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From:   Andreas Schwab <schwab@suse.de>
To:     David Abdurachmanov <david.abdurachmanov@gmail.com>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        David Abdurachmanov <david.abdurachmanov@sifive.com>,
        Kees Cook <keescook@chromium.org>,
        Anup Patel <Anup.Patel@wdc.com>,
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        Valentin Schneider <valentin.schneider@arm.com>,
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        linux-riscv <linux-riscv@lists.infradead.org>,
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Subject: Re: [PATCH] riscv: reject invalid syscalls below -1
References: <20191218084757.904971-1-david.abdurachmanov@sifive.com>
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Date:   Wed, 18 Dec 2019 11:35:26 +0100
In-Reply-To: <CAEn-LTojXuAbY31nReCsbE=7Q9PkuKexAttTc+35ZFn7SLG-_w@mail.gmail.com>
        (David Abdurachmanov's message of "Wed, 18 Dec 2019 12:06:57 +0200")
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On Dez 18 2019, David Abdurachmanov wrote:

> On Wed, Dec 18, 2019 at 11:46 AM Andreas Schwab <schwab@suse.de> wrote:
>>
>> On Dez 18 2019, David Abdurachmanov wrote:
>>
>> > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
>> > index a1349ca64669..e163b7b64c86 100644
>> > --- a/arch/riscv/kernel/entry.S
>> > +++ b/arch/riscv/kernel/entry.S
>> > @@ -246,6 +246,7 @@ check_syscall_nr:
>> >        */
>> >       li t1, -1
>> >       beq a7, t1, ret_from_syscall_rejected
>> > +     blt a7, t1, 1f
>>
>> How about using bgeu instead in the preceding check?
>
> The syscall number could be -1 if tracer rejected it.

So check for -1 first, then for out-of-range?

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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