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| /openbmc/qemu/util/ |
| H A D | async.c | f0f81002 Tue Jul 23 14:06:23 CDT 2019 Stefan Hajnoczi <stefanha@redhat.com> util/async: hold AioContext ref to prevent use-after-free
The tests/test-bdrv-drain /bdrv-drain/iothread/drain test case does the
following:
1. The preadv coroutine calls aio_bh_schedule_oneshot() and then yields.
2. The one-shot BH executes in another AioContext. All it does is call
aio_co_wakeup(preadv_co).
3. The preadv coroutine is re-entered and returns.
There is a race condition in aio_co_wake() where the preadv coroutine
returns and the test case destroys the preadv IOThread. aio_co_wake()
can still be running in the other AioContext and it performs an access
to the freed IOThread AioContext.
Here is the race in aio_co_schedule():
QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines,
co, co_scheduled_next);
<-- race: co may execute before we invoke qemu_bh_schedule()!
qemu_bh_schedule(ctx->co_schedule_bh);
So if co causes ctx to be freed then we're in trouble. Fix this problem
by holding a reference to ctx.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 20190723190623.21537-1-stefanha@redhat.com
Message-Id: <20190723190623.21537-1-stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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