linux-kernel - Re: [PATCH 04/18] mm, aout: handle vm

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Message-ID: <56E29ECA.5050809@suse.cz>
Date:	Fri, 11 Mar 2016 11:32:42 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Michal Hocko <mhocko@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Alex Deucher <alexander.deucher@....com>,
	Alex Thorlton <athorlton@....com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Christian König <christian.koenig@....com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Davidlohr Bueso <dave@...olabs.net>,
	David Rientjes <rientjes@...gle.com>,
	"H . Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	linux-arch@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Cermak <petrcermak@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michal Hocko <mhocko@...e.com>, Ingo Molnar <mingo@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 04/18] mm, aout: handle vm_brk failures

On 02/29/2016 02:26 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
>
> vm_brk is allowed to fail but load_aout_binary simply ignores the error
> and happily continues. I haven't noticed any problem from that in real
> life but later patches will make the failure more likely because
> vm_brk will become killable (resp. mmap_sem for write waiting will become
> killable) so we should be more careful now.
>
> The error handling should be quite straightforward because there are
> calls to vm_mmap which check the error properly already. The only
> notable exception is set_brk which is called after beyond_if label.
> But nothing indicates that we cannot move it above set_binfmt as the two
> do not depend on each other and fail before we do set_binfmt and alter
> reference counting.
>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked--by: Vlastimil Babka <vbabka@...e.cz>

[...]

> @@ -378,7 +381,9 @@ static int load_aout_library(struct file *file)
>   			       "N_TXTOFF is not page aligned. Please convert library: %pD\n",
>   			       file);
>   		}
> -		vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
> +		retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
> +		if (IS_ERR_VALUE(retval))
> +			goto out;
>   		

You could have removed the extra whitespace on the line above, which my vim so 
prominently highlights :)

>   		read_code(file, start_addr, N_TXTOFF(ex),
>   			  ex.a_text + ex.a_data);
>