Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756019AbYH3TqS (ORCPT ); Sat, 30 Aug 2008 15:46:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751494AbYH3TqG (ORCPT ); Sat, 30 Aug 2008 15:46:06 -0400 Received: from fg-out-1718.google.com ([72.14.220.155]:42797 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752463AbYH3TqF (ORCPT ); Sat, 30 Aug 2008 15:46:05 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=uVBQVh8xzkF9i/h62E84kMg3J3gajTdLGjFwGZt5379YyjNVebchLH9/Kj1bqLLo1k hJrJR9f4GNRsD2qecEqh30PWTShZ4ja3jwsPEaZ6R0gQJhBX/0uW56vxQX8vwA1+ef94 V0VlAHD5e0tH1MiVaEgPf8uf2kSFvy8242LRg= Date: Sat, 30 Aug 2008 23:45:55 +0400 From: Cyrill Gorcunov To: Vegard Nossum Cc: Tom Tucker , Neil Brown , Chuck Lever , Greg Banks , "J. Bruce Fields" , linux-kernel@vger.kernel.org Subject: Re: buffer overflow in /proc/sys/sunrpc/transports Message-ID: <20080830194555.GG7611@lenovo> References: <20080830184422.GA9598@localhost.localdomain> <20080830190642.GC7611@lenovo> <19f34abd0808301242j63d357f5h7afd3eff796a4cf0@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <19f34abd0808301242j63d357f5h7afd3eff796a4cf0@mail.gmail.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3183 Lines: 82 [Vegard Nossum - Sat, Aug 30, 2008 at 09:42:30PM +0200] | On Sat, Aug 30, 2008 at 9:06 PM, Cyrill Gorcunov wrote: | > [Vegard Nossum - Sat, Aug 30, 2008 at 08:44:22PM +0200] | > | Hi, | > | | > | I noticed that something weird is going on with /proc/sys/sunrpc/transports. | > | This file is generated in net/sunrpc/sysctl.c, function proc_do_xprt(). When | > | I "cat" this file, I get the expected output: | > | | > | $ cat /proc/sys/sunrpc/transports | > | tcp 1048576 | > | udp 32768 | > | | > | But I think that it does not check the length of the buffer supplied by | > | userspace to read(). With my original program, I found that the stack was | > | being overwritten by the characters above, even when the length given to | > | read() was just 1. So I have created a test program, see it at the bottom of | > | this e-mail. Here is its output: | > | | > ... | > | > Indeed, maybe just add checking for user buffer length? | > As proc_dodebug() in this file are doing. I don't think | > the user would be happy with his stack burned :) | > | > Something like: | > --- | > | > Index: linux-2.6.git/net/sunrpc/sysctl.c | > =================================================================== | > --- linux-2.6.git.orig/net/sunrpc/sysctl.c 2008-07-20 11:40:14.000000000 +0400 | > +++ linux-2.6.git/net/sunrpc/sysctl.c 2008-08-30 23:05:30.000000000 +0400 | > @@ -69,6 +69,8 @@ static int proc_do_xprt(ctl_table *table | > return -EINVAL; | > else { | > len = svc_print_xprts(tmpbuf, sizeof(tmpbuf)); | > + if (*lenp < len) | > + return -EFAULT; | > if (!access_ok(VERIFY_WRITE, buffer, len)) | > return -EFAULT; | > | > | | BTW, look at this: | | $ od -A x -t x1z /proc/sys/sunrpc/transports | 000000 74 63 70 20 31 30 34 38 35 37 36 0a 75 64 70 20 >tcp 1048576.udp < | 000010 33 32 37 36 38 0a 00 00 00 00 00 00 00 00 00 00 >32768...........< | 000020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< | * | 0003e0 00 00 00 00 00 00 00 00 00 00 >..........< | 0003ea | | ...and: | | $ strace -e trace=read cat /proc/sys/sunrpc/transports > /dev/null | read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@G\316E4\0\0\0"..., | 512) = 512 | read(3, "tcp 1048576\nudp 32768\n\0\0\0\0\0\0\0\0\0\0"..., 4096) = 4074 | read(3, "", 4096) = 0 | | ...why does it have a huge return value? The output is only about 40 | bytes... why add all the \0? Would your patch also fix this? | | | Vegard Get me some time to check | | -- | "The animistic metaphor of the bug that maliciously sneaked in while | the programmer was not looking is intellectually dishonest as it | disguises that the error is the programmer's own creation." | -- E. W. Dijkstra, EWD1036 | - Cyrill - -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/