4.2.8-ckt7 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Eric Wheeler <git@xxxxxxxxxxxxxxxxxx> commit 9b299728ed777428b3908ac72ace5f8f84b97789 upstream. Fix null pointer dereference by changing register_cache() to return an int instead of being void. This allows it to return -ENOMEM or -ENODEV and enables upper layers to handle the OOM case without NULL pointer issues. See this thread: http://thread.gmane.org/gmane.linux.kernel.bcache.devel/3521 Fixes this error: gargamel:/sys/block/md5/bcache# echo /dev/sdh2 > /sys/fs/bcache/register bcache: register_cache() error opening sdh2: cannot allocate memory BUG: unable to handle kernel NULL pointer dereference at 00000000000009b8 IP: [<ffffffffc05a7e8d>] cache_set_flush+0x102/0x15c [bcache] PGD 120dff067 PUD 1119a3067 PMD 0 Oops: 0000 [#1] SMP Modules linked in: veth ip6table_filter ip6_tables (...) CPU: 4 PID: 3371 Comm: kworker/4:3 Not tainted 4.4.2-amd64-i915-volpreempt-20160213bc1 #3 Hardware name: System manufacturer System Product Name/P8H67-M PRO, BIOS 3904 04/27/2013 Workqueue: events cache_set_flush [bcache] task: ffff88020d5dc280 ti: ffff88020b6f8000 task.ti: ffff88020b6f8000 RIP: 0010:[<ffffffffc05a7e8d>] [<ffffffffc05a7e8d>] cache_set_flush+0x102/0x15c [bcache] Signed-off-by: Eric Wheeler <bcache@xxxxxxxxxxxxxxxxxx> Tested-by: Marc MERLIN <marc@xxxxxxxxxxx> Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx> --- drivers/md/bcache/super.c | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-) diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 45cedc7..d7ce93e 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1863,11 +1863,12 @@ static int cache_alloc(struct cache_sb *sb, struct cache *ca) return 0; } -static void register_cache(struct cache_sb *sb, struct page *sb_page, +static int register_cache(struct cache_sb *sb, struct page *sb_page, struct block_device *bdev, struct cache *ca) { char name[BDEVNAME_SIZE]; - const char *err = "cannot allocate memory"; + const char *err = NULL; + int ret = 0; memcpy(&ca->sb, sb, sizeof(struct cache_sb)); ca->bdev = bdev; @@ -1882,27 +1883,35 @@ static void register_cache(struct cache_sb *sb, struct page *sb_page, if (blk_queue_discard(bdev_get_queue(ca->bdev))) ca->discard = CACHE_DISCARD(&ca->sb); - if (cache_alloc(sb, ca) != 0) + ret = cache_alloc(sb, ca); + if (ret != 0) goto err; - err = "error creating kobject"; - if (kobject_add(&ca->kobj, &part_to_dev(bdev->bd_part)->kobj, "bcache")) - goto err; + if (kobject_add(&ca->kobj, &part_to_dev(bdev->bd_part)->kobj, "bcache")) { + err = "error calling kobject_add"; + ret = -ENOMEM; + goto out; + } mutex_lock(&bch_register_lock); err = register_cache_set(ca); mutex_unlock(&bch_register_lock); - if (err) - goto err; + if (err) { + ret = -ENODEV; + goto out; + } pr_info("registered cache device %s", bdevname(bdev, name)); + out: kobject_put(&ca->kobj); - return; + err: - pr_notice("error opening %s: %s", bdevname(bdev, name), err); - goto out; + if (err) + pr_notice("error opening %s: %s", bdevname(bdev, name), err); + + return ret; } /* Global interfaces/init */ @@ -2000,7 +2009,8 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr, if (!ca) goto err_close; - register_cache(sb, sb_page, bdev, ca); + if (register_cache(sb, sb_page, bdev, ca) != 0) + goto err_close; } out: if (sb_page) -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html