Messages in this thread Patch in this message | | | Date | Wed, 28 Mar 2012 11:40:33 +0800 | From | Ren Mingxin <> | Subject | [RFC PATCH] virtio_blk: Checking "private_data" to avoid kernel panic when hotplugging |
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Hi,
On guest with upstream's kernel(3.3.0-rc7), I mounted virtblk as: a) # mkfs /dev/vda b) # mount /dev/vda /mnt c) # cd /mnt
Then I did hotplug for virtblk via virsh on host as: a) # sudo virsh detach-disk guest vda b) # sudo virsh attach-disk guest /media/data/test.img vda
I encountered guest's kernel panic (*probability * *event*)whose backtrace liked this:
PID: 2496 TASK: ffff88001f5de080 CPU: 0 COMMAND: "blkid" #0 [ffff88001afdbb00] machine_kexec at ffffffff81031fcb #1 [ffff88001afdbb60] crash_kexec at ffffffff810b8f72 #2 [ffff88001afdbc30] oops_end at ffffffff814f04b0 #3 [ffff88001afdbc60] die at ffffffff8100f26b #4 [ffff88001afdbc90] do_general_protection at ffffffff814f0042 #5 [ffff88001afdbcc0] general_protection at ffffffff814ef815 [exception RIP: virtio_check_driver_offered_feature+27] RIP: ffffffffa00540cb RSP: ffff88001afdbd78 RFLAGS: 00010206 RAX: ffffffff810ffde0 RBX: ffff88001f14a800 RCX: 000000004cf0758b RDX: 4ce86d8b4ce0658b RSI: 0000000000000007 RDI: ffffffff81a970a0 RBP: ffff88001afdbd78 R8: ffffffffa009d060 R9: 0000000000000100 R10: 0000000000000006 R11: 0000000000000246 R12: 000000000000101d R13: 0000000000005331 R14: ffffffff81a970a0 R15: 0000000000000000 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 #6 [ffff88001afdbd80] virtblk_ioctl at ffffffffa009c459 [virtio_blk] #7 [ffff88001afdbdc0] __blkdev_driver_ioctl at ffffffff81257317 #8 [ffff88001afdbe00] blkdev_ioctl at ffffffff8125779d #9 [ffff88001afdbe50] block_ioctl at ffffffff811aec5c #10 [ffff88001afdbe60] vfs_ioctl at ffffffff81189342 #11 [ffff88001afdbea0] do_vfs_ioctl at ffffffff811894e4 #12 [ffff88001afdbf30] sys_ioctl at ffffffff81189a61 #13 [ffff88001afdbf80] system_call_fastpath at ffffffff8100b0f2 RIP: 0000003f566dd847 RSP: 00007fffa23e6130 RFLAGS: 00010202 RAX: 0000000000000010 RBX: ffffffff8100b0f2 RCX: 0000000000000008 RDX: 0000000000000000 RSI: 0000000000005331 RDI: 0000000000000003 RBP: 0000000040000000 R8: 0000003f5699b580 R9: 0000000000000100 R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000000000 R13: 0000003f59020ba0 R14: 0000000000000003 R15: 000000000241f030 ORIG_RAX: 0000000000000010 CS: 0033 SS: 002b
This panic was triggered by the command of "blkid" in udev's rule "60-persistent-storage.rules".
So, when the virtblk was reattached, command "blkid" probed filesystem metadata of disks. At that moment, virtblk_ioctl() was called, but the data of "virtio_blk" "bdev->bd_disk->private_data" pointing to may not be updated for the sync reason.
This patch do this check to avoid panic.
Any comment will be appreciated.
Signed-off-by: Ren Mingxin <renmx@cn.fujitsu.com> --- virtio_blk.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index c4a60ba..4ac81f8 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -245,6 +245,12 @@ static int virtblk_ioctl(struct block_device *bdev, fmode_t mode, struct virtio_blk *vblk = disk->private_data;
/* + * Check whether the private data pointer has been updated. + */ + if (vblk != vblk->vdev->priv) + return -EFAULT; + + /* * Only allow the generic SCSI ioctls if the host can support it. */ if (!virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_SCSI))
Thanks, Ren
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