Date: Wed, 03 Oct 2012 19:57:54 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: freebsd-hackers <freebsd-hackers@FreeBSD.org> Subject: kvm_getprocs: gracefully handle errors in kvm_deadprocs Message-ID: <506C6E92.10803@FreeBSD.org>
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kvm_deadprocs returns -1 to signify an error.
Current kvm_getprocs code would pass this return code as 'cnt' out parameter and
would not reset return value to NULL.
This confuses some callers, most prominently procstat_getprocs, into believing
that kvm_getprocs was successful. Moreover, the code tried to use cnt=-1 as an
unsigned number to allocate some additional memory. As a result fstat -M could
try to allocate huge amount of memory e.g. when used with a kernel that didn't
match userland.
With the proposed change the error code should be handled properly.
Additionally it should now be possible to enable realloc code, which previously
contained a bug and was called even after kvm_deadprocs error.
commit 6ddf602409119eded40321e5bb349b464f24e81a
Author: Andriy Gapon <avg@icyb.net.ua>
Date: Sun Sep 23 22:52:28 2012 +0300
kvm_proc: gracefully handle errors in kvm_deadprocs, don't confuse callers
Plus fix a bug under 'notdef' (sic) section.
diff --git a/lib/libkvm/kvm_proc.c b/lib/libkvm/kvm_proc.c
index d1daf77..31258d7 100644
--- a/lib/libkvm/kvm_proc.c
+++ b/lib/libkvm/kvm_proc.c
@@ -593,9 +593,15 @@ liveout:
nprocs = kvm_deadprocs(kd, op, arg, nl[1].n_value,
nl[2].n_value, nprocs);
+ if (nprocs <= 0) {
+ _kvm_freeprocs(kd);
+ nprocs = 0;
+ }
#ifdef notdef
- size = nprocs * sizeof(struct kinfo_proc);
- (void)realloc(kd->procbase, size);
+ else {
+ size = nprocs * sizeof(struct kinfo_proc);
+ kd->procbase = realloc(kd->procbase, size);
+ }
#endif
}
*cnt = nprocs;
P.S. it might may sense to change 'count' parameter of procstat_getprocs to signed
int so that it matches kvm_getprocs interface. Alternatively, an intermediate
variable could be used to insulate signedness difference:
index 56562e1..11a817e 100644
--- a/lib/libprocstat/libprocstat.c
+++ b/lib/libprocstat/libprocstat.c
@@ -184,15 +184,18 @@ procstat_getprocs(struct procstat *procstat, int what, int arg,
struct kinfo_proc *p0, *p;
size_t len;
int name[4];
+ int cnt;
int error;
assert(procstat);
assert(count);
p = NULL;
if (procstat->type == PROCSTAT_KVM) {
- p0 = kvm_getprocs(procstat->kd, what, arg, count);
- if (p0 == NULL || count == 0)
+ *count = 0;
+ p0 = kvm_getprocs(procstat->kd, what, arg, &cnt);
+ if (p0 == NULL || cnt <= 0)
return (NULL);
+ *count = cnt;
len = *count * sizeof(*p);
p = malloc(len);
if (p == NULL) {
--
Andriy Gapon
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