linux-kernel - RE: [PATCH] sctp: use GFP_USER for user-controlled kmalloc

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CBDF85D@AcuExch.aculab.com>
Date:	Tue, 1 Dec 2015 10:46:11 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Marcelo Ricardo Leitner' <marcelo.leitner@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	"linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
	Vlad Yasevich <vyasevich@...il.com>,
	Neil Horman <nhorman@...driver.com>,
	"daniel@...earbox.net" <daniel@...earbox.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"syzkaller@...glegroups.com" <syzkaller@...glegroups.com>,
	"dvyukov@...gle.com" <dvyukov@...gle.com>,
	"kcc@...gle.com" <kcc@...gle.com>,
	"glider@...gle.com" <glider@...gle.com>,
	"sasha.levin@...cle.com" <sasha.levin@...cle.com>,
	"edumazet@...gle.com" <edumazet@...gle.com>
Subject: RE: [PATCH] sctp: use GFP_USER for user-controlled kmalloc

From: Marcelo Ricardo Leitner
> Sent: 30 November 2015 16:33
> Dmitry Vyukov reported that the user could trigger a kernel warning by
> using a large len value for getsockopt SCTP_GET_LOCAL_ADDRS, as that
> value directly affects the value used as a kmalloc() parameter.
> 
> This patch thus switches the allocation flags from all user-controllable
> kmalloc size to GFP_USER to put some more restrictions on it and also
> disables the warn, as they are not necessary.

ISTM that the code should put some 'sanity limit' on that
size before allocating the kernel buffer.

	David

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