ublk: fix use-after-free in ublk_partition_scan_work #463
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A race condition exists between the async partition scan work and device teardown that can lead to a use-after-free of ub->ub_disk: 1. ublk_ctrl_start_dev() schedules partition_scan_work after add_disk() 2. ublk_stop_dev() calls ublk_stop_dev_unlocked() which does: - del_gendisk(ub->ub_disk) - ublk_detach_disk() sets ub->ub_disk = NULL - put_disk() which may free the disk 3. The worker ublk_partition_scan_work() then dereferences ub->ub_disk leading to UAF Fix this by using ublk_get_disk()/ublk_put_disk() in the worker to hold a reference to the disk during the partition scan. The spinlock in ublk_get_disk() synchronizes with ublk_detach_disk() ensuring the worker either gets a valid reference or sees NULL and exits early. Also change flush_work() to cancel_work_sync() to avoid running the partition scan work unnecessarily when the disk is already detached. Fixes: 7fc4da6 ("ublk: scan partition in async way") Reported-by: Ruikai Peng <ruikai@pwno.io> Signed-off-by: Ming Lei <ming.lei@redhat.com>
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Upstream branch: 623fb99 |
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Pull request for series with
subject: ublk: fix use-after-free in ublk_partition_scan_work
version: 1
url: https://patchwork.kernel.org/project/linux-block/list/?series=1040442