linux-kernel - Re: [PATCHv3 1/8] powerpc/vdso: unify return paths in setup_additional

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]

Date:   Tue, 08 Nov 2016 11:10:30 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Dmitry Safonov <dsafonov@...tuozzo.com>,
        linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <dsafonov@...tuozzo.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Andy Lutomirski <luto@...capital.net>,
        Oleg Nesterov <oleg@...hat.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-mm@...ck.org
Subject: Re: [PATCHv3 1/8] powerpc/vdso: unify return paths in setup_additional_pages

Hi Dmitry,

Thanks for the patches.

Dmitry Safonov <dsafonov@...tuozzo.com> writes:
> Impact: cleanup

I'm not a fan of these "Impact" lines, especially when they're not
correct, ie. this is not a cleanup, a cleanup doesn't change logic.

> Rename `rc' variable which doesn't seems to mean anything into
> kernel-known `ret'.

'rc' means "Return Code", it's fairly common. I see at least ~8500
"int rc" declarations in the kernel.

Please don't rename variables and change logic in one patch.

> Combine two function returns into one as it's
> also easier to read.
>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-mm@...ck.org
> Signed-off-by: Dmitry Safonov <dsafonov@...tuozzo.com>
> ---
>  arch/powerpc/kernel/vdso.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
> index 4111d30badfa..4ffb82a2d9e9 100644
> --- a/arch/powerpc/kernel/vdso.c
> +++ b/arch/powerpc/kernel/vdso.c
> @@ -154,7 +154,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>  	struct page **vdso_pagelist;
>  	unsigned long vdso_pages;
>  	unsigned long vdso_base;
> -	int rc;
> +	int ret = 0;
  
Please don't initialise return codes in the declaration, it prevents the
compiler from warning you if you forget to initialise it in a
particular path.

AFAICS you never even use the default value either.

>  	if (!vdso_ready)
>  		return 0;
> @@ -203,8 +203,8 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>  				      ((VDSO_ALIGNMENT - 1) & PAGE_MASK),
>  				      0, 0);
>  	if (IS_ERR_VALUE(vdso_base)) {
> -		rc = vdso_base;
> -		goto fail_mmapsem;
> +		ret = vdso_base;
> +		goto out_up_mmap_sem;
>  	}
>  
>  	/* Add required alignment. */
> @@ -227,21 +227,16 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>  	 * It's fine to use that for setting breakpoints in the vDSO code
>  	 * pages though.
>  	 */
> -	rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
> +	ret = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
>  				     VM_READ|VM_EXEC|
>  				     VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
>  				     vdso_pagelist);
> -	if (rc) {
> +	if (ret)
>  		current->mm->context.vdso_base = 0;
> -		goto fail_mmapsem;
> -	}
> -
> -	up_write(&mm->mmap_sem);
> -	return 0;
>  
> - fail_mmapsem:
> +out_up_mmap_sem:
>  	up_write(&mm->mmap_sem);
> -	return rc;
> +	return ret;
>  }


If you strip out the variable renames then I think that change would be
OK.

cheers