Date: Fri, 30 Apr 2010 02:04:48 GMT From: Gunnar Hinriksson <tomtinn@gmail.com> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/146167: ptrace PT_DETACH undocumented behavior Message-ID: <201004300204.o3U24mj9044086@www.freebsd.org> Resent-Message-ID: <201004300210.o3U2A1qK039932@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 146167
>Category: kern
>Synopsis: ptrace PT_DETACH undocumented behavior
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Apr 30 02:10:01 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator: Gunnar Hinriksson
>Release: 8.0-RELEASE-p2
>Organization:
>Environment:
FreeBSD knut 8.0-RELEASE-p2 FreeBSD 8.0-RELEASE-p2 #0: Tue Apr 27 04:36:16 UTC 2010 gunnar@knut:/usr/obj/usr/src/sys/GENERIC amd64
>Description:
When using PT_DETACH on ptrace the (caddr_t addr) parameter is not ignored like the documentation suggests.
Instead it proceeds to change the execution address to the value of the parameter if it is not (void *)1.
This can cause portability problems from other systems that implement ptrace and assume that the parameter is ignored.
>How-To-Repeat:
Write a program that uses ptrace to attach to another process and then detach with the parameter (caddr_t addr) value not equal to 1.
This can cause the child process to segfault.
>Fix:
Attached patch.
Patch attached with submission follows:
--- /usr/src/sys/kern/sys_process.c 2009-10-25 01:10:29.000000000 +0000
+++ sys_process.c 2010-04-30 01:32:52.507274805 +0000
@@ -741,10 +741,13 @@
break;
}
- if (addr != (void *)1) {
- error = ptrace_set_pc(td2, (u_long)(uintfptr_t)addr);
- if (error)
- break;
+ if (req == PT_CONTINUE)
+ {
+ if (addr != (void *)1) {
+ error = ptrace_set_pc(td2, (u_long)(uintfptr_t)addr);
+ if (error)
+ break;
+ }
}
if (req == PT_DETACH) {
>Release-Note:
>Audit-Trail:
>Unformatted:
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201004300204.o3U24mj9044086>