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Date:      Sun, 5 Jul 2020 10:57:28 +0000 (UTC)
From:      Edward Tomasz Napierala <trasz@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r362941 - head/sys/compat/linux
Message-ID:  <202007051057.065AvSaV085085@repo.freebsd.org>
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Author: trasz
Date: Sun Jul  5 10:57:28 2020
New Revision: 362941
URL: https://svnweb.freebsd.org/changeset/base/362941

Log:
  Fix Linux recvmsg(2) when msg_namelen returned is 0.  Previously
  it would fail with EINVAL, breaking some of the Python regression
  tests.
  
  While here, cap the user-controlled message length.
  
  Note that the code doesn't seem to be copying out the new length
  in either (success or failure) case. This will be addressed separately.
  
  Reviewed by:	kib
  MFC after:	2 weeks
  Sponsored by:	The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D25392

Modified:
  head/sys/compat/linux/linux_socket.c

Modified: head/sys/compat/linux/linux_socket.c
==============================================================================
--- head/sys/compat/linux/linux_socket.c	Sun Jul  5 06:51:39 2020	(r362940)
+++ head/sys/compat/linux/linux_socket.c	Sun Jul  5 10:57:28 2020	(r362941)
@@ -1196,11 +1196,14 @@ linux_recvmsg_common(struct thread *td, l_int s, struc
 	if (error != 0)
 		return (error);
 
-	if (msg->msg_name) {
+	if (msg->msg_name != NULL && msg->msg_namelen > 0) {
+		msg->msg_namelen = min(msg->msg_namelen, SOCK_MAXADDRLEN);
 		sa = malloc(msg->msg_namelen, M_SONAME, M_WAITOK);
 		msg->msg_name = sa;
-	} else
+	} else {
 		sa = NULL;
+		msg->msg_name = NULL;
+	}
 
 	uiov = msg->msg_iov;
 	msg->msg_iov = iov;
@@ -1210,7 +1213,10 @@ linux_recvmsg_common(struct thread *td, l_int s, struc
 	if (error != 0)
 		goto bad;
 
-	if (msg->msg_name) {
+	/*
+	 * Note that kern_recvit() updates msg->msg_namelen.
+	 */
+	if (msg->msg_name != NULL && msg->msg_namelen > 0) {
 		msg->msg_name = PTRIN(linux_msghdr.msg_name);
 		error = bsd_to_linux_sockaddr(sa, &lsa, msg->msg_namelen);
 		if (error == 0)

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