This is a note to let you know that I've just added the patch titled
block: fix del_gendisk() vs blkdev_ioctl crash
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
block-fix-del_gendisk-vs-blkdev_ioctl-crash.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ac34f15e0c6d2fd58480052b6985f6991fb53bcc Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@xxxxxxxxx>
Date: Tue, 29 Dec 2015 14:02:29 -0800
Subject: block: fix del_gendisk() vs blkdev_ioctl crash
From: Dan Williams <dan.j.williams@xxxxxxxxx>
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@xxxxxxx>
Cc: Jens Axboe <axboe@xxxxxx>
Reported-by: Robert Hu <robert.hu@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
Patches currently in stable-queue which might be from dan.j.williams@xxxxxxxxx are
queue-4.4/block-fix-del_gendisk-vs-blkdev_ioctl-crash.patch
queue-4.4/x86-pmem-fix-broken-__copy_user_nocache-cache-bypass-assumptions.patch