bcache: cleaned up error handling around register_cache() (9b299728) · Commits · 戴 / test

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@linux.ewheeler.net> Tested-by:

Marc MERLIN <marc@merlins.org> Cc: <stable@vger.kernel.org>

drivers/md/bcache/super.c

+22 −12

Original line number	Diff line number	Diff line
		@@ -1835,11 +1835,12 @@ 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;
		@@ -1854,27 +1855,35 @@ 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:
		if (err)
		pr_notice("error opening %s: %s", bdevname(bdev, name), err);
		goto out;

		return ret;
		}

		/* Global interfaces/init */
		@@ -1972,7 +1981,8 @@ 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)

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