diff mbox series

[2/2] riscv: fix syscall_{get,set}_arguments

Message ID 20181206150156.28210-3-david.abdurachmanov@gmail.com (mailing list archive)
State New, archived
Headers show
Series riscv: add support for SECCOMP and SECCOMP_FILTER | expand

Commit Message

David Abdurachmanov Dec. 6, 2018, 3:01 p.m. UTC 
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.

Signed-off-by: David Abdurachmanov <david.abdurachmanov@gmail.com>
---
 arch/riscv/include/asm/syscall.h | 42 ++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 10 deletions(-)

Comments

Kees Cook Dec. 6, 2018, 4:48 p.m. UTC | #1 
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. :)

-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, &regs->a1 + i * sizeof(regs->a1), n * sizeof(args[0]));
> +
> +       memcpy(args, &regs->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(&regs->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(&regs->a0 + i, args, n * sizeof(args[0]));
>  }
>
>  static inline int syscall_get_arch(void)
> --
> 2.19.2
>
David Abdurachmanov Dec. 6, 2018, 5:13 p.m. UTC | #2 
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, &regs->a1 + i * sizeof(regs->a1), n * sizeof(args[0]));
> > +
> > +       memcpy(args, &regs->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(&regs->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(&regs->a0 + i, args, n * sizeof(args[0]));
> >  }
> >
> >  static inline int syscall_get_arch(void)
> > --
> > 2.19.2
> >
>
>
> --
> Kees Cook
diff mbox series

Patch

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, &regs->a1 + i * sizeof(regs->a1), n * sizeof(args[0]));
+
+	memcpy(args, &regs->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(&regs->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(&regs->a0 + i, args, n * sizeof(args[0]));
 }
 
 static inline int syscall_get_arch(void)