loop: fix to a race condition due to the early registration of device
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>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ef83349..2fbd4089 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -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;
}
