linux-kernel - [PATCH] Fix kfree bug in sendmsg and recvmsg

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Message-ID: <20160217163805.GA15781@zipoli.ccur.com>
Date:	Wed, 17 Feb 2016 11:38:05 -0500
From:	Joe Korty <joe.korty@...r.com>
To:	"David S. Miller" <davem@...emloft.net>,
	Alexander Viro <viro@...iv.linux.org.uk>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] Fix kfree bug in sendmsg and recvmsg

Fix kfree bug in recvmsg and sendmsg.

We cannot kfree(iov) when iov points to an array on the
stack, as that has the potential of corrupting memory.

So re-introduce the if-stmt that used to protect kfree
from this condition, code that was removed as part of
a larger set of changes made by git commit da184284.

Signed-off-by: Joe Korty <joe.korty@...r.com>

Index: b/net/socket.c
===================================================================
--- a/net/socket.c
+++ b/net/socket.c
@@ -1960,7 +1960,8 @@ out_freectl:
 	if (ctl_buf != ctl)
 		sock_kfree_s(sock->sk, ctl_buf, ctl_len);
 out_freeiov:
-	kfree(iov);
+	if (iov != iovstack)
+		kfree(iov);
 	return err;
 }
 
@@ -2125,7 +2126,8 @@ static int ___sys_recvmsg(struct socket 
 	err = len;
 
 out_freeiov:
-	kfree(iov);
+	if (iov != iovstack)
+		kfree(iov);
 	return err;
 }