From a8c1d064d3e80aa9e3ca39e908391e433cc53f78 Mon Sep 17 00:00:00 2001 From: Anton Volkov Date: Mon, 7 Aug 2017 15:37:50 +0300 Subject: [PATCH] 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 Reviewed-by: Ming Lei Reviewed-by: Johannes Thumshirn Signed-off-by: Jens Axboe --- drivers/block/loop.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index ef8334949b42..2fbd4089c20e 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; } -- 2.20.1