh Rayabharam wrote: >> > On Mon, Feb 21, 2022 at 02:59:30PM +0100, Stefano Garzarella wrote: >> > > On Mon, Feb 21, 2022 at 12:49 PM Stefano Garzarella <sgarzare@redhat.com> wrote: >> > > > >> > > > vhost_vsock_stop() calls vhost_dev_check_owner() to check the device >> > > > ownership. It expects current->mm to be valid. >> > > > >> > > > vhost_vsock_stop() is also called by vhost_vsock_dev_release() when >> > > > the user has not done close(), so when we are in do_exit(). In this >> > > > case current->mm is invalid and we're releasing the device, so we >> > > > should clean it anyway. >> > > > >> > > > Let's check the owner only when vhost_vsock_stop() is called >> > > > by an ioctl. >> > > > >> > > > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") >> > > > Cc: stable@vger.kernel.org >> > > > Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com >> > > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> >> > > > --- >> > > > drivers/vhost/vsock.c | 14 ++++++++------ >> > > > 1 file changed, 8 insertions(+), 6 deletions(-) >> > > >> > > Reported-and-tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com >> > >> > I don't think this patch fixes "INFO: task hung in vhost_work_dev_flush" >> > even though syzbot says so. I am able to reproduce the issue locally >> > even with this patch applied. >> >> Are you using the sysbot reproducer or another test? >> In that case, can you share it? > >I am using the syzbot reproducer. > >> >> From the stack trace it seemed to me that the worker accesses a zone that >> has been cleaned (iotlb), so it is invalid and fails. > >Would the thread hang in that case? How? Looking at this log [1] it seems that the process is blocked on the wait_for_completion() in vhost_work_dev_flush(). Since we're not setting the backend to NULL to stop the worker, it's likely that the worker will keep running, preventing the flush work from completing. [1] https://syzkaller.appspot.com/text?tag=CrashLog&x=153f0852700000
On Mon, Feb 21, 2022 at 07:26:28PM +0100, Stefano Garzarella wrote: > On Mon, Feb 21, 2022 at 11:33:11PM +0530, Anirudh Rayabharam wrote: > > On Mon, Feb 21, 2022 at 05:44:20PM +0100, Stefano Garzarella wrote: > > > On Mon, Feb 21, 2022 at 09:44:39PM +0530, Anirudh Rayabharam wrote: > > > > On Mon, Feb 21, 2022 at 02:59:30PM +0100, Stefano Garzarella wrote: > > > > > On Mon, Feb 21, 2022 at 12:49 PM Stefano Garzarella <sgarzare@redhat.com> wrote: > > > > > > > > > > > > vhost_vsock_stop() calls vhost_dev_check_owner() to check the device > > > > > > ownership. It expects current->mm to be valid. > > > > > > > > > > > > vhost_vsock_stop() is also called by vhost_vsock_dev_release() when > > > > > > the user has not done close(), so when we are in do_exit(). In this > > > > > > case current->mm is invalid and we're releasing the device, so we > > > > > > should clean it anyway. > > > > > > > > > > > > Let's check the owner only when vhost_vsock_stop() is called > > > > > > by an ioctl. > > > > > > > > > > > > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") > > > > > > Cc: stable@vger.kernel.org > > > > > > Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com > > > > > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> > > > > > > --- > > > > > > drivers/vhost/vsock.c | 14 ++++++++------ > > > > > > 1 file changed, 8 insertions(+), 6 deletions(-) > > > > > > > > > > Reported-and-tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com > > > > > > > > I don't think this patch fixes "INFO: task hung in vhost_work_dev_flush" > > > > even though syzbot says so. I am able to reproduce the issue locally > > > > even with this patch applied. > > > > > > Are you using the sysbot reproducer or another test? > > > In that case, can you share it? > > > > I am using the syzbot reproducer. > > > > > > > > From the stack trace it seemed to me that the worker accesses a zone that > > > has been cleaned (iotlb), so it is invalid and fails. > > > > Would the thread hang in that case? How? > > Looking at this log [1] it seems that the process is blocked on the > wait_for_completion() in vhost_work_dev_flush(). > > Since we're not setting the backend to NULL to stop the worker, it's likely > that the worker will keep running, preventing the flush work from > completing. The log shows that the worker thread is stuck in iotlb_access_ok(). How will setting the backend to NULL stop it? During my debugging I found that the worker is stuck in this while loop: 1361 while (len > s) { 1362 map = vhost_iotlb_itree_first(umem, addr, last); 1363 if (map == NULL || map->start > addr) { 1364 vhost_iotlb_miss(vq, addr, access); 1365 return false; 1366 } else if (!(map->perm & access)) { 1367 /* Report the possible access violation by 1368 * request another translation from userspace. 1369 */ 1370 return false; 1371 } 1372 1373 pr_info("iotlb_access_ok: after msize=%llu, mstart=%llu\n", 1374 map->size, map->start); 1375 size = map->size - addr + map->start; 1376 1377 if (orig_addr == addr && size >= len) 1378 vhost_vq_meta_update(vq, map, type); 1379 1380 s += size; 1381 addr += size; 1382 } > > [1] https://syzkaller.appspot.com/text?tag=CrashLog&x=153f0852700000 >
Hi Stefano,
url: https://github.com/0day-ci/linux/commits/Stefano-Garzarella/vhost-vsock-don-t-check-owner-in-vhost_vsock_stop-while-releasing/20220221-195038
base: https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git linux-next
config: x86_64-randconfig-m031-20220221 (https://download.01.org/0day-ci/archive/20220222/202202220707.AM3rKUcP-lkp@intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
smatch warnings:
drivers/vhost/vsock.c:655 vhost_vsock_stop() error: uninitialized symbol 'ret'.
vim +/ret +655 drivers/vhost/vsock.c
3ace84c91bfcde Stefano Garzarella 2022-02-21 632 static int vhost_vsock_stop(struct vhost_vsock *vsock, bool check_owner)
433fc58e6bf2c8 Asias He 2016-07-28 633 {
433fc58e6bf2c8 Asias He 2016-07-28 634 size_t i;
433fc58e6bf2c8 Asias He 2016-07-28 635 int ret;
433fc58e6bf2c8 Asias He 2016-07-28 636
433fc58e6bf2c8 Asias He 2016-07-28 637 mutex_lock(&vsock->dev.mutex);
433fc58e6bf2c8 Asias He 2016-07-28 638
3ace84c91bfcde Stefano Garzarella 2022-02-21 639 if (check_owner) {
433fc58e6bf2c8 Asias He 2016-07-28 640 ret = vhost_dev_check_owner(&vsock->dev);
433fc58e6bf2c8 Asias He 2016-07-28 641 if (ret)
433fc58e6bf2c8 Asias He 2016-07-28 642 goto err;
3ace84c91bfcde Stefano Garzarella 2022-02-21 643 }
"ret" not initialized on else path.
433fc58e6bf2c8 Asias He 2016-07-28 644
433fc58e6bf2c8 Asias He 2016-07-28 645 for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
433fc58e6bf2c8 Asias He 2016-07-28 646 struct vhost_virtqueue *vq = &vsock->vqs[i];
433fc58e6bf2c8 Asias He 2016-07-28 647
433fc58e6bf2c8 Asias He 2016-07-28 648 mutex_lock(&vq->mutex);
247643f85782fc Eugenio Pérez 2020-03-31 649 vhost_vq_set_backend(vq, NULL);
433fc58e6bf2c8 Asias He 2016-07-28 650 mutex_unlock(&vq->mutex);
433fc58e6bf2c8 Asias He 2016-07-28 651 }
433fc58e6bf2c8 Asias He 2016-07-28 652
433fc58e6bf2c8 Asias He 2016-07-28 653 err:
433fc58e6bf2c8 Asias He 2016-07-28 654 mutex_unlock(&vsock->dev.mutex);
433fc58e6bf2c8 Asias He 2016-07-28 @655 return ret;
433fc58e6bf2c8 Asias He 2016-07-28 656 }
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
On Tue, Feb 22, 2022 at 08:30:17AM +0300, Dan Carpenter wrote: >Hi Stefano, > >url: https://github.com/0day-ci/linux/commits/Stefano-Garzarella/vhost-vsock-don-t-check-owner-in-vhost_vsock_stop-while-releasing/20220221-195038 >base: https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git linux-next >config: x86_64-randconfig-m031-20220221 (https://download.01.org/0day-ci/archive/20220222/202202220707.AM3rKUcP-lkp@intel.com/config) >compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 > >If you fix the issue, kindly add following tag as appropriate >Reported-by: kernel test robot <lkp@intel.com> >Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > >smatch warnings: >drivers/vhost/vsock.c:655 vhost_vsock_stop() error: uninitialized symbol 'ret'. > >vim +/ret +655 drivers/vhost/vsock.c > >3ace84c91bfcde Stefano Garzarella 2022-02-21 632 static int vhost_vsock_stop(struct vhost_vsock *vsock, bool check_owner) >433fc58e6bf2c8 Asias He 2016-07-28 633 { >433fc58e6bf2c8 Asias He 2016-07-28 634 size_t i; >433fc58e6bf2c8 Asias He 2016-07-28 635 int ret; >433fc58e6bf2c8 Asias He 2016-07-28 636 >433fc58e6bf2c8 Asias He 2016-07-28 637 mutex_lock(&vsock->dev.mutex); >433fc58e6bf2c8 Asias He 2016-07-28 638 >3ace84c91bfcde Stefano Garzarella 2022-02-21 639 if (check_owner) { >433fc58e6bf2c8 Asias He 2016-07-28 640 ret = vhost_dev_check_owner(&vsock->dev); >433fc58e6bf2c8 Asias He 2016-07-28 641 if (ret) >433fc58e6bf2c8 Asias He 2016-07-28 642 goto err; >3ace84c91bfcde Stefano Garzarella 2022-02-21 643 } > >"ret" not initialized on else path. Oooops, I was testing with vhost_vsock_dev_release() where we don't check the ret value, but of course we need to initialize it to 0 for the vhost_vsock_dev_ioctl() use case. I'll fix in the v2. Thanks for the report, Stefano
On Tue, Feb 22, 2022 at 01:06:12AM +0530, Anirudh Rayabharam wrote: >On Mon, Feb 21, 2022 at 07:26:28PM +0100, Stefano Garzarella wrote: >> On Mon, Feb 21, 2022 at 11:33:11PM +0530, Anirudh Rayabharam wrote: >> > On Mon, Feb 21, 2022 at 05:44:20PM +0100, Stefano Garzarella wrote: >> > > On Mon, Feb 21, 2022 at 09:44:39PM +0530, Anirudh Rayabharam wrote: >> > > > On Mon, Feb 21, 2022 at 02:59:30PM +0100, Stefano Garzarella wrote: >> > > > > On Mon, Feb 21, 2022 at 12:49 PM Stefano Garzarella <sgarzare@redhat.com> wrote: >> > > > > > >> > > > > > vhost_vsock_stop() calls vhost_dev_check_owner() to check the device >> > > > > > ownership. It expects current->mm to be valid. >> > > > > > >> > > > > > vhost_vsock_stop() is also called by vhost_vsock_dev_release() when >> > > > > > the user has not done close(), so when we are in do_exit(). In this >> > > > > > case current->mm is invalid and we're releasing the device, so we >> > > > > > should clean it anyway. >> > > > > > >> > > > > > Let's check the owner only when vhost_vsock_stop() is called >> > > > > > by an ioctl. >> > > > > > >> > > > > > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") >> > > > > > Cc: stable@vger.kernel.org >> > > > > > Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com >> > > > > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> >> > > > > > --- >> > > > > > drivers/vhost/vsock.c | 14 ++++++++------ >> > > > > > 1 file changed, 8 insertions(+), 6 deletions(-) >> > > > > >> > > > > Reported-and-tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com >> > > > >> > > > I don't think this patch fixes "INFO: task hung in vhost_work_dev_flush" >> > > > even though syzbot says so. I am able to reproduce the issue locally >> > > > even with this patch applied. >> > > >> > > Are you using the sysbot reproducer or another test? >> > > In that case, can you share it? >> > >> > I am using the syzbot reproducer. >> > >> > > >> > > From the stack trace it seemed to me that the worker accesses a zone that >> > > has been cleaned (iotlb), so it is invalid and fails. >> > >> > Would the thread hang in that case? How? >> >> Looking at this log [1] it seems that the process is blocked on the >> wait_for_completion() in vhost_work_dev_flush(). >> >> Since we're not setting the backend to NULL to stop the worker, it's likely >> that the worker will keep running, preventing the flush work from >> completing. > >The log shows that the worker thread is stuck in iotlb_access_ok(). How >will setting the backend to NULL stop it? During my debugging I found >that the worker is stuck in this while loop: Okay, looking at your new patch, now I see. If we enter in this loop before setting the backend to NULL and we have start = 0 and end = (u64) -1 , we should be there forever. I'll remove that tag in v2, but the test might fail without this patch applied, because for now we don't stop workers correctly. Thanks, Stefano
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c index d6ca1c7ad513..f00d2dfd72b7 100644 --- a/drivers/vhost/vsock.c +++ b/drivers/vhost/vsock.c @@ -629,16 +629,18 @@ static int vhost_vsock_start(struct vhost_vsock *vsock) return ret; } -static int vhost_vsock_stop(struct vhost_vsock *vsock) +static int vhost_vsock_stop(struct vhost_vsock *vsock, bool check_owner) { size_t i; int ret; mutex_lock(&vsock->dev.mutex); - ret = vhost_dev_check_owner(&vsock->dev); - if (ret) - goto err; + if (check_owner) { + ret = vhost_dev_check_owner(&vsock->dev); + if (ret) + goto err; + } for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) { struct vhost_virtqueue *vq = &vsock->vqs[i]; @@ -753,7 +755,7 @@ static int vhost_vsock_dev_release(struct inode *inode, struct file *file) * inefficient. Room for improvement here. */ vsock_for_each_connected_socket(vhost_vsock_reset_orphans); - vhost_vsock_stop(vsock); + vhost_vsock_stop(vsock, false); vhost_vsock_flush(vsock); vhost_dev_stop(&vsock->dev); @@ -868,7 +870,7 @@ static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl, if (start) return vhost_vsock_start(vsock); else - return vhost_vsock_stop(vsock); + return vhost_vsock_stop(vsock, true); case VHOST_GET_FEATURES: features = VHOST_VSOCK_FEATURES; if (copy_to_user(argp, &features, sizeof(features)))
vhost_vsock_stop() calls vhost_dev_check_owner() to check the device ownership. It expects current->mm to be valid. vhost_vsock_stop() is also called by vhost_vsock_dev_release() when the user has not done close(), so when we are in do_exit(). In this case current->mm is invalid and we're releasing the device, so we should clean it anyway. Let's check the owner only when vhost_vsock_stop() is called by an ioctl. Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") Cc: stable@vger.kernel.org Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> --- drivers/vhost/vsock.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)