loop: fix to a race condition due to the early registration of device (a8c1d064) · Commits · 戴 / test

The early device registration made possible a race leading to allocations of disks with wrong minors. This patch moves the device registration further down the loop_init function to make the race infeasible. Found by Linux Driver Verification project (linuxtesting.org). Signed-off-by:

Anton Volkov <avolkov@ispras.ru> Reviewed-by:

Ming Lei <ming.lei@redhat.com> Reviewed-by:

Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -1996,10 +1996,6 @@ static int __init loop_init(void)
		struct loop_device *lo;
		int err;

		err = misc_register(&loop_misc);
		if (err < 0)
		return err;

		part_shift = 0;
		if (max_part > 0) {
		part_shift = fls(max_part);
		@@ -2017,12 +2013,12 @@ static int __init loop_init(void)

		if ((1UL << part_shift) > DISK_MAX_PARTS) {
		err = -EINVAL;
		goto misc_out;
		goto err_out;
		}

		if (max_loop > 1UL << (MINORBITS - part_shift)) {
		err = -EINVAL;
		goto misc_out;
		goto err_out;
		}

		/*
		@@ -2041,6 +2037,11 @@ static int __init loop_init(void)
		range = 1UL << MINORBITS;
		}

		err = misc_register(&loop_misc);
		if (err < 0)
		goto err_out;


		if (register_blkdev(LOOP_MAJOR, "loop")) {
		err = -EIO;
		goto misc_out;
		@@ -2060,6 +2061,7 @@ static int __init loop_init(void)

		misc_out:
		misc_deregister(&loop_misc);
		err_out:
		return err;
		}

Admin message