Re: [PATCH] Add prctl to modify current->comm

[Andi Kleen <ak@suse.de>]

On Tue, Sep 07, 2004 at 06:12:48PM +0100, Alan Cox wrote:
> > +		case PR_SET_NAME: {
> > +			struct task_struct *me = current;
> > +			me->comm[sizeof(me->comm)-1] = 0;
> > +			if (strncpy_from_user(me->comm, (char *)arg2, sizeof(me->comm)-1) < 0)
> > +				return -EFAULT;
> > +			return 0;
> > +		}
> 
> If the strncpy_from_user faults the state of current->comm is undefined.

I didn't see it as a big issue because the result will be 0 terminated
anyways. 

> This strikes me as bad design.

Here's is a new patch with this fixed. 

-Andi

--------------------------------------------------------------------

Allow a program to change its current->comm

Useful for KDE & kdeinit. 


diff -u linux-2.6.8-5/kernel/sys.c-o linux-2.6.8-5/kernel/sys.c
--- linux-2.6.8-5/kernel/sys.c-o	2004-08-14 07:36:16.000000000 +0200
+++ linux-2.6.8-5/kernel/sys.c	2004-09-07 23:09:56.000000000 +0200
@@ -1660,6 +1660,15 @@
 			}
 			current->keep_capabilities = arg2;
 			break;
+		case PR_SET_NAME: {
+			struct task_struct *me = current;
+			unsigned char ncomm[sizeof(me->comm)];
+			ncomm[sizeof(me->comm)-1] = 0;
+			if (strncpy_from_user(ncomm, (char *)arg2, sizeof(me->comm)-1) < 0)
+				return -EFAULT;
+			memcpy(me->comm, ncomm, sizeof(me->comm));
+			return 0;
+		}
 		default:
 			error = -EINVAL;
 			break;
diff -u linux-2.6.8-5/include/linux/prctl.h-o linux-2.6.8-5/include/linux/prctl.h
--- linux-2.6.8-5/include/linux/prctl.h-o	2004-08-14 07:37:14.000000000 +0200
+++ linux-2.6.8-5/include/linux/prctl.h	2004-09-07 23:09:44.000000000 +0200
@@ -49,5 +49,6 @@
 # define PR_TIMING_TIMESTAMP    1       /* Accurate timestamp based
                                                    process timing */
 
+#define PR_SET_NAME    15		/* Set process name. */
 
 #endif /* _LINUX_PRCTL_H */