linux-kernel - Re: [PATCH 2/3] m68k: update ->thread.esp0 before calling syscall_trace() in ret_from

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Message-ID: <a0dad440-03bd-cac6-6eee-22a1fdd2f825@gmail.com>
Date:   Thu, 16 Sep 2021 10:19:31 +1200
From:   Michael Schmitz <schmitzmic@...il.com>
To:     Al Viro <viro@...iv.linux.org.uk>, linux-m68k@...ts.linux-m68k.org
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] m68k: update ->thread.esp0 before calling
 syscall_trace() in ret_from_signal

Hi Al,

On 26/07/21 5:19 am, Al Viro wrote:
> We get there when sigreturn has performed obscene acts on kernel stack;
> in particular, the location of pt_regs has shifted.  We are about to call
> syscall_trace(), which might stop for tracer.  If that happens, we'd better
> have task_pt_regs() returning correct result...
>
> Fucked-up-by: Al Viro <viro@...iv.linux.org.uk>
> Fixes: bd6f56a75bb2 ("m68k: Missing syscall_trace() on sigreturn")
> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>

Looking good also, and should go to -stable.

Tested-by: Michael Schmitz <schmitzmic@...il.com>

Reviewed-by: Michael Schmitz <schmitzmic@...il.com>

> ---
>   arch/m68k/kernel/entry.S | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S
> index 9dd76fbb7c6b..ff9e842cec0f 100644
> --- a/arch/m68k/kernel/entry.S
> +++ b/arch/m68k/kernel/entry.S
> @@ -186,6 +186,8 @@ ENTRY(ret_from_signal)
>   	movel	%curptr@(TASK_STACK),%a1
>   	tstb	%a1@(TINFO_FLAGS+2)
>   	jge	1f
> +	lea	%sp@(SWITCH_STACK_SIZE),%a1
> +	movel	%a1,%curptr@(TASK_THREAD+THREAD_ESP0)
>   	jbsr	syscall_trace
>   1:	RESTORE_SWITCH_STACK
>   	addql	#4,%sp