selftests/bpf: Test using dynptr after freeing the underlying object

Make sure the verifier invalidates the dynptr and dynptr slice derived
from an skb after the skb is freed.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-14-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr.c
new file mode 100644 (file)
index 0000000..1d96f79
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include "bpf_experimental.h"
+#include "bpf_qdisc_common.h"
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+int proto;
+
+SEC("struct_ops")
+__failure __msg("Expected an initialized dynptr as R1")
+int BPF_PROG(invalid_dynptr, struct sk_buff *skb, struct Qdisc *sch,
+            struct bpf_sk_buff_ptr *to_free)
+{
+       struct bpf_dynptr ptr;
+       struct ethhdr *hdr;
+
+       bpf_dynptr_from_skb((struct __sk_buff *)skb, 0, &ptr);
+
+       bpf_qdisc_skb_drop(skb, to_free);
+
+       hdr = bpf_dynptr_slice(&ptr, 0, NULL, sizeof(*hdr));
+       if (!hdr)
+               return NET_XMIT_DROP;
+
+       proto = hdr->h_proto;
+
+       return NET_XMIT_DROP;
+}
+
+SEC("struct_ops")
+__auxiliary
+struct sk_buff *BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc *sch)
+{
+       return NULL;
+}
+
+SEC("struct_ops")
+__auxiliary
+int BPF_PROG(bpf_qdisc_test_init, struct Qdisc *sch, struct nlattr *opt,
+            struct netlink_ext_ack *extack)
+{
+       return 0;
+}
+
+SEC("struct_ops")
+__auxiliary
+void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc *sch)
+{
+}
+
+SEC("struct_ops")
+__auxiliary
+void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc *sch)
+{
+}
+
+SEC(".struct_ops")
+struct Qdisc_ops test = {
+       .enqueue   = (void *)invalid_dynptr,
+       .dequeue   = (void *)bpf_qdisc_test_dequeue,
+       .init      = (void *)bpf_qdisc_test_init,
+       .reset     = (void *)bpf_qdisc_test_reset,
+       .destroy   = (void *)bpf_qdisc_test_destroy,
+       .id        = "bpf_qdisc_test",
+};

diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_cross_frame.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_cross_frame.c
new file mode 100644 (file)
index 0000000..2e23b85
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_cross_frame.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include "bpf_experimental.h"
+#include "bpf_qdisc_common.h"
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+int proto;
+
+static __noinline int free_skb(struct sk_buff *skb)
+{
+       bpf_kfree_skb(skb);
+       return 0;
+}
+
+SEC("struct_ops")
+__failure __msg("invalid mem access 'scalar'")
+int BPF_PROG(invalid_dynptr_cross_frame, struct sk_buff *skb, struct Qdisc *sch,
+            struct bpf_sk_buff_ptr *to_free)
+{
+       struct bpf_dynptr ptr;
+       struct ethhdr *hdr;
+
+       bpf_dynptr_from_skb((struct __sk_buff *)skb, 0, &ptr);
+
+       hdr = bpf_dynptr_slice(&ptr, 0, NULL, sizeof(*hdr));
+       if (!hdr)
+               return NET_XMIT_DROP;
+
+       free_skb(skb);
+
+       proto = hdr->h_proto;
+
+       return NET_XMIT_DROP;
+}
+
+SEC("struct_ops")
+__auxiliary
+struct sk_buff *BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc *sch)
+{
+       return NULL;
+}
+
+SEC("struct_ops")
+__auxiliary
+int BPF_PROG(bpf_qdisc_test_init, struct Qdisc *sch, struct nlattr *opt,
+            struct netlink_ext_ack *extack)
+{
+       return 0;
+}
+
+SEC("struct_ops")
+__auxiliary
+void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc *sch)
+{
+}
+
+SEC("struct_ops")
+__auxiliary
+void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc *sch)
+{
+}
+
+SEC(".struct_ops")
+struct Qdisc_ops test = {
+       .enqueue   = (void *)invalid_dynptr_cross_frame,
+       .dequeue   = (void *)bpf_qdisc_test_dequeue,
+       .init      = (void *)bpf_qdisc_test_init,
+       .reset     = (void *)bpf_qdisc_test_reset,
+       .destroy   = (void *)bpf_qdisc_test_destroy,
+       .id        = "bpf_qdisc_test",
+};

diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_slice.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_slice.c
new file mode 100644 (file)
index 0000000..731216c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_slice.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include "bpf_experimental.h"
+#include "bpf_qdisc_common.h"
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+int proto;
+
+SEC("struct_ops")
+__failure __msg("invalid mem access 'scalar'")
+int BPF_PROG(invalid_dynptr_slice, struct sk_buff *skb, struct Qdisc *sch,
+            struct bpf_sk_buff_ptr *to_free)
+{
+       struct bpf_dynptr ptr;
+       struct ethhdr *hdr;
+
+       bpf_dynptr_from_skb((struct __sk_buff *)skb, 0, &ptr);
+
+       hdr = bpf_dynptr_slice(&ptr, 0, NULL, sizeof(*hdr));
+       if (!hdr) {
+               bpf_qdisc_skb_drop(skb, to_free);
+               return NET_XMIT_DROP;
+       }
+
+       bpf_qdisc_skb_drop(skb, to_free);
+
+       proto = hdr->h_proto;
+
+       return NET_XMIT_DROP;
+}
+
+SEC("struct_ops")
+__auxiliary
+struct sk_buff *BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc *sch)
+{
+       return NULL;
+}
+
+SEC("struct_ops")
+__auxiliary
+int BPF_PROG(bpf_qdisc_test_init, struct Qdisc *sch, struct nlattr *opt,
+            struct netlink_ext_ack *extack)
+{
+       return 0;
+}
+
+SEC("struct_ops")
+__auxiliary
+void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc *sch)
+{
+}
+
+SEC("struct_ops")
+__auxiliary
+void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc *sch)
+{
+}
+
+SEC(".struct_ops")
+struct Qdisc_ops test = {
+       .enqueue   = (void *)invalid_dynptr_slice,
+       .dequeue   = (void *)bpf_qdisc_test_dequeue,
+       .init      = (void *)bpf_qdisc_test_init,
+       .reset     = (void *)bpf_qdisc_test_reset,
+       .destroy   = (void *)bpf_qdisc_test_destroy,
+       .id        = "bpf_qdisc_test",
+};