[DTrace-devel] [PATCH] Check pid==0 for uaddr2str

[eugene.loh at oracle.com]

From: Eugene Loh <eugene.loh at oracle.com>

If dtrace_uaddr2str() is given pid==0, it will try to look up the
pid, get a NULL pointer back, dereference it, and cause dtrace to
segfault.

Add a check for pid==0.

Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
---
 libdtrace/dt_subr.c                   |  2 +-
 test/unittest/ustack/tst.uaddr-pid0.d | 17 +++++++++++++++++
 test/unittest/ustack/tst.uaddr-pid0.r |  1 +
 test/unittest/ustack/tst.ufunc-pid0.d | 17 +++++++++++++++++
 test/unittest/ustack/tst.ufunc-pid0.r |  1 +
 test/unittest/ustack/tst.usym-pid0.d  | 17 +++++++++++++++++
 test/unittest/ustack/tst.usym-pid0.r  |  1 +
 7 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 test/unittest/ustack/tst.uaddr-pid0.d
 create mode 100644 test/unittest/ustack/tst.uaddr-pid0.r
 create mode 100644 test/unittest/ustack/tst.ufunc-pid0.d
 create mode 100644 test/unittest/ustack/tst.ufunc-pid0.r
 create mode 100644 test/unittest/ustack/tst.usym-pid0.d
 create mode 100644 test/unittest/ustack/tst.usym-pid0.r

diff --git a/libdtrace/dt_subr.c b/libdtrace/dt_subr.c
index 3a93eed7..bff0497a 100644
--- a/libdtrace/dt_subr.c
+++ b/libdtrace/dt_subr.c
@@ -888,7 +888,7 @@ dtrace_uaddr2str(dtrace_hdl_t *dtp, pid_t pid, uint64_t addr, char *str,
 		pid = dt_proc_grab_lock(dtp, pid, DTRACE_PROC_WAITING |
 					DTRACE_PROC_SHORTLIVED);
 
-	if (pid < 0) {
+	if (pid <= 0) {
 		snprintf(c, sizeof(c), "0x%llx", (unsigned long long)addr);
 		return dt_string2str(c, str, nbytes);
 	}
diff --git a/test/unittest/ustack/tst.uaddr-pid0.d b/test/unittest/ustack/tst.uaddr-pid0.d
new file mode 100644
index 00000000..263a7ca9
--- /dev/null
+++ b/test/unittest/ustack/tst.uaddr-pid0.d
@@ -0,0 +1,17 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ */
+
+/* Without a trigger, pid will be 0, but we should not segfault. */
+
+#pragma D option quiet
+
+tick-1
+/pid == $target/
+{
+    uaddr(ucaller);
+    exit(0);
+}
diff --git a/test/unittest/ustack/tst.uaddr-pid0.r b/test/unittest/ustack/tst.uaddr-pid0.r
new file mode 100644
index 00000000..a8e68f4e
--- /dev/null
+++ b/test/unittest/ustack/tst.uaddr-pid0.r
@@ -0,0 +1 @@
+  {ptr}                                               
diff --git a/test/unittest/ustack/tst.ufunc-pid0.d b/test/unittest/ustack/tst.ufunc-pid0.d
new file mode 100644
index 00000000..f076782a
--- /dev/null
+++ b/test/unittest/ustack/tst.ufunc-pid0.d
@@ -0,0 +1,17 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ */
+
+/* Without a trigger, pid will be 0, but we should not segfault. */
+
+#pragma D option quiet
+
+tick-1
+/pid == $target/
+{
+    ufunc(ucaller);
+    exit(0);
+}
diff --git a/test/unittest/ustack/tst.ufunc-pid0.r b/test/unittest/ustack/tst.ufunc-pid0.r
new file mode 100644
index 00000000..a8e68f4e
--- /dev/null
+++ b/test/unittest/ustack/tst.ufunc-pid0.r
@@ -0,0 +1 @@
+  {ptr}                                               
diff --git a/test/unittest/ustack/tst.usym-pid0.d b/test/unittest/ustack/tst.usym-pid0.d
new file mode 100644
index 00000000..d2f5ec5d
--- /dev/null
+++ b/test/unittest/ustack/tst.usym-pid0.d
@@ -0,0 +1,17 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ */
+
+/* Without a trigger, pid will be 0, but we should not segfault. */
+
+#pragma D option quiet
+
+tick-1
+/pid == $target/
+{
+    usym(ucaller);
+    exit(0);
+}
diff --git a/test/unittest/ustack/tst.usym-pid0.r b/test/unittest/ustack/tst.usym-pid0.r
new file mode 100644
index 00000000..a8e68f4e
--- /dev/null
+++ b/test/unittest/ustack/tst.usym-pid0.r
@@ -0,0 +1 @@
+  {ptr}                                               
-- 
2.18.4