linux-kernel - Re: [PATCH v2 5/5] powerpc/signal: Use unsafe_copy_siginfo_to

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Message-ID: <87y28ex1ov.fsf@disp2133>
Date:   Thu, 02 Sep 2021 13:38:40 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 5/5] powerpc/signal: Use unsafe_copy_siginfo_to_user()

Christophe Leroy <christophe.leroy@...roup.eu> writes:

> Use unsafe_copy_siginfo_to_user() in order to do the copy
> within the user access block.
>
> On an mpc 8321 (book3s/32) the improvment is about 5% on a process
> sending a signal to itself.

Nacked-by: "Eric W. Biederman" <ebiederm@...ssion.com>

copy_siginfo_to_user is not the same as copy_siginfo_to_user32.

As in this patch breaks 32bit userspace on powerpc.


> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  arch/powerpc/kernel/signal_32.c | 13 ++++++-------
>  arch/powerpc/kernel/signal_64.c |  5 +----
>  2 files changed, 7 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
> index ff101e2b3bab..f9e16d108bc8 100644
> --- a/arch/powerpc/kernel/signal_32.c
> +++ b/arch/powerpc/kernel/signal_32.c
> @@ -710,12 +710,6 @@ static long restore_tm_user_regs(struct pt_regs *regs, struct mcontext __user *s
>  }
>  #endif
>  
> -#ifdef CONFIG_PPC64
> -
> -#define copy_siginfo_to_user	copy_siginfo_to_user32
> -
> -#endif /* CONFIG_PPC64 */
> -
>  /*
>   * Set up a signal frame for a "real-time" signal handler
>   * (one which gets siginfo).
> @@ -779,14 +773,19 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
>  		asm("dcbst %y0; sync; icbi %y0; sync" :: "Z" (mctx->mc_pad[0]));
>  	}
>  	unsafe_put_sigset_t(&frame->uc.uc_sigmask, oldset, failed);
> +#ifndef CONFIG_COMPAT
> +	unsafe_copy_siginfo_to_user(&frame->info, &ksig->info, failed);
> +#endif
>  
>  	/* create a stack frame for the caller of the handler */
>  	unsafe_put_user(regs->gpr[1], newsp, failed);
>  
>  	user_access_end();
>  
> -	if (copy_siginfo_to_user(&frame->info, &ksig->info))
> +#ifdef CONFIG_COMPAT
> +	if (copy_siginfo_to_user32(&frame->info, &ksig->info))
>  		goto badframe;
> +#endif
>  
>  	regs->link = tramp;
>  
> diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
> index 2cca6c8febe1..82b73fbd937d 100644
> --- a/arch/powerpc/kernel/signal_64.c
> +++ b/arch/powerpc/kernel/signal_64.c
> @@ -901,15 +901,12 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
>  	}
>  
>  	unsafe_copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set), badframe_block);
> +	unsafe_copy_siginfo_to_user(&frame->info, &ksig->info, badframe_block);
>  	/* Allocate a dummy caller frame for the signal handler. */
>  	unsafe_put_user(regs->gpr[1], newsp, badframe_block);
>  
>  	user_write_access_end();
>  
> -	/* Save the siginfo outside of the unsafe block. */
> -	if (copy_siginfo_to_user(&frame->info, &ksig->info))
> -		goto badframe;
> -
>  	/* Make sure signal handler doesn't get spurious FP exceptions */
>  	tsk->thread.fp_state.fpscr = 0;