linux-kernel - [PATCH 3.16.y-ckt 164/165] net: compat: Update get_compat_msghdr() to match copy_msghdr_from

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Message-Id: <1427292138-7021-165-git-send-email-luis.henriques@canonical.com>
Date:	Wed, 25 Mar 2015 14:02:17 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	"David S. Miller" <davem@...emloft.net>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 164/165] net: compat: Update get_compat_msghdr() to match copy_msghdr_from_user() behaviour

3.16.7-ckt9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Catalin Marinas <catalin.marinas@....com>

commit 91edd096e224941131f896b86838b1e59553696a upstream.

Commit db31c55a6fb2 (net: clamp ->msg_namelen instead of returning an
error) introduced the clamping of msg_namelen when the unsigned value
was larger than sizeof(struct sockaddr_storage). This caused a
msg_namelen of -1 to be valid. The native code was subsequently fixed by
commit dbb490b96584 (net: socket: error on a negative msg_namelen).

In addition, the native code sets msg_namelen to 0 when msg_name is
NULL. This was done in commit (6a2a2b3ae075 net:socket: set msg_namelen
to 0 if msg_name is passed as NULL in msghdr struct from userland) and
subsequently updated by 08adb7dabd48 (fold verify_iovec() into
copy_msghdr_from_user()).

This patch brings the get_compat_msghdr() in line with
copy_msghdr_from_user().

Fixes: db31c55a6fb2 (net: clamp ->msg_namelen instead of returning an error)
Cc: David S. Miller <davem@...emloft.net>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[ luis: backported to 3.16: used davem's backport to 3.14 ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 net/compat.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/compat.c b/net/compat.c
index c48930373e65..53e933eb78b8 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -71,6 +71,13 @@ int get_compat_msghdr(struct msghdr *kmsg, struct compat_msghdr __user *umsg)
 	    __get_user(kmsg->msg_controllen, &umsg->msg_controllen) ||
 	    __get_user(kmsg->msg_flags, &umsg->msg_flags))
 		return -EFAULT;
+
+	if (!tmp1)
+		kmsg->msg_namelen = 0;
+
+	if (kmsg->msg_namelen < 0)
+		return -EINVAL;
+
 	if (kmsg->msg_namelen > sizeof(struct sockaddr_storage))
 		kmsg->msg_namelen = sizeof(struct sockaddr_storage);
 	kmsg->msg_name = compat_ptr(tmp1);
--
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