From owner-freebsd-bugs  Wed Feb  6  7:20: 9 2002
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Date: Wed, 6 Feb 2002 07:20:03 -0800 (PST)
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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: Dave Zarzycki <zarzycki@FreeBSD.org>
Cc: freebsd-gnats-submit@FreeBSD.org
Subject: Re: kern/29741: ptrace(pid);ptrace(ppid) makes pid and ppid unkillable
Date: Thu, 7 Feb 2002 02:10:26 +1100

 This patch (against RELENG_4) does solve the gdb -> gdb -> gdb -> grandparent
 problem.
 
 I don't think the "if (curp->p_flag & P_TRACED)" bit is even necessary at all;
 ptrace()'ing an ancestor seems like a bad idea to me, regardless of whether
 you're being traced or not.
 
 --- sys_process.c.old	Thu Feb  7 00:05:09 2002
 +++ sys_process.c	Thu Feb  7 01:27:36 2002
 @@ -203,7 +203,7 @@
  	struct proc *curp;
  	struct ptrace_args *uap;
  {
 -	struct proc *p;
 +	struct proc *p, *pp;
  	struct iovec iov;
  	struct uio uio;
  	int error = 0;
 @@ -240,6 +240,12 @@
  		/* Already traced */
  		if (p->p_flag & P_TRACED)
  			return EBUSY;
 +
 +		/* Can't trace an ancestor if you're being traced */
 +		if (curp->p_flag & P_TRACED)
 +			for (pp = curp->p_pptr; pp != NULL; pp = pp->p_pptr)
 +				if (pp == p)
 +					return EINVAL;
  
  		/* not owned by you, has done setuid (unless you're root) */
  		if ((p->p_cred->p_ruid != curp->p_cred->p_ruid) ||
 
 
 Tim

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