linux-kernel - Re: [PATCH 1/3] arm/syscalls: Move address limit check in loop

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Date:   Mon, 24 Jul 2017 10:07:09 -0700
From:   Thomas Garnier <thgarnie@...gle.com>
To:     Russell King <linux@...linux.org.uk>,
        Thomas Garnier <thgarnie@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Dave Martin <Dave.Martin@....com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Pratyush Anand <panand@...hat.com>,
        Leonard Crestez <leonard.crestez@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 1/3] arm/syscalls: Move address limit check in loop

On Wed, Jul 19, 2017 at 10:58 AM, Thomas Garnier <thgarnie@...gle.com> wrote:
> The work pending loop can call set_fs after addr_limit_user_check
> removed the _TIF_FSCHECK flag. To prevent the infinite loop, move
> the addr_limit_user_check call at the beginning of the loop.
>
> Fixes: 73ac5d6a2b6a ("arm/syscalls: Check address limit on user-mode return")
> Reported-by: Leonard Crestez <leonard.crestez@....com>
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>

Any comments on this patch set?

> ---
>  arch/arm/kernel/signal.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
> index 3a48b54c6405..f4574287d14b 100644
> --- a/arch/arm/kernel/signal.c
> +++ b/arch/arm/kernel/signal.c
> @@ -573,10 +573,10 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
>          */
>         trace_hardirqs_off();
>
> -       /* Check valid user FS if needed */
> -       addr_limit_user_check();
> -
>         do {
> +               /* Check valid user FS if needed */
> +               addr_limit_user_check();
> +
>                 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
>                         schedule();
>                 } else {
> --
> 2.14.0.rc0.284.gd933b75aa4-goog
>



-- 
Thomas