Date: Mon, 23 Jun 2008 15:41:06 GMT From: Taylor R Campbell <campbell@mumble.net> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/124908: kernel performs inadequate check for incorrect lengths when sending file descriptors over sockets Message-ID: <200806231541.m5NFf60j016284@www.freebsd.org> Resent-Message-ID: <200806231550.m5NFo1bK015158@freefall.freebsd.org>
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>Number: 124908 >Category: kern >Synopsis: kernel performs inadequate check for incorrect lengths when sending file descriptors over sockets >Confidential: no >Severity: serious >Priority: medium >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Mon Jun 23 15:50:00 UTC 2008 >Closed-Date: >Last-Modified: >Originator: Taylor R Campbell >Release: >Organization: >Environment: I have no FreeBSD machine of my own, but someone kindly offered to run a test program on a machine with the following uname -a output: FreeBSD dns.deafhogs.org 7.0-RELEASE-p2 FreeBSD 7.0-RELEASE-p2 #1: Thu Jun 19 06:47:36 EDT 2008 chaulmark@nfs.deafhogs.org:/usr/obj/usr/src/sys/GENERIC i386 >Description: In src/kern/sys/uipc_usrreq.c (rev 1.214), the function unp_internalize does not adequately check that the lengths in control message headers are correct, and as a consequence may calculate a negative number of file descriptors in the user-supplied buffer, leading potentially to disaster later on. (Thanks to Michael van Elst and Martin Husemann for alerting me to this issue in NetBSD.) >How-To-Repeat: Download the program <http://mumble.net/~campbell/tmp/fbsd-fail.c>; Compile it with gcc -DFAIL -g -Wall fbsd-fail.c -o fbsd-fail Run it with ./fbsd-fail foobar sendmsg(2) should return EINVAL, but it doesn't; instead it has random effects, such as returning EBADF, which suggests that the kernel might be examining and passing to other processes file descriptors that the user did not request. >Fix: Add the following test to the list of conditions in unp_internalize for which it will return EINVAL: cm->cmsg_len < CMSG_ALIGN(sizeof(struct cmsghdr)) >Release-Note: >Audit-Trail: >Unformatted:
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