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authorDan Williams <dan.j.williams@intel.com>2015-12-29 14:02:29 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-04-27 09:09:34 +0200
commit6ddbac9aa800b99761a05ba520d62a0d8063a5b8 (patch)
treedadf3816bd0b0efa04a68ff9e3d420cdf088b387
parentd1cc3cdd39e90e70ee5fc9a766ad3a6c61426fa8 (diff)
block: fix del_gendisk() vs blkdev_ioctl crash
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>
-rw-r--r--block/genhd.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/block/genhd.c b/block/genhd.c
index a5bed6bc869d..3032453a89e6 100644
--- 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);