[DTrace-devel] [PATCH v2 17/20] Allocate extra space in the strtab to help the BPF verifier
Kris Van Hees
kris.van.hees at oracle.com
Thu Jun 3 08:19:02 PDT 2021
Although the internal consistency of the strtab data (generated by
the compiler) guarantees that access to string constants will never
read outside the strtab, the BPF verifier cannot verify that through
static code analysis. By padding the strtab with enough space to
store the largest supported string we guarantee that any access up
to the maximum string size can succeed.
Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
libdtrace/dt_bpf.c | 18 ++++++++++++------
.../unittest/actions/freopen/tst.badfreopen.sh | 3 +--
test/unittest/operators/tst.ternary.d | 3 +--
test/unittest/printf/tst.basics.d | 3 +--
test/unittest/printf/tst.precs.d | 3 +--
test/unittest/printf/tst.wp.d | 3 +--
test/unittest/regression/tst.sigaltstack.d | 3 +--
test/unittest/scripting/tst.arg0.d | 6 ++----
test/unittest/scripting/tst.stringmacro.sh | 6 ++----
test/unittest/struct/tst.clauselocal.d | 3 +--
10 files changed, 23 insertions(+), 28 deletions(-)
diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
index 067bf0d5..7317abfc 100644
--- a/libdtrace/dt_bpf.c
+++ b/libdtrace/dt_bpf.c
@@ -171,7 +171,9 @@ set_task_offsets(dtrace_hdl_t *dtp)
* element (key 0) that contains the entire string table as a
* concatenation of all unique strings (each terminated with a
* NUL byte). The string table size is taken from the DTrace
- * consumer handle (dt_strlen).
+ * consumer handle (dt_strlen), and increased by the maximum
+ * string size to ensure that the BPF verifier can validate all
+ * access requests for dynamic references to string constants.
* - gvars: Global variables map. This is a global map with a singleton
* element (key 0) addressed by variable offset.
* - lvars: Local variables map. This is a per-CPU map with a singleton
@@ -198,7 +200,7 @@ set_task_offsets(dtrace_hdl_t *dtp)
int
dt_bpf_gmap_create(dtrace_hdl_t *dtp)
{
- int gvarsz, lvarsz, tvarc, aggsz;
+ int stabsz, gvarsz, lvarsz, tvarc, aggsz;
int ci_mapfd, st_mapfd;
uint32_t key = 0;
@@ -253,11 +255,15 @@ dt_bpf_gmap_create(dtrace_hdl_t *dtp)
return -1; /* dt_errno is set for us */
/*
- * We may need to create a final copy of the string table because it is
- * possible entries were added after the last clause was compiled.
+ * We need to create the global (consolidated) string table. We store
+ * the actual length (for in-code BPF validation purposes) but augment
+ * it by the maximum string size to determine the size of the BPF map
+ * vaule that is used to store the strtab.
*/
dtp->dt_strlen = dt_strtab_size(dtp->dt_ccstab);
- dtp->dt_strtab = dt_zalloc(dtp, dtp->dt_strlen);
+ stabsz = dtp->dt_strlen +
+ ctf_type_size(DT_STR_CTFP(dtp), DT_STR_TYPE(dtp));
+ dtp->dt_strtab = dt_zalloc(dtp, stabsz);
if (dtp->dt_strtab == NULL)
return dt_set_errno(dtp, EDT_NOMEM);
@@ -265,7 +271,7 @@ dt_bpf_gmap_create(dtrace_hdl_t *dtp)
dtp->dt_strtab);
st_mapfd = create_gmap(dtp, "strtab", BPF_MAP_TYPE_ARRAY,
- sizeof(uint32_t), dtp->dt_strlen, 1);
+ sizeof(uint32_t), stabsz, 1);
if (st_mapfd == -1)
return -1; /* dt_errno is set for us */
diff --git a/test/unittest/actions/freopen/tst.badfreopen.sh b/test/unittest/actions/freopen/tst.badfreopen.sh
index 21c890f2..39efd16e 100755
--- a/test/unittest/actions/freopen/tst.badfreopen.sh
+++ b/test/unittest/actions/freopen/tst.badfreopen.sh
@@ -1,11 +1,10 @@
#!/bin/bash
#
# Oracle Linux DTrace.
-# Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2006, 2021, 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.
#
-# @@xfail: dtv2
script()
{
$dtrace $dt_flags -wq -o $tmpfile -s /dev/stdin 2> $errfile <<EOF
diff --git a/test/unittest/operators/tst.ternary.d b/test/unittest/operators/tst.ternary.d
index bcf0e3cb..9d47fcc2 100644
--- a/test/unittest/operators/tst.ternary.d
+++ b/test/unittest/operators/tst.ternary.d
@@ -1,10 +1,9 @@
/*
* Oracle Linux DTrace.
- * Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2021, 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.
*/
-/* @@xfail: dtv2 */
/*
* ASSERTION:
diff --git a/test/unittest/printf/tst.basics.d b/test/unittest/printf/tst.basics.d
index 14fec099..aaf0b4c2 100644
--- a/test/unittest/printf/tst.basics.d
+++ b/test/unittest/printf/tst.basics.d
@@ -1,10 +1,9 @@
/*
* Oracle Linux DTrace.
- * Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2021, 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.
*/
-/* @@xfail: dtv2 */
/*
* ASSERTION:
diff --git a/test/unittest/printf/tst.precs.d b/test/unittest/printf/tst.precs.d
index bac8a90f..e5e6fbe5 100644
--- a/test/unittest/printf/tst.precs.d
+++ b/test/unittest/printf/tst.precs.d
@@ -1,10 +1,9 @@
/*
* Oracle Linux DTrace.
- * Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2021, 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.
*/
-/* @@xfail: dtv2 */
/*
* ASSERTION:
diff --git a/test/unittest/printf/tst.wp.d b/test/unittest/printf/tst.wp.d
index 019ca5a8..fd130f93 100644
--- a/test/unittest/printf/tst.wp.d
+++ b/test/unittest/printf/tst.wp.d
@@ -1,10 +1,9 @@
/*
* Oracle Linux DTrace.
- * Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2021, 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.
*/
-/* @@xfail: dtv2 */
/*
* ASSERTION:
diff --git a/test/unittest/regression/tst.sigaltstack.d b/test/unittest/regression/tst.sigaltstack.d
index 48f0a4e7..40535201 100644
--- a/test/unittest/regression/tst.sigaltstack.d
+++ b/test/unittest/regression/tst.sigaltstack.d
@@ -1,10 +1,9 @@
/*
* Oracle Linux DTrace.
- * Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2021, 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.
*/
-/* @@xfail: dtv2 */
#pragma D option destructive
#pragma D option quiet
diff --git a/test/unittest/scripting/tst.arg0.d b/test/unittest/scripting/tst.arg0.d
index 92e2756f..905fefb6 100644
--- a/test/unittest/scripting/tst.arg0.d
+++ b/test/unittest/scripting/tst.arg0.d
@@ -2,15 +2,13 @@
/*
* Oracle Linux DTrace.
- * Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2021, 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.
*/
-/* @@xfail: dtv2 */
/*
- * ASSERTION:
- * print argument 0 I mean "$0"
+ * ASSERTION: print script argument 0, i.e. "$0"
*
* SECTION: Scripting
*
diff --git a/test/unittest/scripting/tst.stringmacro.sh b/test/unittest/scripting/tst.stringmacro.sh
index 880fb242..6aa5c060 100755
--- a/test/unittest/scripting/tst.stringmacro.sh
+++ b/test/unittest/scripting/tst.stringmacro.sh
@@ -1,15 +1,13 @@
#!/bin/bash
#
# Oracle Linux DTrace.
-# Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2006, 2021, 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.
#
-# @@xfail: dtv2
############################################################################
-# ASSERTION:
-# Pass a bunch of strings as a sentence and print them
+# ASSERTION: Pass a bunch of strings as a sentence and print them
#
# SECTION: Scripting
#
diff --git a/test/unittest/struct/tst.clauselocal.d b/test/unittest/struct/tst.clauselocal.d
index bb822ed9..aa547fc0 100644
--- a/test/unittest/struct/tst.clauselocal.d
+++ b/test/unittest/struct/tst.clauselocal.d
@@ -1,10 +1,9 @@
/*
* Oracle Linux DTrace.
- * Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2021, 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.
*/
-/* @@xfail: dtv2 */
#pragma D option quiet
--
2.31.1
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