Subject: [Bug 214913] [xfstests generic/051] BUG: Kernel NULL pointer dereference on read at 0x00000108 NIP [c0000000000372e4] tm_cgpr_active+0x14/0x40

From: [email-masked]
Date: Mon, 12 Dec 2022 07:19:56 +0000

https://bugzilla.kernel.org/show_bug.cgi?id=214913

--- Comment #10 from [email-masked] ---
On Mon Dec 12, 2022 at 3:57 PM AEST,  wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=214913
>
> --- Comment #9 from Michael Ellerman ([email-masked]) ---
> I assume it's an io_uring IO worker.
>
> They're created via create_io_worker() -> create_io_thread().
>
> They pass a non-NULL `args->fn` to copy_process() -> copy_thread(), so we end
> up in the "kernel thread" branch of the if, which sets p->thread.regs = NULL.

Hmm, you might be right. These things are created with the memory and
thread  / signal context shared with the userspace process.

Still doesn't seem like they should be involved in core dumping though,
pt_regs would have no meaning even if we did set something there. How
best to catch these and filter them out of the core dump? Check for
PF_IO_WORKER in the coredump gathering?

Thanks,
Nick

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