From owner-freebsd-stable@FreeBSD.ORG Mon Feb 18 04:36:46 2008 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6C8BB16A421; Mon, 18 Feb 2008 04:36:46 +0000 (UTC) (envelope-from freebsd@electron-tube.net) Received: from mout.perfora.net (mout.perfora.net [74.208.4.194]) by mx1.freebsd.org (Postfix) with ESMTP id 3367613C468; Mon, 18 Feb 2008 04:36:46 +0000 (UTC) (envelope-from freebsd@electron-tube.net) Received: from [10.0.0.100] (c-66-41-19-246.hsd1.mn.comcast.net [66.41.19.246]) by mrelay.perfora.net (node=mrus1) with ESMTP (Nemesis) id 0MKpCa-1JQxY10LmJ-0007KF; Sun, 17 Feb 2008 23:24:13 -0500 Message-ID: <47B90868.7000900@electron-tube.net> Date: Sun, 17 Feb 2008 22:24:08 -0600 From: Jim Bryant User-Agent: Thunderbird 1.5 (X11/20061230) MIME-Version: 1.0 To: freebsd-fs@freebsd.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V01U2FsdGVkX18m4aZlpkrjVLAus8S+nj9gMeQSg5ef1kVfeL5 kBvaXrPkqcAljL7hUedzmZ1BOHwODKY8ldhtqzyKn8pRB4DeKh 4bKiIPYGZxwcwiK7ZMCUAgx2hLv+EHY Cc: freebsd-security@freebsd.org, FreeBSD-bugs@freebsd.org, freebsd-stable@freebsd.org Subject: How to take down a system to the point of requiring a newfs with one line of C (userland) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 18 Feb 2008 04:36:46 -0000 One line summary: Too many files in a top-level UFS-2 filesystem directory will cause a panic on mount. Kern/Critical/High Priority/SW-Bug Which FreeBSD Release You Are Using: 6.3-STABLE Environment (output of "uname -a" on the problem machine): FreeBSD wahoo.sd67dfl.org 6.3-STABLE FreeBSD 6.3-STABLE #0: Sun Feb 10 21:13:39 CST 2008 jbryant@wahoo.sd67dfl.org:/usr/obj/usr/src/sys/WAHOO-SMP i386 Note: I just cvsupped earlier, and no changes have been put into cvsup that would fix this problem. Full Description: I was doing a reorganization of my filesystems, and since I do offline installs, I keep a local distfiles collection (or did until yesterday when this happened), and in the process, put all of the distfiles on their own filesystem to be mounted under /usr/ports/distfiles. All was fine until I rebooted. On rebooting, I got a page fault panic on mount of the new distfiles filesystem. i booted again, got it again, booted again this time into single-user, and did a fsck on the filesystem, and it only showed as being "dirty", but otherwise had no problems in the eyes of fsck. booted again, instant panic. i booted an older 6.2 CD and mounted the filesystem fine. i then put that filesystem the way it was by mkdir'ing a distfiles dir and mv'ing everything into it, but on reboot it still paniced on mount. only a newfs was able to enable the filesystem to be mounted. today i did further research, thinking it had to do with the number of files in the top-level filesystem directory, and found that to be true. the short c program in the next section (how to repeat the problem) contains this. a second test shows that, after a newfs, if this done in any subdirectory of that filesystem, the panic is averted, and all is well. apparently this bug only effects top-level directories of a UFS2 filesystem. I have not attempted this to a non-UFS2 filesystem. IMHO, a security advisory should be released, since any user with write access to ANY top level directory of ANY mounted filesystem (most systems have /tmp as a world writable top level filesystem directory) can create a panic situation requiring a newfs of the said filesystem. A malicious user with root access can do this to /. Either way, on boot, or any attempt to mount said filesystem on a running system, will cause a panic, which of course will cause an unbootable system on reboot. How to repeat the problem: Compile and run the following as instructed: #include #include int main(int argc, char **argv) { int i; char buf[1024]; bzero(buf, 1024); for(i = 0; i < 10000; i++) { sprintf(buf, "touch %s%05d\n", argv[1], i); system((const char *)buf);} return(0);} /* pass a top-level mountpoint directory name of a mounted filesystem, with a trailing slash to the above as argv[1], and run. This will create 10,000 zero-length files in the specified directory. umount that filesystem. perform a shitload of sync's to make sure everything outstanding is flushed to disk on all filesystems. mount the target filesystem (preferably from a vty or serial console to catch the messages when it panics, which it will as soon as the mount is attempted). */ Fix to the problem if known: newfs(8)