| Message ID | 20200430140442.171016-1-stefanha@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4] virtio-blk: handle block_device_operations callbacks after hot unplug | expand |
On Thu, Apr 30, 2020 at 03:04:42PM +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 > CPU: 0 PID: 1310 Comm: hdio-getgeo Tainted: G OE ------------ 3.10.0-1062.el7.x86_64 #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 > task: ffff9be5fbfb8000 ti: ffff9be5fa890000 task.ti: ffff9be5fa890000 > RIP: 0010:[<ffffffffc00e5450>] [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] > RSP: 0018:ffff9be5fa893dc8 EFLAGS: 00010246 > RAX: ffff9be5fc3f3400 RBX: ffff9be5fa893e30 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff9be5fbc10b40 > RBP: ffff9be5fa893dc8 R08: 0000000000000301 R09: 0000000000000301 > R10: 0000000000000000 R11: 0000000000000000 R12: ffff9be5fdc24680 > R13: ffff9be5fbc10b40 R14: ffff9be5fbc10480 R15: 0000000000000000 > FS: 00007f1bfb968740(0000) GS:ffff9be5ffc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000090 CR3: 000000003a894000 CR4: 0000000000360ff0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > [<ffffffffc016ac37>] virtblk_getgeo+0x47/0x110 [virtio_blk] > [<ffffffff8d3f200d>] ? handle_mm_fault+0x39d/0x9b0 > [<ffffffff8d561265>] blkdev_ioctl+0x1f5/0xa20 > [<ffffffff8d488771>] block_ioctl+0x41/0x50 > [<ffffffff8d45d9e0>] do_vfs_ioctl+0x3a0/0x5a0 > [<ffffffff8d45dc81>] SyS_ioctl+0xa1/0xc0 > > A related problem is that virtblk_remove() leaks the vd_index_ida index > when something still holds a reference to vblk->disk during hot unplug. > This causes virtio-blk device names to be lost (vda, vdb, etc). > > Fix these issues by protecting vblk->vdev with a mutex and reference > counting vblk so the vd_index_ida index can be removed in all cases. > > Fixes: 48e4043d4529523cbc7fa8dd745bd8e2c45ce1d3 > ("virtio: add virtio disk geometry feature") > Reported-by: Lance Digby <ldigby@redhat.com> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > v4: > * Clarify vdev_mutex usage [Stefano and Michael] > > drivers/block/virtio_blk.c | 86 ++++++++++++++++++++++++++++++++++---- > 1 file changed, 78 insertions(+), 8 deletions(-) Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Thanks, Stefano > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 93468b7c6701..9d21bf0f155e 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -33,6 +33,15 @@ struct virtio_blk_vq { > } ____cacheline_aligned_in_smp; > > struct virtio_blk { > + /* > + * This mutex must be held by anything that may run after > + * virtblk_remove() sets vblk->vdev to NULL. > + * > + * blk-mq, virtqueue processing, and sysfs attribute code paths are > + * shut down before vblk->vdev is set to NULL and therefore do not need > + * to hold this mutex. > + */ > + struct mutex vdev_mutex; > struct virtio_device *vdev; > > /* The disk structure for the kernel. */ > @@ -44,6 +53,13 @@ struct virtio_blk { > /* Process context for config space updates */ > struct work_struct config_work; > > + /* > + * Tracks references from block_device_operations open/release and > + * virtio_driver probe/remove so this object can be freed once no > + * longer in use. > + */ > + refcount_t refs; > + > /* What host tells us, plus 2 for header & tailer. */ > unsigned int sg_elems; > > @@ -295,10 +311,55 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str) > return err; > } > > +static void virtblk_get(struct virtio_blk *vblk) > +{ > + refcount_inc(&vblk->refs); > +} > + > +static void virtblk_put(struct virtio_blk *vblk) > +{ > + if (refcount_dec_and_test(&vblk->refs)) { > + ida_simple_remove(&vd_index_ida, vblk->index); > + mutex_destroy(&vblk->vdev_mutex); > + kfree(vblk); > + } > +} > + > +static int virtblk_open(struct block_device *bd, fmode_t mode) > +{ > + struct virtio_blk *vblk = bd->bd_disk->private_data; > + int ret = 0; > + > + mutex_lock(&vblk->vdev_mutex); > + > + if (vblk->vdev) > + virtblk_get(vblk); > + else > + ret = -ENXIO; > + > + mutex_unlock(&vblk->vdev_mutex); > + return ret; > +} > + > +static void virtblk_release(struct gendisk *disk, fmode_t mode) > +{ > + struct virtio_blk *vblk = disk->private_data; > + > + virtblk_put(vblk); > +} > + > /* We provide getgeo only to please some old bootloader/partitioning tools */ > static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo) > { > struct virtio_blk *vblk = bd->bd_disk->private_data; > + int ret = 0; > + > + mutex_lock(&vblk->vdev_mutex); > + > + if (!vblk->vdev) { > + ret = -ENXIO; > + goto out; > + } > > /* see if the host passed in geometry config */ > if (virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_GEOMETRY)) { > @@ -314,11 +375,15 @@ static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo) > geo->sectors = 1 << 5; > geo->cylinders = get_capacity(bd->bd_disk) >> 11; > } > - return 0; > +out: > + mutex_unlock(&vblk->vdev_mutex); > + return ret; > } > > static const struct block_device_operations virtblk_fops = { > .owner = THIS_MODULE, > + .open = virtblk_open, > + .release = virtblk_release, > .getgeo = virtblk_getgeo, > }; > > @@ -655,6 +720,10 @@ static int virtblk_probe(struct virtio_device *vdev) > goto out_free_index; > } > > + /* This reference is dropped in virtblk_remove(). */ > + refcount_set(&vblk->refs, 1); > + mutex_init(&vblk->vdev_mutex); > + > vblk->vdev = vdev; > vblk->sg_elems = sg_elems; > > @@ -820,8 +889,6 @@ static int virtblk_probe(struct virtio_device *vdev) > static void virtblk_remove(struct virtio_device *vdev) > { > struct virtio_blk *vblk = vdev->priv; > - int index = vblk->index; > - int refc; > > /* Make sure no work handler is accessing the device. */ > flush_work(&vblk->config_work); > @@ -831,18 +898,21 @@ static void virtblk_remove(struct virtio_device *vdev) > > blk_mq_free_tag_set(&vblk->tag_set); > > + mutex_lock(&vblk->vdev_mutex); > + > /* Stop all the virtqueues. */ > vdev->config->reset(vdev); > > - refc = kref_read(&disk_to_dev(vblk->disk)->kobj.kref); > + /* Virtqueues are stopped, nothing can use vblk->vdev anymore. */ > + vblk->vdev = NULL; > + > put_disk(vblk->disk); > vdev->config->del_vqs(vdev); > kfree(vblk->vqs); > - kfree(vblk); > > - /* Only free device id if we don't have any users */ > - if (refc == 1) > - ida_simple_remove(&vd_index_ida, index); > + mutex_unlock(&vblk->vdev_mutex); > + > + virtblk_put(vblk); > } > > #ifdef CONFIG_PM_SLEEP > -- > 2.25.3 >
On Thu, 30 Apr 2020 15:04:42 +0100 Stefan Hajnoczi <stefanha@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 > CPU: 0 PID: 1310 Comm: hdio-getgeo Tainted: G OE ------------ 3.10.0-1062.el7.x86_64 #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 > task: ffff9be5fbfb8000 ti: ffff9be5fa890000 task.ti: ffff9be5fa890000 > RIP: 0010:[<ffffffffc00e5450>] [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] > RSP: 0018:ffff9be5fa893dc8 EFLAGS: 00010246 > RAX: ffff9be5fc3f3400 RBX: ffff9be5fa893e30 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff9be5fbc10b40 > RBP: ffff9be5fa893dc8 R08: 0000000000000301 R09: 0000000000000301 > R10: 0000000000000000 R11: 0000000000000000 R12: ffff9be5fdc24680 > R13: ffff9be5fbc10b40 R14: ffff9be5fbc10480 R15: 0000000000000000 > FS: 00007f1bfb968740(0000) GS:ffff9be5ffc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000090 CR3: 000000003a894000 CR4: 0000000000360ff0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > [<ffffffffc016ac37>] virtblk_getgeo+0x47/0x110 [virtio_blk] > [<ffffffff8d3f200d>] ? handle_mm_fault+0x39d/0x9b0 > [<ffffffff8d561265>] blkdev_ioctl+0x1f5/0xa20 > [<ffffffff8d488771>] block_ioctl+0x41/0x50 > [<ffffffff8d45d9e0>] do_vfs_ioctl+0x3a0/0x5a0 > [<ffffffff8d45dc81>] SyS_ioctl+0xa1/0xc0 > > A related problem is that virtblk_remove() leaks the vd_index_ida index > when something still holds a reference to vblk->disk during hot unplug. > This causes virtio-blk device names to be lost (vda, vdb, etc). > > Fix these issues by protecting vblk->vdev with a mutex and reference > counting vblk so the vd_index_ida index can be removed in all cases. > > Fixes: 48e4043d4529523cbc7fa8dd745bd8e2c45ce1d3 > ("virtio: add virtio disk geometry feature") Should be Fixes: 48e4043d4529 ("virtio: add virtio disk geometry feature") > Reported-by: Lance Digby <ldigby@redhat.com> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > v4: > * Clarify vdev_mutex usage [Stefano and Michael] > > drivers/block/virtio_blk.c | 86 ++++++++++++++++++++++++++++++++++---- > 1 file changed, 78 insertions(+), 8 deletions(-) > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 93468b7c6701..9d21bf0f155e 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -33,6 +33,15 @@ struct virtio_blk_vq { > } ____cacheline_aligned_in_smp; > > struct virtio_blk { > + /* > + * This mutex must be held by anything that may run after > + * virtblk_remove() sets vblk->vdev to NULL. > + * > + * blk-mq, virtqueue processing, and sysfs attribute code paths are > + * shut down before vblk->vdev is set to NULL and therefore do not need > + * to hold this mutex. > + */ > + struct mutex vdev_mutex; > struct virtio_device *vdev; > > /* The disk structure for the kernel. */ > @@ -44,6 +53,13 @@ struct virtio_blk { > /* Process context for config space updates */ > struct work_struct config_work; > > + /* > + * Tracks references from block_device_operations open/release and > + * virtio_driver probe/remove so this object can be freed once no > + * longer in use. > + */ > + refcount_t refs; Using a struct kref might be more idiomatic. > + > /* What host tells us, plus 2 for header & tailer. */ > unsigned int sg_elems; > > @@ -295,10 +311,55 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str) > return err; > } > > +static void virtblk_get(struct virtio_blk *vblk) > +{ > + refcount_inc(&vblk->refs); Should the code even be able to grab a ref if !vblk->vdev? > +} > + > +static void virtblk_put(struct virtio_blk *vblk) > +{ > + if (refcount_dec_and_test(&vblk->refs)) { > + ida_simple_remove(&vd_index_ida, vblk->index); > + mutex_destroy(&vblk->vdev_mutex); > + kfree(vblk); I think that's where putting these cleanups into a release() funtion would be more idiomatic. > + } > +} (...) Looks sane to me.
On Mon, May 04, 2020 at 01:48:34PM +0200, Cornelia Huck wrote: > On Thu, 30 Apr 2020 15:04:42 +0100 > Stefan Hajnoczi <stefanha@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 > > CPU: 0 PID: 1310 Comm: hdio-getgeo Tainted: G OE ------------ 3.10.0-1062.el7.x86_64 #1 > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 > > task: ffff9be5fbfb8000 ti: ffff9be5fa890000 task.ti: ffff9be5fa890000 > > RIP: 0010:[<ffffffffc00e5450>] [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] > > RSP: 0018:ffff9be5fa893dc8 EFLAGS: 00010246 > > RAX: ffff9be5fc3f3400 RBX: ffff9be5fa893e30 RCX: 0000000000000000 > > RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff9be5fbc10b40 > > RBP: ffff9be5fa893dc8 R08: 0000000000000301 R09: 0000000000000301 > > R10: 0000000000000000 R11: 0000000000000000 R12: ffff9be5fdc24680 > > R13: ffff9be5fbc10b40 R14: ffff9be5fbc10480 R15: 0000000000000000 > > FS: 00007f1bfb968740(0000) GS:ffff9be5ffc00000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 0000000000000090 CR3: 000000003a894000 CR4: 0000000000360ff0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Call Trace: > > [<ffffffffc016ac37>] virtblk_getgeo+0x47/0x110 [virtio_blk] > > [<ffffffff8d3f200d>] ? handle_mm_fault+0x39d/0x9b0 > > [<ffffffff8d561265>] blkdev_ioctl+0x1f5/0xa20 > > [<ffffffff8d488771>] block_ioctl+0x41/0x50 > > [<ffffffff8d45d9e0>] do_vfs_ioctl+0x3a0/0x5a0 > > [<ffffffff8d45dc81>] SyS_ioctl+0xa1/0xc0 > > > > A related problem is that virtblk_remove() leaks the vd_index_ida index > > when something still holds a reference to vblk->disk during hot unplug. > > This causes virtio-blk device names to be lost (vda, vdb, etc). > > > > Fix these issues by protecting vblk->vdev with a mutex and reference > > counting vblk so the vd_index_ida index can be removed in all cases. > > > > Fixes: 48e4043d4529523cbc7fa8dd745bd8e2c45ce1d3 > > ("virtio: add virtio disk geometry feature") > > Should be > > Fixes: 48e4043d4529 ("virtio: add virtio disk geometry feature") Yes - it was reported on linux-next so I fixed it up when applying. > > Reported-by: Lance Digby <ldigby@redhat.com> > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > > --- > > v4: > > * Clarify vdev_mutex usage [Stefano and Michael] > > > > drivers/block/virtio_blk.c | 86 ++++++++++++++++++++++++++++++++++---- > > 1 file changed, 78 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > > index 93468b7c6701..9d21bf0f155e 100644 > > --- a/drivers/block/virtio_blk.c > > +++ b/drivers/block/virtio_blk.c > > @@ -33,6 +33,15 @@ struct virtio_blk_vq { > > } ____cacheline_aligned_in_smp; > > > > struct virtio_blk { > > + /* > > + * This mutex must be held by anything that may run after > > + * virtblk_remove() sets vblk->vdev to NULL. > > + * > > + * blk-mq, virtqueue processing, and sysfs attribute code paths are > > + * shut down before vblk->vdev is set to NULL and therefore do not need > > + * to hold this mutex. > > + */ > > + struct mutex vdev_mutex; > > struct virtio_device *vdev; > > > > /* The disk structure for the kernel. */ > > @@ -44,6 +53,13 @@ struct virtio_blk { > > /* Process context for config space updates */ > > struct work_struct config_work; > > > > + /* > > + * Tracks references from block_device_operations open/release and > > + * virtio_driver probe/remove so this object can be freed once no > > + * longer in use. > > + */ > > + refcount_t refs; > > Using a struct kref might be more idiomatic. > > > + > > /* What host tells us, plus 2 for header & tailer. */ > > unsigned int sg_elems; > > > > @@ -295,10 +311,55 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str) > > return err; > > } > > > > +static void virtblk_get(struct virtio_blk *vblk) > > +{ > > + refcount_inc(&vblk->refs); > > Should the code even be able to grab a ref if !vblk->vdev? > > > +} > > + > > +static void virtblk_put(struct virtio_blk *vblk) > > +{ > > + if (refcount_dec_and_test(&vblk->refs)) { > > + ida_simple_remove(&vd_index_ida, vblk->index); > > + mutex_destroy(&vblk->vdev_mutex); > > + kfree(vblk); > > I think that's where putting these cleanups into a release() funtion > would be more idiomatic. > > > + } > > +} > > (...) > > Looks sane to me.
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 93468b7c6701..9d21bf0f155e 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -33,6 +33,15 @@ struct virtio_blk_vq { } ____cacheline_aligned_in_smp; struct virtio_blk { + /* + * This mutex must be held by anything that may run after + * virtblk_remove() sets vblk->vdev to NULL. + * + * blk-mq, virtqueue processing, and sysfs attribute code paths are + * shut down before vblk->vdev is set to NULL and therefore do not need + * to hold this mutex. + */ + struct mutex vdev_mutex; struct virtio_device *vdev; /* The disk structure for the kernel. */ @@ -44,6 +53,13 @@ struct virtio_blk { /* Process context for config space updates */ struct work_struct config_work; + /* + * Tracks references from block_device_operations open/release and + * virtio_driver probe/remove so this object can be freed once no + * longer in use. + */ + refcount_t refs; + /* What host tells us, plus 2 for header & tailer. */ unsigned int sg_elems; @@ -295,10 +311,55 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str) return err; } +static void virtblk_get(struct virtio_blk *vblk) +{ + refcount_inc(&vblk->refs); +} + +static void virtblk_put(struct virtio_blk *vblk) +{ + if (refcount_dec_and_test(&vblk->refs)) { + ida_simple_remove(&vd_index_ida, vblk->index); + mutex_destroy(&vblk->vdev_mutex); + kfree(vblk); + } +} + +static int virtblk_open(struct block_device *bd, fmode_t mode) +{ + struct virtio_blk *vblk = bd->bd_disk->private_data; + int ret = 0; + + mutex_lock(&vblk->vdev_mutex); + + if (vblk->vdev) + virtblk_get(vblk); + else + ret = -ENXIO; + + mutex_unlock(&vblk->vdev_mutex); + return ret; +} + +static void virtblk_release(struct gendisk *disk, fmode_t mode) +{ + struct virtio_blk *vblk = disk->private_data; + + virtblk_put(vblk); +} + /* We provide getgeo only to please some old bootloader/partitioning tools */ static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo) { struct virtio_blk *vblk = bd->bd_disk->private_data; + int ret = 0; + + mutex_lock(&vblk->vdev_mutex); + + if (!vblk->vdev) { + ret = -ENXIO; + goto out; + } /* see if the host passed in geometry config */ if (virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_GEOMETRY)) { @@ -314,11 +375,15 @@ static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo) geo->sectors = 1 << 5; geo->cylinders = get_capacity(bd->bd_disk) >> 11; } - return 0; +out: + mutex_unlock(&vblk->vdev_mutex); + return ret; } static const struct block_device_operations virtblk_fops = { .owner = THIS_MODULE, + .open = virtblk_open, + .release = virtblk_release, .getgeo = virtblk_getgeo, }; @@ -655,6 +720,10 @@ static int virtblk_probe(struct virtio_device *vdev) goto out_free_index; } + /* This reference is dropped in virtblk_remove(). */ + refcount_set(&vblk->refs, 1); + mutex_init(&vblk->vdev_mutex); + vblk->vdev = vdev; vblk->sg_elems = sg_elems; @@ -820,8 +889,6 @@ static int virtblk_probe(struct virtio_device *vdev) static void virtblk_remove(struct virtio_device *vdev) { struct virtio_blk *vblk = vdev->priv; - int index = vblk->index; - int refc; /* Make sure no work handler is accessing the device. */ flush_work(&vblk->config_work); @@ -831,18 +898,21 @@ static void virtblk_remove(struct virtio_device *vdev) blk_mq_free_tag_set(&vblk->tag_set); + mutex_lock(&vblk->vdev_mutex); + /* Stop all the virtqueues. */ vdev->config->reset(vdev); - refc = kref_read(&disk_to_dev(vblk->disk)->kobj.kref); + /* Virtqueues are stopped, nothing can use vblk->vdev anymore. */ + vblk->vdev = NULL; + put_disk(vblk->disk); vdev->config->del_vqs(vdev); kfree(vblk->vqs); - kfree(vblk); - /* Only free device id if we don't have any users */ - if (refc == 1) - ida_simple_remove(&vd_index_ida, index); + mutex_unlock(&vblk->vdev_mutex); + + virtblk_put(vblk); } #ifdef CONFIG_PM_SLEEP
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-getgeo Tainted: G OE ------------ 3.10.0-1062.el7.x86_64 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 task: ffff9be5fbfb8000 ti: ffff9be5fa890000 task.ti: ffff9be5fa890000 RIP: 0010:[<ffffffffc00e5450>] [<ffffffffc00e5450>] virtio_check_driver_offered_feature+0x10/0x90 [virtio] RSP: 0018:ffff9be5fa893dc8 EFLAGS: 00010246 RAX: ffff9be5fc3f3400 RBX: ffff9be5fa893e30 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff9be5fbc10b40 RBP: ffff9be5fa893dc8 R08: 0000000000000301 R09: 0000000000000301 R10: 0000000000000000 R11: 0000000000000000 R12: ffff9be5fdc24680 R13: ffff9be5fbc10b40 R14: ffff9be5fbc10480 R15: 0000000000000000 FS: 00007f1bfb968740(0000) GS:ffff9be5ffc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000090 CR3: 000000003a894000 CR4: 0000000000360ff0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: [<ffffffffc016ac37>] virtblk_getgeo+0x47/0x110 [virtio_blk] [<ffffffff8d3f200d>] ? handle_mm_fault+0x39d/0x9b0 [<ffffffff8d561265>] blkdev_ioctl+0x1f5/0xa20 [<ffffffff8d488771>] block_ioctl+0x41/0x50 [<ffffffff8d45d9e0>] do_vfs_ioctl+0x3a0/0x5a0 [<ffffffff8d45dc81>] SyS_ioctl+0xa1/0xc0 A related problem is that virtblk_remove() leaks the vd_index_ida index when something still holds a reference to vblk->disk during hot unplug. This causes virtio-blk device names to be lost (vda, vdb, etc). Fix these issues by protecting vblk->vdev with a mutex and reference counting vblk so the vd_index_ida index can be removed in all cases. Fixes: 48e4043d4529523cbc7fa8dd745bd8e2c45ce1d3 ("virtio: add virtio disk geometry feature") Reported-by: Lance Digby <ldigby@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- v4: * Clarify vdev_mutex usage [Stefano and Michael] drivers/block/virtio_blk.c | 86 ++++++++++++++++++++++++++++++++++---- 1 file changed, 78 insertions(+), 8 deletions(-)