linux-kernel - Re: [PATCH v2 3/3] audit: Use syscall_get_return_value to get syscall return code in audit_syscall

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Date:   Mon, 10 May 2021 18:38:53 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     He Zhe <zhe.he@...driver.com>
Cc:     oleg@...hat.com, catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        Eric Paris <eparis@...hat.com>, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] audit: Use syscall_get_return_value to get syscall
 return code in audit_syscall_exit

On Fri, Apr 23, 2021 at 6:36 AM He Zhe <zhe.he@...driver.com> wrote:
>
> regs_return_value for some architectures like arm64 simply retrieve
> register value from pt_regs without sign extension in 32-bit compatible
> case and cause audit to have false syscall return code. For example,
> 32-bit -13 would be treated as 4294967283 below.
>
> type=SYSCALL msg=audit(1611110715.887:582): arch=40000028 syscall=322
> success=yes exit=4294967283
>
> We just added proper sign extension in syscall_get_return_value which
> should be used instead.
>
> Signed-off-by: He Zhe <zhe.he@...driver.com>
> ---
> v1 to v2: No change
>
>  include/linux/audit.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Perhaps I missed it but did you address the compile error that was
found by the kernel test robot?

Regardless, one comment inline below ...

> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 82b7c1116a85..135adbe22c19 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -334,7 +334,7 @@ static inline void audit_syscall_exit(void *pt_regs)
>  {
>         if (unlikely(audit_context())) {
>                 int success = is_syscall_success(pt_regs);

Since we are shifting to use syscall_get_return_value() below, would
it also make sense to shift to using syscall_get_error() here instead
of is_syscall_success()?

> -               long return_code = regs_return_value(pt_regs);
> +               long return_code = syscall_get_return_value(current, pt_regs);
>
>                 __audit_syscall_exit(success, return_code);
>         }

-- 
paul moore
www.paul-moore.com