linux-kernel - Re: [PATCH v2] fs, elf: don't complain MAP_FIXED

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Date:   Thu, 19 Apr 2018 07:57:54 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     akpm@...ux-foundation.org, avagin@...nvz.org,
        khalid.aziz@...cle.com, mpe@...erman.id.au, keescook@...omium.org,
        abdhalee@...ux.vnet.ibm.com, joel@....id.au,
        khandual@...ux.vnet.ibm.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] fs, elf: don't complain MAP_FIXED_NOREPLACE unless
 -EEXIST error.

On Wed 18-04-18 23:07:12, Tetsuo Handa wrote:
> >From 3f396857d23d4bf1fac4d4332316b5ba0af6d2f9 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Date: Wed, 18 Apr 2018 23:00:53 +0900
> Subject: [PATCH v2] fs, elf: don't complain MAP_FIXED_NOREPLACE unless -EEXIST error.
> 
> Commit 4ed28639519c7bad ("fs, elf: drop MAP_FIXED usage from elf_map") is
> printing spurious messages under memory pressure due to map_addr == -ENOMEM.
> 
>  9794 (a.out): Uhuuh, elf segment at 00007f2e34738000(fffffffffffffff4) requested but the memory is mapped already
>  14104 (a.out): Uhuuh, elf segment at 00007f34fd76c000(fffffffffffffff4) requested but the memory is mapped already
>  16843 (a.out): Uhuuh, elf segment at 00007f930ecc7000(fffffffffffffff4) requested but the memory is mapped already
> 
> Complain only if -EEXIST, and use %px for printing the address.
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Acked-by: Michal Hocko <mhocko@...e.com>
> Cc: Andrei Vagin <avagin@...nvz.org>
> Cc: Khalid Aziz <khalid.aziz@...cle.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Abdul Haleem <abdhalee@...ux.vnet.ibm.com>
> Cc: Joel Stanley <joel@....id.au>
> Cc: Anshuman Khandual <khandual@...ux.vnet.ibm.com>

Thanks!

> ---
>  fs/binfmt_elf.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 41e0418..4ad6f66 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -377,10 +377,10 @@ static unsigned long elf_map(struct file *filep, unsigned long addr,
>  	} else
>  		map_addr = vm_mmap(filep, addr, size, prot, type, off);
>  
> -	if ((type & MAP_FIXED_NOREPLACE) && BAD_ADDR(map_addr))
> -		pr_info("%d (%s): Uhuuh, elf segment at %p requested but the memory is mapped already\n",
> -				task_pid_nr(current), current->comm,
> -				(void *)addr);
> +	if ((type & MAP_FIXED_NOREPLACE) &&
> +	    PTR_ERR((void *)map_addr) == -EEXIST)
> +		pr_info("%d (%s): Uhuuh, elf segment at %px requested but the memory is mapped already\n",
> +			task_pid_nr(current), current->comm, (void *)addr);
>  
>  	return(map_addr);
>  }
> -- 
> 1.8.3.1

-- 
Michal Hocko
SUSE Labs