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Date:      Sat, 14 Mar 2020 14:04:55 +0000 (UTC)
From:      "Bjoern A. Zeeb" <bz@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r358992 - head/sys/kern
Message-ID:  <202003141404.02EE4tXg089110@repo.freebsd.org>
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Author: bz
Date: Sat Mar 14 14:04:55 2020
New Revision: 358992
URL: https://svnweb.freebsd.org/changeset/base/358992

Log:
  kern_jail: missing \0 termination check on osrelease parameter
  
  If a user spplies a non-\0 terminated osrelease parameter reading it back
  may disclose kernel memory.
  This is a problem in case of nested jails (children.max > 0, which is not
  the default).  Otherwise root outside the jail has access to kernel memory
  by other means and root inside a jail cannot create a child jail.
  
  Add the proper \0 check at the end of a supplied osrelease parameter and
  make sure any copies of the field will be \0-terminated.
  
  Submitted by:	Hans Christian Woithe (chwoithe yahoo.com)
  MFC after:	3 days

Modified:
  head/sys/kern/kern_jail.c

Modified: head/sys/kern/kern_jail.c
==============================================================================
--- head/sys/kern/kern_jail.c	Sat Mar 14 11:55:27 2020	(r358991)
+++ head/sys/kern/kern_jail.c	Sat Mar 14 14:04:55 2020	(r358992)
@@ -865,8 +865,12 @@ kern_jail_set(struct thread *td, struct uio *optuio, i
 			    "osrelease cannot be changed after creation");
 			goto done_errmsg;
 		}
-		if (len == 0 || len >= OSRELEASELEN) {
+		if (len == 0 || osrelstr[len - 1] != '\0') {
 			error = EINVAL;
+			goto done_free;
+		}
+		if (len >= OSRELEASELEN) {
+			error = ENAMETOOLONG;
 			vfs_opterror(opts,
 			    "osrelease string must be 1-%d bytes long",
 			    OSRELEASELEN - 1);
@@ -1241,9 +1245,11 @@ kern_jail_set(struct thread *td, struct uio *optuio, i
 
 		pr->pr_osreldate = osreldt ? osreldt : ppr->pr_osreldate;
 		if (osrelstr == NULL)
-		    strcpy(pr->pr_osrelease, ppr->pr_osrelease);
+			strlcpy(pr->pr_osrelease, ppr->pr_osrelease,
+			    sizeof(pr->pr_osrelease));
 		else
-		    strcpy(pr->pr_osrelease, osrelstr);
+			strlcpy(pr->pr_osrelease, osrelstr,
+			    sizeof(pr->pr_osrelease));
 
 		LIST_INIT(&pr->pr_children);
 		mtx_init(&pr->pr_mtx, "jail mutex", NULL, MTX_DEF | MTX_DUPOK);

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