Messages in this thread Patch in this message | | | From | "Eric W. Biederman" <> | Date | Mon, 17 Jan 2022 12:46:48 -0600 | Subject | io_uring truncating coredumps |
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Subject updated to reflect the current discussion.
> Linus Torvalds <torvalds@linux-foundation.org> writes:
> But I really think it's wrong. > > You're trying to work around a problem the wrong way around. If a task > is dead, and is dumping core, then signals just shouldn't matter in > the first place, and thus the whole "TASK_INTERRUPTIBLE vs > TASK_UNINTERRUPTIBLE" really shouldn't be an issue. The fact that it > is an issue means there's something wrong in signaling, not in the > pipe code. > > So I really think that's where the fix should be - on the signal delivery side.
Thinking about it from the perspective of not delivering the wake-ups fixing io_uring and coredumps in a non-hacky way looks comparatively simple. The function task_work_add just needs to not wake anything up after a process has started dying.
Something like the patch below.
The only tricky part I can see is making certain there are not any races between task_work_add and do_coredump depending on task_work_add not causing signal_pending to return true.
diff --git a/kernel/task_work.c b/kernel/task_work.c index fad745c59234..5f941e377268 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -44,6 +44,9 @@ int task_work_add(struct task_struct *task, struct callback_head *work, work->next = head; } while (cmpxchg(&task->task_works, head, work) != head); + if (notify && (task->signal->flags & SIGNAL_GROUP_EXIT)) + return 0; + switch (notify) { case TWA_NONE: break; Eric
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