From: Emil Tsalapatis <emil@etsalapatis.com>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, andrii@kernel.org, eddyz87@gmail.com,
memxor@gmail.com, daniel@iogearbox.net, netdev@vger.kernel.org,
Emil Tsalapatis <emil@etsalapatis.com>
Subject: [PATCH bpf 11/11] selftests/bpf: Test dynptr slice invalidation on skb clobber
Date: Wed, 16 Sep 2026 05:08:29 +0000 [thread overview]
Message-ID: <20260916050830.8774-12-emil@etsalapatis.com> (raw)
In-Reply-To: <20260916050830.8774-1-emil@etsalapatis.com>
Add tests that ensure that dynptr slices backed by skb memory
are invalidated on any operation that potentially moves/frees
the backing skb memory. Also test that only skb-backed dynptrs
may invalidate pointers into skbs.
Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
---
.../testing/selftests/bpf/progs/dynptr_fail.c | 183 ++++++++++++++++++
1 file changed, 183 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index 1cd61d72c..0f030f397 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -13,6 +13,9 @@
char _license[] SEC("license") = "GPL";
+extern int bpf_dynptr_memset(const struct bpf_dynptr *p, __u64 offset, __u64 size,
+ __u8 val) __ksym __weak;
+
struct test_info {
int x;
struct bpf_dynptr ptr;
@@ -1274,6 +1277,186 @@ int skb_invalid_data_slice4(struct __sk_buff *skb)
return SK_PASS;
}
+/*
+ * A kfunc that may clobber packet pointers must invalidate skb data slices.
+ */
+SEC("?tc")
+__failure __msg("invalid mem access")
+int skb_invalid_data_slice_after_dynptr_memset(struct __sk_buff *skb)
+{
+ struct bpf_dynptr ptr;
+ struct ethhdr *hdr;
+ char buffer[sizeof(*hdr)] = {};
+
+ bpf_dynptr_from_skb(skb, 0, &ptr);
+
+ hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer));
+ if (!hdr)
+ return SK_DROP;
+
+ bpf_dynptr_memset(&ptr, 0, 0, 0);
+
+ /* this should fail */
+ val = hdr->h_proto;
+
+ return SK_PASS;
+}
+
+/*
+ * A dynptr kfunc that may clobber packet pointers must not invalidate packet
+ * pointers when called with a non-skb dynptr.
+ */
+SEC("?tc")
+__success
+int pkt_ptr_valid_after_dynptr_memset_on_mem(struct __sk_buff *skb)
+{
+ struct bpf_dynptr ptr;
+ int *p = (void *)(long)skb->data;
+
+ if ((void *)(p + 1) > (void *)(long)skb->data_end)
+ return SK_DROP;
+
+ if (bpf_dynptr_from_mem(&val, sizeof(val), 0, &ptr))
+ return SK_DROP;
+
+ bpf_dynptr_memset(&ptr, 0, 0, 0);
+
+ return *p ? SK_PASS : SK_DROP;
+}
+
+__noinline
+int skb_dynptr_memset(struct __sk_buff *skb)
+{
+ struct bpf_dynptr ptr;
+
+ if (bpf_dynptr_from_skb(skb, 0, &ptr))
+ return 0;
+
+ return bpf_dynptr_memset(&ptr, 0, 0, 0);
+}
+
+/*
+ * A global subprog that may clobber packet pointers must invalidate packet
+ * pointers held by its caller.
+ */
+SEC("?tc")
+__failure __msg("invalid mem access")
+int skb_invalid_pkt_ptr_after_dynptr_memset_global(struct __sk_buff *skb)
+{
+ int *p = (void *)(long)skb->data;
+
+ if ((void *)(p + 1) > (void *)(long)skb->data_end)
+ return SK_DROP;
+
+ skb_dynptr_memset(skb);
+
+ /* this should fail */
+ val = *p;
+
+ return SK_PASS;
+}
+
+__noinline
+int skb_dynptr_memset_global_arg(struct __sk_buff *skb,
+ struct bpf_dynptr *ptr)
+{
+ int *p = (void *)(long)skb->data;
+
+ if ((void *)(p + 1) > (void *)(long)skb->data_end)
+ return SK_DROP;
+
+ bpf_dynptr_memset(ptr, 0, sizeof(*p), 0);
+
+ /* this should fail */
+ val = *p;
+
+ return SK_PASS;
+}
+
+/*
+ * A global subprog must conservatively treat a dynptr argument as possibly
+ * skb-backed when checking whether a kfunc invalidates packet pointers.
+ */
+SEC("?tc")
+__failure __msg("invalid mem access")
+int skb_invalid_pkt_ptr_after_dynptr_memset_global_arg(struct __sk_buff *skb)
+{
+ struct bpf_dynptr ptr;
+
+ if (bpf_dynptr_from_skb(skb, 0, &ptr))
+ return SK_DROP;
+
+ return skb_dynptr_memset_global_arg(skb, &ptr);
+}
+
+__noinline
+int skb_dynptr_write_global_arg(struct bpf_dynptr *ptr)
+{
+ int write_data = 0;
+
+ return bpf_dynptr_write(ptr, 0, &write_data, sizeof(write_data), 0);
+}
+
+/*
+ * A global subprog that calls bpf_dynptr_write() on a dynptr argument must
+ * invalidate packet pointers held by its caller.
+ */
+SEC("?tc")
+__failure __msg("invalid mem access")
+int skb_invalid_pkt_ptr_after_dynptr_write_global_arg(struct __sk_buff *skb)
+{
+ struct bpf_dynptr ptr;
+ int *p = (void *)(long)skb->data;
+
+ if ((void *)(p + 1) > (void *)(long)skb->data_end)
+ return SK_DROP;
+
+ if (bpf_dynptr_from_skb(skb, 0, &ptr))
+ return SK_DROP;
+
+ skb_dynptr_write_global_arg(&ptr);
+
+ /* this should fail */
+ val = *p;
+
+ return SK_PASS;
+}
+
+__noinline
+int skb_dynptr_write_global_arg_with_pkt_ptr(struct __sk_buff *skb,
+ struct bpf_dynptr *ptr)
+{
+ int write_data = 0;
+ int *p = (void *)(long)skb->data;
+
+ if ((void *)(p + 1) > (void *)(long)skb->data_end)
+ return SK_DROP;
+
+ bpf_dynptr_write(ptr, 0, &write_data, sizeof(write_data), 0);
+
+ /* this should fail */
+ val = *p;
+
+ return SK_PASS;
+}
+
+/*
+ * A global subprog must conservatively treat a dynptr argument as possibly
+ * skb-backed when checking whether bpf_dynptr_write() invalidates packet
+ * pointers in the callee.
+ */
+SEC("?tc")
+__failure __msg("invalid mem access")
+int skb_invalid_pkt_ptr_after_dynptr_write_global_arg_in_subprog(struct __sk_buff *skb)
+{
+ struct bpf_dynptr ptr;
+
+ if (bpf_dynptr_from_skb(skb, 0, &ptr))
+ return SK_DROP;
+
+ return skb_dynptr_write_global_arg_with_pkt_ptr(skb, &ptr);
+}
+
/* Read-only skb data slice is invalidated on write to skb metadata */
SEC("?tc")
__failure __msg("invalid mem access 'scalar'")
--
2.54.0
prev parent reply other threads:[~2026-09-16 5:08 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-16 5:08 [PATCH bpf 00/11] skb/arena bugfixes Emil Tsalapatis
2026-09-16 5:08 ` [PATCH bpf 01/11] bpf: Fix bounds check for skb-backed dynptrs Emil Tsalapatis
2026-09-16 11:52 ` Jiayuan Chen
2026-09-16 23:08 ` Jakub Kicinski
2026-09-16 5:08 ` [PATCH bpf 02/11] selftests/bpf: Test dynptr slices past end of skb Emil Tsalapatis
2026-09-16 5:18 ` sashiko-bot
2026-09-16 5:08 ` [PATCH bpf 03/11] bpf: Fix bpf_sock context code generation Emil Tsalapatis
2026-09-16 12:21 ` Jiayuan Chen
2026-09-16 5:08 ` [PATCH bpf 04/11] selftests/bpf: Add selftests for rx_queue_mapping context access Emil Tsalapatis
2026-09-16 5:08 ` [PATCH bpf 05/11] bpf: Reject pkt arguments in mutating subprogs Emil Tsalapatis
2026-09-16 5:57 ` Amery Hung
2026-09-16 5:58 ` Amery Hung
2026-09-16 18:41 ` Emil Tsalapatis
2026-09-16 19:26 ` Amery Hung
2026-09-16 5:08 ` [PATCH bpf 06/11] selftests/bpf: Test rejection of pkt args to " Emil Tsalapatis
2026-09-16 5:08 ` [PATCH bpf 07/11] bpf: Prevent variable arena/non-arena register contents Emil Tsalapatis
2026-09-16 5:08 ` [PATCH bpf 08/11] selftests/bpf: Test for mixed arena/nonarena code paths Emil Tsalapatis
2026-09-16 5:17 ` sashiko-bot
2026-09-16 5:08 ` [PATCH bpf 09/11] bpf: Track whether dynptr type is known Emil Tsalapatis
2026-09-16 5:22 ` sashiko-bot
2026-09-16 18:41 ` Emil Tsalapatis
2026-09-16 5:08 ` [PATCH bpf 10/11] bpf: Track skb memory invalidation by packet-backed dynptrs Emil Tsalapatis
2026-09-16 5:08 ` Emil Tsalapatis [this message]
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