linux-kernel - Re: [PATCH -next V8 06/14] riscv: convert to generic entry

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJF2gTQwkPgafMxJ8YxH-kCsyT82bTr_a2hBJ1Pido7SvN+o2A@mail.gmail.com>
Date:   Mon, 28 Nov 2022 10:42:44 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Ben Hutchings <ben@...adent.org.uk>
Cc:     arnd@...db.de, palmer@...osinc.com, tglx@...utronix.de,
        peterz@...radead.org, luto@...nel.org, conor.dooley@...rochip.com,
        heiko@...ech.de, jszhang@...nel.org, lazyparser@...il.com,
        falcon@...ylab.org, chenhuacai@...nel.org, apatel@...tanamicro.com,
        atishp@...shpatra.org, palmer@...belt.com,
        paul.walmsley@...ive.com, mark.rutland@....com,
        zouyipeng@...wei.com, bigeasy@...utronix.de,
        David.Laight@...lab.com, chenzhongjin@...wei.com,
        greentime.hu@...ive.com, andy.chiu@...ive.com,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH -next V8 06/14] riscv: convert to generic entry

On Mon, Nov 28, 2022 at 12:26 AM Ben Hutchings <ben@...adent.org.uk> wrote:
>
> On Thu, 2022-11-03 at 03:50 -0400, guoren@...nel.org wrote:
> [...]
> > --- a/arch/riscv/kernel/sys_riscv.c
> > +++ b/arch/riscv/kernel/sys_riscv.c
> [...]
> > +asmlinkage void do_sys_ecall_u(struct pt_regs *regs)
> > +{
> > +     syscall_t syscall;
> > +     ulong nr = regs->a7;
> > +
> > +     regs->epc += 4;
> > +     regs->orig_a0 = regs->a0;
> > +     regs->a0 = -ENOSYS;
> > +
> > +     nr = syscall_enter_from_user_mode(regs, nr);
> > +#ifdef CONFIG_COMPAT
> > +     if ((regs->status & SR_UXL) == SR_UXL_32)
> > +             syscall = compat_sys_call_table[nr];
> > +     else
> > +#endif
> > +             syscall = sys_call_table[nr];
> > +
> > +     if (nr < NR_syscalls)
>
> This bounds check needs to be done before indexing the system call
> table, not after.
Yes, you are right. That would cause a wrong pointer bug. Here is the
new version:

asmlinkage void do_sys_ecall_u(struct pt_regs *regs)
{
        syscall_t syscall;
        ulong nr = regs->a7;

        regs->epc += 4;
        regs->orig_a0 = regs->a0;
        regs->a0 = -ENOSYS;

        nr = syscall_enter_from_user_mode(regs, nr);

        if (nr < NR_syscalls) {
#ifdef CONFIG_COMPAT
                if ((regs->status & SR_UXL) == SR_UXL_32)
                        syscall = compat_sys_call_table[nr];
                else
#endif
                        syscall = sys_call_table[nr];

                regs->a0 = syscall(regs->orig_a0, regs->a1, regs->a2,
                                   regs->a3, regs->a4, regs->a5, regs->a6);
        }
        syscall_exit_to_user_mode(regs);
}

>
> Ben.
>
> > +             regs->a0 = syscall(regs->orig_a0, regs->a1, regs->a2,
> > +                                regs->a3, regs->a4, regs->a5, regs->a6);
> > +     syscall_exit_to_user_mode(regs);
> > +}
> [...]
>
> --
> Ben Hutchings
> This sentence contradicts itself - no actually it doesn't.



-- 
Best Regards
 Guo Ren