d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Cause pfind() not to return processes in the PRS_NEW state. As a result,

Browse Source 
threads consuming the result of pfind() will not need to check for a NULL
credential pointer or other signs of an incompletely created process.
However, this also means that pfind() cannot be used to test for the
existence or find such a process.  Annotate pfind() to indicate that this
is the case.  A review of curent consumers seems to indicate that this is
not a problem for any of them.  This closes a number of race conditions
that could result in NULL pointer dereferences and related failure modes.
Other related races continue to exist, especially during iteration of the
allproc list without due caution.

Discussed with:	tjr, green
This commit is contained in:
Robert Watson 2004-08-14 17:15:16 +00:00
parent f13a7951e1
commit 6cbea71c82
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=133722
1 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
sys/kern/kern_proc.c
View File

@ -242,7 +242,10 @@ inferior(p)
}
/*
* Locate a process by number
* Locate a process by number; return only "live" processes -- i.e., neither
* zombies nor newly born but incompletely initialized processes. By not
* returning processes in the PRS_NEW state, we allow callers to avoid
* testing for that condition to avoid dereferencing p_ucred, et al.
*/
struct proc *
pfind(pid)
@ -253,6 +256,10 @@ pfind(pid)
sx_slock(&allproc_lock);
LIST_FOREACH(p, PIDHASH(pid), p_hash)
if (p->p_pid == pid) {
if (p->p_state == PRS_NEW) {
p = NULL;
break;
}
PROC_LOCK(p);
break;
}