netdev - [PATCH] sctp: use GFP_USER for user-controlled kmalloc

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Date:	Mon, 30 Nov 2015 14:32:54 -0200
From:	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:	netdev@...r.kernel.org
Cc:	linux-sctp@...r.kernel.org, Vlad Yasevich <vyasevich@...il.com>,
	Neil Horman <nhorman@...driver.com>, daniel@...earbox.net,
	linux-kernel@...r.kernel.org, davem@...emloft.net,
	syzkaller@...glegroups.com, dvyukov@...gle.com, kcc@...gle.com,
	glider@...gle.com, sasha.levin@...cle.com, edumazet@...gle.com
Subject: [PATCH] sctp: use GFP_USER for user-controlled kmalloc

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.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
---
 net/sctp/socket.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 897c01c029cab3d5805cc56b0964c70e06f4143a..676b3bb092e16848fd1c822e1c999af4a2ef198d 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -972,7 +972,7 @@ static int sctp_setsockopt_bindx(struct sock *sk,
 		return -EFAULT;
 
 	/* Alloc space for the address array in kernel memory.  */
-	kaddrs = kmalloc(addrs_size, GFP_KERNEL);
+	kaddrs = kmalloc(addrs_size, GFP_USER | __GFP_NOWARN);
 	if (unlikely(!kaddrs))
 		return -ENOMEM;
 
@@ -4928,7 +4928,7 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 	to = optval + offsetof(struct sctp_getaddrs, addrs);
 	space_left = len - offsetof(struct sctp_getaddrs, addrs);
 
-	addrs = kmalloc(space_left, GFP_KERNEL);
+	addrs = kmalloc(space_left, GFP_USER | __GFP_NOWARN);
 	if (!addrs)
 		return -ENOMEM;
 
-- 
2.5.0

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