linux-kernel - RE: [PATCH 1/2] audit: Add syscall return code handling for compat task

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Message-ID: <e3e058cb2605482d9cfcb3466d680b71@AcuMS.aculab.com>
Date:   Wed, 14 Apr 2021 15:35:28 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'He Zhe' <zhe.he@...driver.com>,
        "paul@...l-moore.com" <paul@...l-moore.com>,
        "eparis@...hat.com" <eparis@...hat.com>,
        "linux-audit@...hat.com" <linux-audit@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] audit: Add syscall return code handling for compat
 task

From: He Zhe
> Sent: 14 April 2021 09:02
> 
> When 32-bit userspace application is running on 64-bit kernel, the 32-bit
> syscall return code would be changed from u32 to u64 in regs_return_value
> and then changed to s64. Hence the negative return code recorded by audit
> would end up being a big positive number like below.
> 
> type=SYSCALL msg=audit(1611110715.887:582): arch=40000028 syscall=322
> success=yes exit=4294967283
> 
> This patch forces the u32->s32->s64 for compat tasks.
> 
> Signed-off-by: He Zhe <zhe.he@...driver.com>
> ---
>  include/linux/audit.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 82b7c1116a85..32cb853f3029 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -334,7 +334,9 @@ static inline void audit_syscall_exit(void *pt_regs)
>  {
>  	if (unlikely(audit_context())) {
>  		int success = is_syscall_success(pt_regs);
> -		long return_code = regs_return_value(pt_regs);
> +		long return_code = is_compat_task() ?

Should that be is_compat_syscall() ?
A x86-64 process can make both types of 32bit system calls.

	David

> +			(s64)(s32)regs_return_value(pt_regs) :
> +			regs_return_value(pt_regs);
> 
>  		__audit_syscall_exit(success, return_code);
>  	}
> --
> 2.17.1

-
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