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From: "Tim J. Robbins" <tim@robbins.dropbear.id.au>
Subject: Re: kern/29741: ptrace(pid);ptrace(ppid) makes pid and ppid unkillable
Reply-To: "Tim J. Robbins" <tim@robbins.dropbear.id.au>
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The following reply was made to PR kern/29741; it has been noted by GNATS.

From: "Tim J. Robbins" <tim@robbins.dropbear.id.au>
To: freebsd-gnats-submit@FreeBSD.ORG
Cc: Dave Zarzycki <zarzycki@FreeBSD.ORG>
Subject: Re: kern/29741: ptrace(pid);ptrace(ppid) makes pid and ppid unkillable
Date: Sun, 27 Jan 2002 03:28:31 +1100

 I can reproduce this problem with 4.5-RC. The problem seems to be that
 ptrace() allows a process to attach to its owner. I've attached a patch
 for both RELENG_4 and -CURRENT that seems to correct the problem. When
 I try to reproduce it now:
 
 tim@descent$ gdb -q
 (gdb) file gdb
 Reading symbols from gdb...(no debugging symbols found)...done.
 (gdb) run -q
 Starting program: /usr/bin/gdb -q
 warning: shared library handler failed to enable breakpoint
 
 Program received signal SIGTRAP, Trace/breakpoint trap.
 0x2815e39c in ?? ()
 (gdb) cont
 Continuing.
 (gdb) file gdb
 Reading symbols from gdb...(no debugging symbols found)...done.
 (gdb) attach 177
 Attaching to program: /usr/bin/gdb, process 177
 ptrace: Invalid argument.
 
 I'm not exactly sure what the warning is about; it was there before I
 mucked with ptrace.
 
 Patch for RELENG_4:
 
 Index: src/sys/kern/sys_process.c
 ===================================================================
 RCS file: /home/ncvs/src/sys/kern/sys_process.c,v
 retrieving revision 1.51.2.3
 diff -c -r1.51.2.3 sys_process.c
 *** src/sys/kern/sys_process.c	2002/01/22 17:22:59	1.51.2.3
 --- src/sys/kern/sys_process.c	2002/01/26 16:19:02
 ***************
 *** 233,240 ****
   		break;
   
   	case PT_ATTACH:
 ! 		/* Self */
 ! 		if (p->p_pid == curp->p_pid)
   			return EINVAL;
   
   		/* Already traced */
 --- 233,240 ----
   		break;
   
   	case PT_ATTACH:
 ! 		/* Self or owner */
 ! 		if (p->p_pid == curp->p_pid || p->p_pid == curp->p_oppid)
   			return EINVAL;
   
   		/* Already traced */
 
 
 Patch for -CURRENT (not tested!):
 
 Index: src/sys/kern/sys_process.c
 ===================================================================
 RCS file: /home/ncvs/src/sys/kern/sys_process.c,v
 retrieving revision 1.76
 diff -c -r1.76 sys_process.c
 *** src/sys/kern/sys_process.c	2001/10/21 23:57:15	1.76
 --- src/sys/kern/sys_process.c	2002/01/26 16:20:34
 ***************
 *** 308,315 ****
   		break;
   
   	case PT_ATTACH:
 ! 		/* Self */
 ! 		if (p->p_pid == curp->p_pid) {
   			PROC_UNLOCK(p);
   			return (EINVAL);
   		}
 --- 308,315 ----
   		break;
   
   	case PT_ATTACH:
 ! 		/* Self or owner */
 ! 		if (p->p_pid == curp->p_pid || p->p_pid == curp->p_oppid) {
   			PROC_UNLOCK(p);
   			return (EINVAL);
   		}
 
 
 
 Tim

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