]> www.infradead.org Git - users/jedix/linux-maple.git/commit
kfence: avoid stalling work queue task without allocations
authorMarco Elver <elver@google.com>
Thu, 31 Dec 2020 22:04:32 +0000 (22:04 +0000)
committerJohannes Weiner <hannes@cmpxchg.org>
Thu, 31 Dec 2020 22:04:32 +0000 (22:04 +0000)
commitb877f1c9d08a7e6831791832cc64c8cd97200fb6
tree78cf88082879de215cc43d53564558656411ee35
parent8a0fc50917eefd6d0ffb3e0c6fd61a496754c662
kfence: avoid stalling work queue task without allocations

To toggle the allocation gates, we set up a delayed work that calls
toggle_allocation_gate().  Here we use wait_event() to await an allocation
and subsequently disable the static branch again.  However, if the kernel
has stopped doing allocations entirely, we'd wait indefinitely, and stall
the worker task.  This may also result in the appropriate warnings if
CONFIG_DETECT_HUNG_TASK=y.

Therefore, introduce a 1 second timeout and use wait_event_timeout().  If
the timeout is reached, the static branch is disabled and a new delayed
work is scheduled to try setting up an allocation at a later time.

Note that, this scenario is very unlikely during normal workloads once the
kernel has booted and user space tasks are running.  It can, however,
happen during early boot after KFENCE has been enabled, when e.g.  running
tests that do not result in any allocations.

Link: https://lkml.kernel.org/r/CADYN=9J0DQhizAGB0-jz4HOBBh+05kMBXb4c0cXMS7Qi5NAJiw@mail.gmail.com
Link: https://lkml.kernel.org/r/20201110135320.3309507-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: SeongJae Park <sjpark@amazon.de>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/kfence/core.c