linux-kernel - Re: [PATCH 1/4] ipc/shm.c: check for ulong overflows in shmat

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Date:	Wed, 23 Apr 2014 06:58:15 +0200
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	Manfred Spraul <manfred@...orfullife.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
CC:	mtk.manpages@...il.com, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	gthelen@...gle.com, aswin@...com, linux-mm@...ck.org
Subject: Re: [PATCH 1/4] ipc/shm.c: check for ulong overflows in shmat

On 04/21/2014 04:26 PM, Manfred Spraul wrote:
> find_vma_intersection does not work as intended if addr+size overflows.
> The patch adds a manual check before the call to find_vma_intersection.
> 
> Signed-off-by: Manfred Spraul <manfred@...orfullife.com>
> ---
>  ipc/shm.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/ipc/shm.c b/ipc/shm.c
> index 7645961..382e2fb 100644
> --- a/ipc/shm.c
> +++ b/ipc/shm.c
> @@ -1160,6 +1160,9 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
>  	down_write(&current->mm->mmap_sem);
>  	if (addr && !(shmflg & SHM_REMAP)) {
>  		err = -EINVAL;
> +		if (addr + size < addr)
> +			goto invalid;
> +
>  		if (find_vma_intersection(current->mm, addr, addr + size))
>  			goto invalid;
>  		/*
> 

Acked-by: Michael Kerrisk <mtk.manpages@...il.com>

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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