Eric Lee / smarc-ti-linux-kernel

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Commit e83be4d104e90d3f4cee593b6a8c5d1b5743751f

Authored by Konstantin Khlebnikov
Committed by Greg Kroah-Hartman
1 parent e78f848979

cfq-iosched: handle failure of cfq group allocation 

commit 69abaffec7d47a083739b79e3066cb3730eba72e upstream.

Cfq_lookup_create_cfqg() allocates struct blkcg_gq using GFP_ATOMIC.
In cfq_find_alloc_queue() possible allocation failure is not handled.
As a result kernel oopses on NULL pointer dereference when
cfq_link_cfqq_cfqg() calls cfqg_get() for NULL pointer.

Bug was introduced in v3.5 in commit cd1604fab4f9 ("blkcg: factor
out blkio_group creation"). Prior to that commit cfq group lookup
had returned pointer to root group as fallback.

This patch handles this error using existing fallback oom_cfqq.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Fixes: cd1604fab4f9 ("blkcg: factor out blkio_group creation")
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Showing 1 changed file with 6 additions and 1 deletions Side-by-side Diff

... ... @@ -3590,6 +3590,11 @@
3590 3590  
3591 3591 blkcg = bio_blkcg(bio);
3592 3592 cfqg = cfq_lookup_create_cfqg(cfqd, blkcg);
  3593 + if (!cfqg) {
  3594 + cfqq = &cfqd->oom_cfqq;
  3595 + goto out;
  3596 + }
  3597 +
3593 3598 cfqq = cic_to_cfqq(cic, is_sync);
3594 3599  
3595 3600 /*
... ... @@ -3626,7 +3631,7 @@
3626 3631 } else
3627 3632 cfqq = &cfqd->oom_cfqq;
3628 3633 }
3629   -
  3634 +out:
3630 3635 if (new_cfqq)
3631 3636 kmem_cache_free(cfq_pool, new_cfqq);
3632 3637