Commit a8c1d064 authored by Anton Volkov's avatar Anton Volkov Committed by Jens Axboe

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: default avatarAnton Volkov <avolkov@ispras.ru>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b3193bc0
......@@ -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;
}
......
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