dm: fix dax_dev NULL dereference
diff mbox series

Message ID 20190730113708.14660-1-pagupta@redhat.com
State New
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Series
  • dm: fix dax_dev NULL dereference
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Commit Message

Pankaj Gupta July 30, 2019, 11:37 a.m. UTC
'Murphy Zhou' reports[1] hitting the panic when running xfstests 
  generic/108 on pmem ramdisk. In his words:

   This test is simulating partial disk error when calling fsync():
   create a lvm vg which consists of 2 disks:
   one scsi_debug disk; one other disk I specified, pmem ramdisk in this case.
   create lv in this vg and write to it, make sure writing across 2 disks;
   offline scsi_debug disk;
   write again to allocated area;
   expect fsync: IO error.
   If one of the disks is pmem ramdisk, it reproduces every time on my setup,
   on v5.3-rc2+.
   The mount -o dax option is not required to reproduce this panic.
   ...

  Fix this by returning false from 'device_synchronous' function when dax_dev
  is NULL.

 [ 1984.878208] BUG: kernel NULL pointer dereference, address: 00000000000002d0
 [ 1984.882546] #PF: supervisor read access in kernel mode
 [ 1984.885664] #PF: error_code(0x0000) - not-present page
 [ 1984.888626] PGD 0 P4D 0
 [ 1984.890140] Oops: 0000 [#1] SMP PTI
 ...
 ...
 [ 1984.943682] Call Trace:
 [ 1984.945007]  device_synchronous+0xe/0x20 [dm_mod]
 [ 1984.947328]  stripe_iterate_devices+0x48/0x60 [dm_mod]
 [ 1984.949947]  ? dm_set_device_limits+0x130/0x130 [dm_mod]
 [ 1984.952516]  dm_table_supports_dax+0x39/0x90 [dm_mod]
 [ 1984.954989]  dm_table_set_restrictions+0x248/0x5d0 [dm_mod]
 [ 1984.957685]  dm_setup_md_queue+0x66/0x110 [dm_mod]
 [ 1984.960280]  table_load+0x1e3/0x390 [dm_mod]
 [ 1984.962491]  ? retrieve_status+0x1c0/0x1c0 [dm_mod]
 [ 1984.964910]  ctl_ioctl+0x1d3/0x550 [dm_mod]
 [ 1984.967006]  ? path_lookupat+0xf4/0x200
 [ 1984.968890]  dm_ctl_ioctl+0xa/0x10 [dm_mod]
 [ 1984.970920]  do_vfs_ioctl+0xa9/0x630
 [ 1984.972701]  ksys_ioctl+0x60/0x90
 [ 1984.974335]  __x64_sys_ioctl+0x16/0x20
 [ 1984.976221]  do_syscall_64+0x5b/0x1d0
 [ 1984.978091]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

 [1] https://lore.kernel.org/linux-fsdevel/2011806368.5335560.1564469373050.JavaMail.zimbra@redhat.com/T/#mac662eb50b9d7bd282b23e6e8625a3f7a4687506

Fixes: 2e9ee0955d3c ("dm: enable synchronous dax")
Reported-by: jencce.kernel@gmail.com
Tested-by: jencce.kernel@gmail.com
Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 drivers/md/dm-table.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Pankaj Gupta July 30, 2019, 11:38 a.m. UTC | #1
+CC [jencce.kernel@gmail.com]
> 
> 
>   'Murphy Zhou' reports[1] hitting the panic when running xfstests
>   generic/108 on pmem ramdisk. In his words:
> 
>    This test is simulating partial disk error when calling fsync():
>    create a lvm vg which consists of 2 disks:
>    one scsi_debug disk; one other disk I specified, pmem ramdisk in this
>    case.
>    create lv in this vg and write to it, make sure writing across 2 disks;
>    offline scsi_debug disk;
>    write again to allocated area;
>    expect fsync: IO error.
>    If one of the disks is pmem ramdisk, it reproduces every time on my setup,
>    on v5.3-rc2+.
>    The mount -o dax option is not required to reproduce this panic.
>    ...
> 
>   Fix this by returning false from 'device_synchronous' function when dax_dev
>   is NULL.
> 
>  [ 1984.878208] BUG: kernel NULL pointer dereference, address:
>  00000000000002d0
>  [ 1984.882546] #PF: supervisor read access in kernel mode
>  [ 1984.885664] #PF: error_code(0x0000) - not-present page
>  [ 1984.888626] PGD 0 P4D 0
>  [ 1984.890140] Oops: 0000 [#1] SMP PTI
>  ...
>  ...
>  [ 1984.943682] Call Trace:
>  [ 1984.945007]  device_synchronous+0xe/0x20 [dm_mod]
>  [ 1984.947328]  stripe_iterate_devices+0x48/0x60 [dm_mod]
>  [ 1984.949947]  ? dm_set_device_limits+0x130/0x130 [dm_mod]
>  [ 1984.952516]  dm_table_supports_dax+0x39/0x90 [dm_mod]
>  [ 1984.954989]  dm_table_set_restrictions+0x248/0x5d0 [dm_mod]
>  [ 1984.957685]  dm_setup_md_queue+0x66/0x110 [dm_mod]
>  [ 1984.960280]  table_load+0x1e3/0x390 [dm_mod]
>  [ 1984.962491]  ? retrieve_status+0x1c0/0x1c0 [dm_mod]
>  [ 1984.964910]  ctl_ioctl+0x1d3/0x550 [dm_mod]
>  [ 1984.967006]  ? path_lookupat+0xf4/0x200
>  [ 1984.968890]  dm_ctl_ioctl+0xa/0x10 [dm_mod]
>  [ 1984.970920]  do_vfs_ioctl+0xa9/0x630
>  [ 1984.972701]  ksys_ioctl+0x60/0x90
>  [ 1984.974335]  __x64_sys_ioctl+0x16/0x20
>  [ 1984.976221]  do_syscall_64+0x5b/0x1d0
>  [ 1984.978091]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
>  [1]
>  https://lore.kernel.org/linux-fsdevel/2011806368.5335560.1564469373050.JavaMail.zimbra@redhat.com/T/#mac662eb50b9d7bd282b23e6e8625a3f7a4687506
> 
> Fixes: 2e9ee0955d3c ("dm: enable synchronous dax")
> Reported-by: jencce.kernel@gmail.com
> Tested-by: jencce.kernel@gmail.com
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  drivers/md/dm-table.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index caaee8032afe..b065845c1bdd 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -894,6 +894,9 @@ int device_supports_dax(struct dm_target *ti, struct
> dm_dev *dev,
>  static int device_synchronous(struct dm_target *ti, struct dm_dev *dev,
>  				       sector_t start, sector_t len, void *data)
>  {
> +	if (!dev->dax_dev)
> +		return false;
> +
>  	return dax_synchronous(dev->dax_dev);
>  }
>  
> --
> 2.20.1
> 
>
Mike Snitzer July 30, 2019, 7:07 p.m. UTC | #2
I staged the fix (which I tweaked) here:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.3&id=95b9ebb78c4c733f8912a195fbd0bc19960e726e

Also, please note this additional related commit that just serves to
improve a related function name and clean up some whitespace:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.3&id=f965f935a89bb174fd3f6d6b51bba91c1ed258c5

I'll likely send these to Linus for 5.2-rc3 later this week.

Thanks,
Mike
Dan Williams July 30, 2019, 9:38 p.m. UTC | #3
On Tue, Jul 30, 2019 at 12:07 PM Mike Snitzer <snitzer@redhat.com> wrote:
>
> I staged the fix (which I tweaked) here:
> https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.3&id=95b9ebb78c4c733f8912a195fbd0bc19960e726e

Thanks for picking this up Mike, but I'd prefer to just teach
dax_synchronous() to return false if the passed in dax_dev is NULL.
Thoughts?
Mike Snitzer July 30, 2019, 10:01 p.m. UTC | #4
On Tue, Jul 30 2019 at  5:38pm -0400,
Dan Williams <dan.j.williams@intel.com> wrote:

> On Tue, Jul 30, 2019 at 12:07 PM Mike Snitzer <snitzer@redhat.com> wrote:
> >
> > I staged the fix (which I tweaked) here:
> > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.3&id=95b9ebb78c4c733f8912a195fbd0bc19960e726e
> 
> Thanks for picking this up Mike, but I'd prefer to just teach
> dax_synchronous() to return false if the passed in dax_dev is NULL.
> Thoughts?

I considered that too but I moved away from it because I'm so used to
the various block interfaces requiring the caller pass a non-NULL
pointer (e.g. request_queue):

$ grep -ri return drivers/md/dm-table.c | grep \&\&
drivers/md/dm-table.c:        return dev->dax_dev && dax_synchronous(dev->dax_dev);
drivers/md/dm-table.c:        return q && blk_queue_zoned_model(q) == *zoned_model;
drivers/md/dm-table.c:        return q && blk_queue_zone_sectors(q) == *zone_sectors;
drivers/md/dm-table.c:        return q && (q->queue_flags & flush);
drivers/md/dm-table.c:        return q && blk_queue_nonrot(q);
drivers/md/dm-table.c:        return q && !blk_queue_add_random(q);
drivers/md/dm-table.c:        return q && !q->limits.max_write_same_sectors;
drivers/md/dm-table.c:        return q && !q->limits.max_write_zeroes_sectors;
drivers/md/dm-table.c:        return q && !blk_queue_discard(q);
drivers/md/dm-table.c:        return q && !blk_queue_secure_erase(q);
drivers/md/dm-table.c:        return q && bdi_cap_stable_pages_required(q->backing_dev_info);

I'm fine with however you'd like to skin this cat though.

Just let me know and I'll keep/drop this patch accordingly.

Thanks,
Mike
Dan Williams July 30, 2019, 10:15 p.m. UTC | #5
On Tue, Jul 30, 2019 at 3:01 PM Mike Snitzer <snitzer@redhat.com> wrote:
>
> On Tue, Jul 30 2019 at  5:38pm -0400,
> Dan Williams <dan.j.williams@intel.com> wrote:
>
> > On Tue, Jul 30, 2019 at 12:07 PM Mike Snitzer <snitzer@redhat.com> wrote:
> > >
> > > I staged the fix (which I tweaked) here:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.3&id=95b9ebb78c4c733f8912a195fbd0bc19960e726e
> >
> > Thanks for picking this up Mike, but I'd prefer to just teach
> > dax_synchronous() to return false if the passed in dax_dev is NULL.
> > Thoughts?
>
> I considered that too but I moved away from it because I'm so used to
> the various block interfaces requiring the caller pass a non-NULL
> pointer (e.g. request_queue):
>
> $ grep -ri return drivers/md/dm-table.c | grep \&\&
> drivers/md/dm-table.c:        return dev->dax_dev && dax_synchronous(dev->dax_dev);
> drivers/md/dm-table.c:        return q && blk_queue_zoned_model(q) == *zoned_model;
> drivers/md/dm-table.c:        return q && blk_queue_zone_sectors(q) == *zone_sectors;
> drivers/md/dm-table.c:        return q && (q->queue_flags & flush);
> drivers/md/dm-table.c:        return q && blk_queue_nonrot(q);
> drivers/md/dm-table.c:        return q && !blk_queue_add_random(q);
> drivers/md/dm-table.c:        return q && !q->limits.max_write_same_sectors;
> drivers/md/dm-table.c:        return q && !q->limits.max_write_zeroes_sectors;
> drivers/md/dm-table.c:        return q && !blk_queue_discard(q);
> drivers/md/dm-table.c:        return q && !blk_queue_secure_erase(q);
> drivers/md/dm-table.c:        return q && bdi_cap_stable_pages_required(q->backing_dev_info);
>
> I'm fine with however you'd like to skin this cat though.
>
> Just let me know and I'll keep/drop this patch accordingly.

Ok, since you've already got it queued, and there are no other
required "if (!dax_dev)" fixups go ahead with what you have.

    Acked-by: Dan Williams <dan.j.williams@intel.com>

I just reserve the right to go push it down a level if the kernel ever
grows more dax_synchronous() users that do that safety check.
Pankaj Gupta July 31, 2019, 3:50 a.m. UTC | #6
> 
> I staged the fix (which I tweaked) here:
> https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.3&id=95b9ebb78c4c733f8912a195fbd0bc19960e726e
> 
> Also, please note this additional related commit that just serves to
> improve a related function name and clean up some whitespace:
> https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.3&id=f965f935a89bb174fd3f6d6b51bba91c1ed258c5
> 
> I'll likely send these to Linus for 5.2-rc3 later this week.

o.k

Thank you,
Pankaj

> 
> Thanks,
> Mike
>

Patch
diff mbox series

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index caaee8032afe..b065845c1bdd 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -894,6 +894,9 @@  int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
 static int device_synchronous(struct dm_target *ti, struct dm_dev *dev,
 				       sector_t start, sector_t len, void *data)
 {
+	if (!dev->dax_dev)
+		return false;
+
 	return dax_synchronous(dev->dax_dev);
 }