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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>
hifive-unleashed-5.1
Anton Volkov 2017-08-07 15:37:50 +03:00 committed by Jens Axboe
parent b3193bc0dc
commit a8c1d064d3
1 changed files with 8 additions and 6 deletions
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14
drivers/block/loop.c
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@ -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;
}