cfq-iosched: handle failure of cfq group allocation

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 cd1604f ("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 <[email protected]> Acked-by: Tejun Heo <[email protected]> Acked-by: Vivek Goyal <[email protected]> Fixes: cd1604f ("blkcg: factor out blkio_group creation") Cc: [email protected] Signed-off-by: Jens Axboe <[email protected]>
xlks · Feb 9, 2015 · 69abaff · 69abaff
1 parent 9f9ee1f
commit 69abaff
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
@@ -3590,6 +3590,11 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
 
 	blkcg = bio_blkcg(bio);
 	cfqg = cfq_lookup_create_cfqg(cfqd, blkcg);
+	if (!cfqg) {
+		cfqq = &cfqd->oom_cfqq;
+		goto out;
+	}
+
 	cfqq = cic_to_cfqq(cic, is_sync);
 
 	/*
@@ -3626,7 +3631,7 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
 		} else
 			cfqq = &cfqd->oom_cfqq;
 	}
-
+out:
 	if (new_cfqq)
 		kmem_cache_free(cfq_pool, new_cfqq);