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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Mon, 14 Nov 2016 13:20:10 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Subject: svn commit: r308642 - head/sys/kern
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Author: kib
Date: Mon Nov 14 13:20:10 2016
New Revision: 308642
URL: https://svnweb.freebsd.org/changeset/base/308642

Log:
  Initialize reserved bytes in struct mq_attr and its 32compat
  counterpart, to avoid kernel stack content leak in kmq_setattr(2)
  syscall.  Also slightly simplify the checks around copyout()s.
  
  Reported by:	Vlad Tsyrklevich <vlad902+spam@gmail.com>
  PR:	214488
  MFC after:	1 week

Modified:
  head/sys/kern/uipc_mqueue.c

Modified: head/sys/kern/uipc_mqueue.c
==============================================================================
--- head/sys/kern/uipc_mqueue.c	Mon Nov 14 12:56:18 2016	(r308641)
+++ head/sys/kern/uipc_mqueue.c	Mon Nov 14 13:20:10 2016	(r308642)
@@ -2242,10 +2242,10 @@ sys_kmq_setattr(struct thread *td, struc
 	}
 	error = kern_kmq_setattr(td, uap->mqd, uap->attr != NULL ? &attr : NULL,
 	    &oattr);
-	if (error != 0)
-		return (error);
-	if (uap->oattr != NULL)
+	if (error == 0 && uap->oattr != NULL) {
+		bzero(oattr.__reserved, sizeof(oattr.__reserved));
 		error = copyout(&oattr, uap->oattr, sizeof(oattr));
+	}
 	return (error);
 }
 
@@ -2759,10 +2759,9 @@ freebsd32_kmq_setattr(struct thread *td,
 	}
 	error = kern_kmq_setattr(td, uap->mqd, uap->attr != NULL ? &attr : NULL,
 	    &oattr);
-	if (error != 0)
-		return (error);
-	if (uap->oattr != NULL) {
+	if (error == 0 && uap->oattr != NULL) {
 		mq_attr_to32(&oattr, &oattr32);
+		bzero(oattr32.__reserved, sizeof(oattr32.__reserved));
 		error = copyout(&oattr32, uap->oattr, sizeof(oattr32));
 	}
 	return (error);