On Thu, Dec 17, 2015 at 2:26 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > When tearing down a block device early in its lifetime, userspace may > still be performing discovery actions like blkdev_ioctl() to re-read > partitions. > > The nvdimm_revalidate_disk() implementation depends on > disk->driverfs_dev to be valid at entry. However, it is set to NULL in > del_gendisk() and fatally this is happening *before* the disk device is > deleted from userspace view. > > There's no reason for del_gendisk() to clear ->driverfs_dev. That > device is the parent of the disk. It is guaranteed to not be freed > until the disk, as a child, drops its ->parent reference. > > We could also fix this issue locally in nvdimm_revalidate_disk() by > using disk_to_dev(disk)->parent, but lets fix it globally since > ->driverfs_dev follows the lifetime of the parent. Longer term we > should probably just add a @parent parameter to add_disk(), and stop > carrying this pointer in the gendisk. > > BUG: unable to handle kernel NULL pointer dereference at (null) > IP: [<ffffffffa00340a8>] nvdimm_revalidate_disk+0x18/0x90 [libnvdimm] > CPU: 2 PID: 538 Comm: systemd-udevd Tainted: G O 4.4.0-rc5 #2257 > [..] > Call Trace: > [<ffffffff8143e5c7>] rescan_partitions+0x87/0x2c0 > [<ffffffff810f37f9>] ? __lock_is_held+0x49/0x70 > [<ffffffff81438c62>] __blkdev_reread_part+0x72/0xb0 > [<ffffffff81438cc5>] blkdev_reread_part+0x25/0x40 > [<ffffffff8143982d>] blkdev_ioctl+0x4fd/0x9c0 > [<ffffffff811246c9>] ? current_kernel_time64+0x69/0xd0 > [<ffffffff812916dd>] block_ioctl+0x3d/0x50 > [<ffffffff81264c38>] do_vfs_ioctl+0x308/0x560 > [<ffffffff8115dbd1>] ? __audit_syscall_entry+0xb1/0x100 > [<ffffffff810031d6>] ? do_audit_syscall_entry+0x66/0x70 > [<ffffffff81264f09>] SyS_ioctl+0x79/0x90 > [<ffffffff81902672>] entry_SYSCALL_64_fastpath+0x12/0x76 > > Reported-by: Robert Hu <robert.hu@xxxxxxxxx> > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> I forgot to add: Cc: <stable@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
