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Full Discussion: Problem about Kernel oops
Top Forums Programming Problem about Kernel oops Post 302588173 by homeboy on Saturday 7th of January 2012 08:39:39 AM
Old 01-07-2012
Problem about Kernel oops

hello,everyone,I'm reading LDD3.Topics about oops,it said the code bellow would cause a fault condition because "this method copies a string to a local variable,unfortunately,the string is longer than the destination array".Well,hard to understand....Is that right?I thought the fault should be caused by the wrong memset,it overwrite the function stack,the value of __user is 0xff now.will anyone tell me what happened here?Thanks;
Code:
size_t fauly_read(struct file *filp, char __user *buf, size_t count, loff_t *pos)
{
      int ret;
      char stack_buf[4];

      memset(stack_buf, 0xff, 20);
      if(count > 4)
           count  = 4;

      ret = copy_to_user(buf, stack_buf, count);
      if(!ret)
          return count;

      return ret;
}

 
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NETDUMP-CLIENT(8)						  System Programs						 NETDUMP-CLIENT(8)

NAME
netdump - send oops data and memory dumps over the network SYNOPSIS
/etc/init.d/netdump (start|stop|status|restart|propagate) DESCRIPTION
Loads and configures the netdump kernel modules. Once these are loaded, when the kernel crashes it will send the oops message and a dump of physical memory to the machine that runs the netdump-server. This can then be used to debug the problem using gdb and a kernel image. OPTIONS
start Starts the netdump client service. Loads the kernel modules with the right options. stop Unloads the kernel modules. status Shows the status of the netdump client restart Restarts the netclient modules with new configurations. propagate Sends the ssh public key needed to update the random key for each netdump session to the netdump server. FILES
/etc/sysconfig/netdump Configuration for the netdump client. You need to at least specify the address of the machine running the netdump server here. /etc/sysconfig/netdump_id_dsa.pub Public key for this machine. Used by the server to authenticate the client. This must be installed on the server, possibly by using the the propagate capability of the netdump init script, which does: cat /etc/sysconfig/netdump_id_dsa.pu | ssh netdump@$NETDUMPADDR cat '>>' /var/crash/.ssh/authorized_keys2 Where $NETDUMPADDR is the ip or name of the machine running the netdump server. SEE ALSO
netdump-server(8), init(8) BUGS
Report any bugs you find to http://bugzilla.redhat.com/bugzilla AUTHOR
Alexander Larsson <alexl@redhat.com> Linux 14 Feb 2002 NETDUMP-CLIENT(8)

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