| From ac34f15e0c6d2fd58480052b6985f6991fb53bcc Mon Sep 17 00:00:00 2001 |
| From: Dan Williams <dan.j.williams@intel.com> |
| Date: Tue, 29 Dec 2015 14:02:29 -0800 |
| Subject: block: fix del_gendisk() vs blkdev_ioctl crash |
| |
| From: Dan Williams <dan.j.williams@intel.com> |
| |
| commit ac34f15e0c6d2fd58480052b6985f6991fb53bcc upstream. |
| |
| 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 |
| |
| Cc: Jan Kara <jack@suse.cz> |
| Cc: Jens Axboe <axboe@fb.com> |
| Reported-by: Robert Hu <robert.hu@intel.com> |
| Signed-off-by: Dan Williams <dan.j.williams@intel.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| block/genhd.c | 1 - |
| 1 file changed, 1 deletion(-) |
| |
| --- a/block/genhd.c |
| +++ b/block/genhd.c |
| @@ -664,7 +664,6 @@ void del_gendisk(struct gendisk *disk) |
| |
| kobject_put(disk->part0.holder_dir); |
| kobject_put(disk->slave_dir); |
| - disk->driverfs_dev = NULL; |
| if (!sysfs_deprecated) |
| sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk))); |
| pm_runtime_set_memalloc_noio(disk_to_dev(disk), false); |
