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| author | Dan Williams <dan.j.williams@intel.com> | 2015-12-29 14:02:29 -0800 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2016-01-09 06:35:12 -0800 |
| commit | ac34f15e0c6d2fd58480052b6985f6991fb53bcc (patch) | |
| tree | 36515e8456da646eaf84d82a9b0743ec3dd9bdb6 /block | |
| parent | 5a023cdba50c5f5f2bc351783b3131699deb3937 (diff) | |
| download | lwn-ac34f15e0c6d2fd58480052b6985f6991fb53bcc.tar.gz lwn-ac34f15e0c6d2fd58480052b6985f6991fb53bcc.zip | |
block: fix del_gendisk() vs blkdev_ioctl crash
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@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/genhd.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/block/genhd.c b/block/genhd.c index e5cafa51567c..1a971bebbbfe 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); |