From: David Abdurachmanov <david.abdurachmanov@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: aou@eecs.berkeley.edu, Will Drewry <wad@chromium.org>,
Palmer Dabbelt <palmer@sifive.com>,
linux-kernel@vger.kernel.org, luto@amacapital.net,
Green Hu <green.hu@gmail.com>,
linux-riscv@lists.infradead.org, deanbo422@gmail.com
Subject: Re: [PATCH 2/2] riscv: fix syscall_{get,set}_arguments
Date: Thu, 6 Dec 2018 18:13:52 +0100 [thread overview]
Message-ID: <CAEn-LTqOvegggVV8tWO5WUBQ5=8s0Li5xFBwokENQBf6_RLuAA@mail.gmail.com> (raw)
In-Reply-To: <CAGXu5jJT4wY9wgCF8gB+tjgH+YQps4eUDVwZoGY=GVmLMpLPxw@mail.gmail.com>
On Thu, Dec 6, 2018 at 5:49 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Dec 6, 2018 at 7:02 AM David Abdurachmanov
> <david.abdurachmanov@gmail.com> wrote:
> >
> > Testing with libseccomp master branch revealed that testcases with
> > filters on syscall arguments were failing due to wrong values. Seccomp
> > uses syscall_get_argumentsi() to copy syscall arguments, and there is a
> > bug in pointer arithmetics in memcpy() call.
> >
> > Two alternative implementation were tested: the one in this patch and
> > another one based on while-break loop. Both delivered the same results.
> >
> > This implementation is also used in arm, arm64 and nds32 arches.
>
> Minor nit: can you make this the first patch? That way seccomp works
> correctly from the point of introduction. :)
Ok. I will do it.
david
>
> -Kees
>
> >
> > Signed-off-by: David Abdurachmanov <david.abdurachmanov@gmail.com>
> > ---
> > arch/riscv/include/asm/syscall.h | 42 ++++++++++++++++++++++++--------
> > 1 file changed, 32 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
> > index bba3da6ef157..26ceb434a433 100644
> > --- a/arch/riscv/include/asm/syscall.h
> > +++ b/arch/riscv/include/asm/syscall.h
> > @@ -70,19 +70,32 @@ static inline void syscall_set_return_value(struct task_struct *task,
> > regs->a0 = (long) error ?: val;
> > }
> >
> > +#define SYSCALL_MAX_ARGS 6
> > +
> > static inline void syscall_get_arguments(struct task_struct *task,
> > struct pt_regs *regs,
> > unsigned int i, unsigned int n,
> > unsigned long *args)
> > {
> > - BUG_ON(i + n > 6);
> > + if (n == 0)
> > + return;
> > +
> > + if (i + n > SYSCALL_MAX_ARGS) {
> > + unsigned long *args_bad = args + SYSCALL_MAX_ARGS - i;
> > + unsigned int n_bad = n + i - SYSCALL_MAX_ARGS;
> > + pr_warning("%s called with max args %d, handling only %d\n",
> > + __func__, i + n, SYSCALL_MAX_ARGS);
> > + memset(args_bad, 0, n_bad * sizeof(args[0]));
> > + }
> > +
> > if (i == 0) {
> > args[0] = regs->orig_a0;
> > args++;
> > i++;
> > n--;
> > }
> > - memcpy(args, ®s->a1 + i * sizeof(regs->a1), n * sizeof(args[0]));
> > +
> > + memcpy(args, ®s->a0 + i, n * sizeof(args[0]));
> > }
> >
> > static inline void syscall_set_arguments(struct task_struct *task,
> > @@ -90,14 +103,23 @@ static inline void syscall_set_arguments(struct task_struct *task,
> > unsigned int i, unsigned int n,
> > const unsigned long *args)
> > {
> > - BUG_ON(i + n > 6);
> > - if (i == 0) {
> > - regs->orig_a0 = args[0];
> > - args++;
> > - i++;
> > - n--;
> > - }
> > - memcpy(®s->a1 + i * sizeof(regs->a1), args, n * sizeof(regs->a0));
> > + if (n == 0)
> > + return;
> > +
> > + if (i + n > SYSCALL_MAX_ARGS) {
> > + pr_warning("%s called with max args %d, handling only %d\n",
> > + __func__, i + n, SYSCALL_MAX_ARGS);
> > + n = SYSCALL_MAX_ARGS - i;
> > + }
> > +
> > + if (i == 0) {
> > + regs->orig_a0 = args[0];
> > + args++;
> > + i++;
> > + n--;
> > + }
> > +
> > + memcpy(®s->a0 + i, args, n * sizeof(args[0]));
> > }
> >
> > static inline int syscall_get_arch(void)
> > --
> > 2.19.2
> >
>
>
> --
> Kees Cook
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prev parent reply other threads:[~2018-12-06 17:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-06 15:01 [PATCH 0/2] riscv: add support for SECCOMP and SECCOMP_FILTER David Abdurachmanov
2018-12-06 15:01 ` [PATCH 1/2] riscv: add support for SECCOMP incl. filters David Abdurachmanov
2018-12-06 16:47 ` Kees Cook
2018-12-06 17:10 ` David Abdurachmanov
2018-12-06 16:51 ` Kees Cook
2018-12-06 17:11 ` David Abdurachmanov
2018-12-06 18:25 ` David Abdurachmanov
2018-12-06 18:32 ` Kees Cook
2018-12-06 17:06 ` Kees Cook
2018-12-06 17:12 ` David Abdurachmanov
2018-12-06 15:01 ` [PATCH 2/2] riscv: fix syscall_{get,set}_arguments David Abdurachmanov
2018-12-06 16:48 ` Kees Cook
2018-12-06 17:13 ` David Abdurachmanov [this message]
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