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authorPaolo Valente <paolo.valente@linaro.org>2019-11-14 10:33:11 +0100
committerJens Axboe <axboe@kernel.dk>2019-11-14 07:00:54 -0700
commit478de3380c1c7dbb0f65f545ee0185848413f3fe (patch)
tree11ad17255fb0d30ea1cc2139f0017af571d6496c /block/blk-iocost.c
parent5e559561a8d7e6d4adfce6aa8fbf3daa3dec1577 (diff)
downloadlinux-478de3380c1c7dbb0f65f545ee0185848413f3fe.tar.bz2
block, bfq: deschedule empty bfq_queues not referred by any process
Since commit 3726112ec731 ("block, bfq: re-schedule empty queues if they deserve I/O plugging"), to prevent the service guarantees of a bfq_queue from being violated, the bfq_queue may be left busy, i.e., scheduled for service, even if empty (see comments in __bfq_bfqq_expire() for details). But, if no process will send requests to the bfq_queue any longer, then there is no point in keeping the bfq_queue scheduled for service. In addition, keeping the bfq_queue scheduled for service, but with no process reference any longer, may cause the bfq_queue to be freed when descheduled from service. But this is assumed to never happen, and causes a UAF if it happens. This, in turn, caused crashes [1, 2]. This commit fixes this issue by descheduling an empty bfq_queue when it remains with not process reference. [1] https://bugzilla.redhat.com/show_bug.cgi?id=1767539 [2] https://bugzilla.kernel.org/show_bug.cgi?id=205447 Fixes: 3726112ec731 ("block, bfq: re-schedule empty queues if they deserve I/O plugging") Reported-by: Chris Evich <cevich@redhat.com> Reported-by: Patrick Dung <patdung100@gmail.com> Reported-by: Thorsten Schubert <tschubert@bafh.org> Tested-by: Thorsten Schubert <tschubert@bafh.org> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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