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A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. For example, a program that has /dev/vdb open can call ioctl(HDIO_GETGEO) after hot unplug to invoke virtblk_getgeo(). Introduce a reference count in struct virtio_blk so that its lifetime covers both virtio_driver probe/remove and block_device_operations open/release users. This ensures that block_device_operations functions like virtblk_getgeo() can safely access struct virtio_blk. Add remove_mutex to pr...

A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. For example, a program that has /dev/vdb open can call ioctl(HDIO_GETGEO) after hot unplug to invoke virtblk_getgeo(). Introduce a reference count in struct virtio_blk so that its lifetime covers both virtio_driver probe/remove and block_device_operations open/release users. This ensures that block_device_operations functions like virtblk_getgeo() can safely access struct virtio_blk. Add remove_mutex to pr...

A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. This leads to a use-after-free accessing vblk->vdev in virtblk_getgeo() when ioctl(HDIO_GETGEO) is invoked: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] PGD 800000003a92f067 PUD 3a930067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 1310 Comm: hdio...

A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. This leads to a use-after-free accessing vblk->vdev in virtblk_getgeo() when ioctl(HDIO_GETGEO) is invoked: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] PGD 800000003a92f067 PUD 3a930067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 1310 Comm: hdio...

...+0100, Stefan Hajnoczi wrote: > > A userspace process holding a file descriptor to a virtio_blk device can > > still invoke block_device_operations after hot unplug. For example, a > > program that has /dev/vdb open can call ioctl(HDIO_GETGEO) after hot > > unplug to invoke virtblk_getgeo(). > > > which causes what? a use after free? Yes, use after free. I will include the kernel panic in the next revision. virtio_check_driver_offered_feature() accesses vdev->dev.driver, which doesn't work after virtblk_remove() has freed vdev :). > > > > Introd...

A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. This leads to a use-after-free accessing vblk->vdev in virtblk_getgeo() when ioctl(HDIO_GETGEO) is invoked: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] PGD 800000003a92f067 PUD 3a930067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 1310 Comm: hdio...

A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. This leads to a use-after-free accessing vblk->vdev in virtblk_getgeo() when ioctl(HDIO_GETGEO) is invoked: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] PGD 800000003a92f067 PUD 3a930067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 1310 Comm: hdio...

...2020 at 03:30:09PM +0100, Stefan Hajnoczi wrote: > A userspace process holding a file descriptor to a virtio_blk device can > still invoke block_device_operations after hot unplug. For example, a > program that has /dev/vdb open can call ioctl(HDIO_GETGEO) after hot > unplug to invoke virtblk_getgeo(). which causes what? a use after free? > > Introduce a reference count in struct virtio_blk so that its lifetime > covers both virtio_driver probe/remove and block_device_operations > open/release users. This ensures that block_device_operations functions > like virtblk_getg...

On Wed, Apr 29, 2020 at 05:53:45PM +0100, Stefan Hajnoczi wrote: > A userspace process holding a file descriptor to a virtio_blk device can > still invoke block_device_operations after hot unplug. This leads to a > use-after-free accessing vblk->vdev in virtblk_getgeo() when > ioctl(HDIO_GETGEO) is invoked: > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 > IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] > PGD 800000003a92f067 PUD 3a930067 PMD 0 > Oops: 0000 [#1] SMP...

...m: Stefan Hajnoczi <stefanha at redhat.com> [ Upstream commit 90b5feb8c4bebc76c27fcaf3e1a0e5ca2d319e9e ] A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. This leads to a use-after-free accessing vblk->vdev in virtblk_getgeo() when ioctl(HDIO_GETGEO) is invoked: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] PGD 800000003a92f067 PUD 3a930067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 1310 Comm: hdio...

...m: Stefan Hajnoczi <stefanha at redhat.com> [ Upstream commit 90b5feb8c4bebc76c27fcaf3e1a0e5ca2d319e9e ] A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. This leads to a use-after-free accessing vblk->vdev in virtblk_getgeo() when ioctl(HDIO_GETGEO) is invoked: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] PGD 800000003a92f067 PUD 3a930067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 1310 Comm: hdio...

...m: Stefan Hajnoczi <stefanha at redhat.com> [ Upstream commit 90b5feb8c4bebc76c27fcaf3e1a0e5ca2d319e9e ] A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. This leads to a use-after-free accessing vblk->vdev in virtblk_getgeo() when ioctl(HDIO_GETGEO) is invoked: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] PGD 800000003a92f067 PUD 3a930067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 1310 Comm: hdio...

...m: Stefan Hajnoczi <stefanha at redhat.com> [ Upstream commit 90b5feb8c4bebc76c27fcaf3e1a0e5ca2d319e9e ] A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. This leads to a use-after-free accessing vblk->vdev in virtblk_getgeo() when ioctl(HDIO_GETGEO) is invoked: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] PGD 800000003a92f067 PUD 3a930067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 1310 Comm: hdio...

On Thu, 30 Apr 2020 15:04:42 +0100 Stefan Hajnoczi <stefanha at redhat.com> wrote: > A userspace process holding a file descriptor to a virtio_blk device can > still invoke block_device_operations after hot unplug. This leads to a > use-after-free accessing vblk->vdev in virtblk_getgeo() when > ioctl(HDIO_GETGEO) is invoked: > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 > IP: [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] > PGD 800000003a92f067 PUD 3a930067 PMD 0 > Oops: 0000 [#1] SMP...