MFC r315647:

Handle kd == NULL gracefully with kvm_close(3)

Don't segfault in kvm_close(3) if provided a NULL pointer. Instead, return
-1 and set errno to EINVAL.

Document this new behavior explicitly.

2 files changed, 25 insertions, 2 deletions

diff --git a/lib/libkvm/kvm.c b/lib/libkvm/kvm.c
index d5a33aa..b814e8c 100644
--- a/lib/libkvm/kvm.c
+++ b/lib/libkvm/kvm.c
@@ -262,6 +262,10 @@ kvm_close(kvm_t *kd)
 {
 	int error = 0;
 
+	if (kd == NULL) {
+		errno = EINVAL;
+		return (-1);
+	}
 	if (kd->pmfd >= 0)
 		error |= close(kd->pmfd);
 	if (kd->vmfd >= 0)
diff --git a/lib/libkvm/kvm_open.3 b/lib/libkvm/kvm_open.3
index 1b62482..62b9df2 100644
--- a/lib/libkvm/kvm_open.3
+++ b/lib/libkvm/kvm_open.3
@@ -32,7 +32,7 @@
 .\"     @(#)kvm_open.3	8.3 (Berkeley) 4/19/94
 .\" $FreeBSD$
 .\"
-.Dd January 29, 2004
+.Dd March 20, 2017
 .Dt KVM_OPEN 3
 .Os
 .Sh NAME
@@ -181,10 +181,29 @@ is returned, in which case
 writes the error message into
 .Fa errbuf .
 .Pp
+.Rv -std kvm_close
+.Sh ERRORS
 The
 .Fn kvm_close
-function returns 0 on success and -1 on failure.
+function may fail and set the global variable
+.Va errno
+for any of the errors specified for
+.Xr close 2 .
+.Pp
+The
+.Fn kvm_close
+function may also fail and set
+.Va errno
+if:
+.Bl -tag -width Er
+.It Bq Er EINVAL
+The value passed via
+.Fa kd
+was
+.Dv NULL .
+.El
 .Sh SEE ALSO
+.Xr close 2 ,
 .Xr open 2 ,
 .Xr kvm 3 ,
 .Xr kvm_getargv 3 ,