linux-kernel - Re: [PATCH] mm: respect arch_dup

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Message-ID: <20180823085714.GY29735@dhcp22.suse.cz>
Date:   Thu, 23 Aug 2018 10:57:14 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Nadav Amit <namit@...are.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] mm: respect arch_dup_mmap() return value

On Wed 22-08-18 22:12:29, Nadav Amit wrote:
> Commit d70f2a14b72a4 ("include/linux/sched/mm.h: uninline
> mmdrop_async(), etc") ignored the return value of arch_dup_mmap(). As a
> result, on x86, a failure to duplicate the LDT (e.g., due to memory
> allocation error), would leave the duplicated memory mapping in an
> inconsistent state.
> 
> Fix by regarding the return value, as it was before the change.

Ohh, well spotted! I have a vague recollection I didn't really like the
patch. For other reasons. I didn't get to review it properly back then
because I didn't have much time and I didn't have a high motivation
because I simple disagreed with the patch.

> Fixes: d70f2a14b72a4 ("include/linux/sched/mm.h: uninline mmdrop_async(), etc")
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: stable@...r.kernel.org
> Signed-off-by: Nadav Amit <namit@...are.com>

Acked-by: Michal Hocko <mhocko@...e.com>

Thanks!

> ---
>  kernel/fork.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 1b27babc4c78..4527d1d331de 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -549,8 +549,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
>  			goto out;
>  	}
>  	/* a new mm has just been created */
> -	arch_dup_mmap(oldmm, mm);
> -	retval = 0;
> +	retval = arch_dup_mmap(oldmm, mm);
>  out:
>  	up_write(&mm->mmap_sem);
>  	flush_tlb_mm(oldmm);
> -- 
> 2.17.1
> 

-- 
Michal Hocko
SUSE Labs