Jilles Tjoelker <jil...@stack.nl> wrote in <20130802152204.ga1...@stack.nl>:
ji> You can simplify the code using the fairly new pget(). This will also ji> fix the incorrect errno when the process does not exist (should be ji> [ESRCH]). ji> ji> This change is a step in the right direction but is incomplete. Although ji> the check protects currently running processes, I do not see how it ji> prevents tracing a process that gets the same PID again after the ji> original target process has exited. This not only leaks sensitive ji> information but may also prevent tracing by the legitimate owner of the ji> process (because only one filemon will write events for a process). This ji> could be fixed by setting filemon->pid = -1 in ji> filemon_wrapper_sys_exit() and not allowing P_WEXIT and zombies in ji> FILEMON_SET_PID (PGET_NOTWEXIT disallows both). An [EBUSY] when there is ji> already a filemon monitoring the process may also be useful (or writing ji> copies of the events to all attached filemons). Thank you for your comments. Can you review the attached patch? If there is no problem, I will commit this and MFC to stable branches. -- Hiroki
Index: sys/dev/filemon/filemon.c
===================================================================
--- sys/dev/filemon/filemon.c (revision 253911)
+++ sys/dev/filemon/filemon.c (working copy)
@@ -164,13 +164,12 @@
/* Set the monitored process ID. */
case FILEMON_SET_PID:
- p = pfind(*((pid_t *)data));
- if (p == NULL)
- return (EINVAL);
- error = p_candebug(curthread, p);
- if (error == 0)
+ error = pget(*((pid_t *)data), PGET_CANDEBUG | PGET_NOTWEXIT,
+ &p);
+ if (error == 0) {
filemon->pid = p->p_pid;
- PROC_UNLOCK(p);
+ PROC_UNLOCK(p);
+ }
break;
default:
Index: sys/dev/filemon/filemon_wrapper.c
===================================================================
--- sys/dev/filemon/filemon_wrapper.c (revision 253911)
+++ sys/dev/filemon/filemon_wrapper.c (working copy)
@@ -574,6 +574,7 @@
(uintmax_t)now.tv_sec, (uintmax_t)now.tv_usec);
filemon_output(filemon, filemon->msgbufr, len);
+ filemon->pid = -1;
}
/* Unlock the found filemon structure. */
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