Message ID | 20190730113708.14660-1-pagupta@redhat.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | dm: fix dax_dev NULL dereference | expand |
+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 > >
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
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?
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
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.
> > 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 >
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); }