Re: [PATCH 1/2] fs/proc: do_task_stat: Fix ESP not readable during coredump

[Thomas Gleixner <tglx@linutronix.de>]

On Wed, Nov 06 2024 at 10:22, Nam Cao wrote:
> Commit 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in
> /proc/PID/stat") disabled stack pointer reading, because it is generally
> dangerous to do so.
>
> Commit fd7d56270b52 ("fs/proc: Report eip/esp in /prod/PID/stat for
> coredumping") made an exception for coredumping thread, because for this
> case it is safe.
>
> The exception was later extended to all threads in a coredumping process by
> commit cb8f381f1613 ("fs/proc/array.c: allow reporting eip/esp for all
> coredumping threads").
>
> The above two commits determine if a task is core dumping by checking the
> PF_EXITING and PF_DUMPCORE flags.
>
> However, commit 92307383082d ("coredump:  Don't perform any cleanups before
> dumping core") moved coredump to happen earlier and before PF_EXITING is
> set. Thus, the check of the PF_EXITING flag no longer works.
>
> Instead, use task->signal->core_state to determine if coredump is
> happening. This pointer is set at the beginning of coredump and is cleared
> once coredump is done. Thus, while this pointer is not NULL, it is safe to
> read ESP.
>
> Fixes: 92307383082d ("coredump:  Don't perform any cleanups before dumping core")

Can we please make progress with that? It's a user space visible change
which causes a regression in core dumper tools.

Thanks,

        tglx