[PATCH bpf-next v3 0/2] bpf: Allow XDP_REDIRECT for XDP dev-bound programs

[PATCH bpf-next v3 0/2] bpf: Allow XDP_REDIRECT for XDP dev-bound programs

[Lorenzo Bianconi]

In the current implementation if the program is dev-bound to a specific
device, it will not be possible to perform XDP_REDIRECT into a DEVMAP or
CPUMAP even if the program is running in the driver NAPI context.
Fix the issue introducing __bpf_prog_map_compatible utility routine in
order to avoid bpf_prog_is_dev_bound() during the XDP program load.
Continue forbidding to attach a dev-bound program to XDP maps.

---
Changes in v3:
- move seltest changes in a dedicated patch
- Link to v2: https://lore.kernel.org/r/20250423-xdp-prog-bound-fix-v2-1-51742a5dfbce@kernel.org

Changes in v2:
- Introduce __bpf_prog_map_compatible() utility routine in order to skip
  bpf_prog_is_dev_bound check in bpf_check_tail_call()
- Extend xdp_metadata selftest
- Link to v1: https://lore.kernel.org/r/20250422-xdp-prog-bound-fix-v1-1-0b581fa186fe@kernel.org

---
Lorenzo Bianconi (2):
      bpf: Allow XDP dev-bound programs to perform XDP_REDIRECT into maps
      selftests/bpf: xdp_metadata: check XDP_REDIRCT support for dev-bound progs

 kernel/bpf/core.c                                  | 27 +++++++++++++---------
 .../selftests/bpf/prog_tests/xdp_metadata.c        | 22 +++++++++++++++++-
 tools/testing/selftests/bpf/progs/xdp_metadata.c   | 13 +++++++++++
 3 files changed, 50 insertions(+), 12 deletions(-)
---
base-commit: 91dbac4076537b464639953c055c460d2bdfc7ea
change-id: 20250422-xdp-prog-bound-fix-9f30f3e134aa

Best regards,
-- 
Lorenzo Bianconi <lorenzo@kernel.org>

[PATCH bpf-next v3 1/2] bpf: Allow XDP dev-bound programs to perform XDP_REDIRECT into maps

[Lorenzo Bianconi]

In the current implementation if the program is dev-bound to a specific
device, it will not be possible to perform XDP_REDIRECT into a DEVMAP
or CPUMAP even if the program is running in the driver NAPI context and
it is not attached to any map entry. This seems in contrast with the
explanation available in bpf_prog_map_compatible routine.
Fix the issue introducing __bpf_prog_map_compatible utility routine in
order to avoid bpf_prog_is_dev_bound() check running bpf_check_tail_call()
at program load time (bpf_prog_select_runtime()).
Continue forbidding to attach a dev-bound program to XDP maps
(BPF_MAP_TYPE_PROG_ARRAY, BPF_MAP_TYPE_DEVMAP and BPF_MAP_TYPE_CPUMAP).

Fixes: 3d76a4d3d4e59 ("bpf: XDP metadata RX kfuncs")
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 kernel/bpf/core.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index ba6b6118cf504041278d05417c4212d57be6fca0..a3e571688421196c3ceaed62b3b59b62a0258a8c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2358,8 +2358,8 @@ static unsigned int __bpf_prog_ret0_warn(const void *ctx,
 	return 0;
 }
 
-bool bpf_prog_map_compatible(struct bpf_map *map,
-			     const struct bpf_prog *fp)
+static bool __bpf_prog_map_compatible(struct bpf_map *map,
+				      const struct bpf_prog *fp)
 {
 	enum bpf_prog_type prog_type = resolve_prog_type(fp);
 	bool ret;
@@ -2368,14 +2368,6 @@ bool bpf_prog_map_compatible(struct bpf_map *map,
 	if (fp->kprobe_override)
 		return false;
 
-	/* XDP programs inserted into maps are not guaranteed to run on
-	 * a particular netdev (and can run outside driver context entirely
-	 * in the case of devmap and cpumap). Until device checks
-	 * are implemented, prohibit adding dev-bound programs to program maps.
-	 */
-	if (bpf_prog_is_dev_bound(aux))
-		return false;
-
 	spin_lock(&map->owner.lock);
 	if (!map->owner.type) {
 		/* There's no owner yet where we could check for
@@ -2409,6 +2401,19 @@ bool bpf_prog_map_compatible(struct bpf_map *map,
 	return ret;
 }
 
+bool bpf_prog_map_compatible(struct bpf_map *map, const struct bpf_prog *fp)
+{
+	/* XDP programs inserted into maps are not guaranteed to run on
+	 * a particular netdev (and can run outside driver context entirely
+	 * in the case of devmap and cpumap). Until device checks
+	 * are implemented, prohibit adding dev-bound programs to program maps.
+	 */
+	if (bpf_prog_is_dev_bound(fp->aux))
+		return false;
+
+	return __bpf_prog_map_compatible(map, fp);
+}
+
 static int bpf_check_tail_call(const struct bpf_prog *fp)
 {
 	struct bpf_prog_aux *aux = fp->aux;
@@ -2421,7 +2426,7 @@ static int bpf_check_tail_call(const struct bpf_prog *fp)
 		if (!map_type_contains_progs(map))
 			continue;
 
-		if (!bpf_prog_map_compatible(map, fp)) {
+		if (!__bpf_prog_map_compatible(map, fp)) {
 			ret = -EINVAL;
 			goto out;
 		}

-- 
2.49.0

[PATCH bpf-next v3 2/2] selftests/bpf: xdp_metadata: check XDP_REDIRCT support for dev-bound progs

[Lorenzo Bianconi]

Improve xdp_metadata bpf selftest in order to check it is possible for a
XDP dev-bound program to perform XDP_REDIRECT into a DEVMAP but it is still
not allowed to attach a XDP dev-bound program to a DEVMAP entry.

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 .../selftests/bpf/prog_tests/xdp_metadata.c        | 22 +++++++++++++++++++++-
 tools/testing/selftests/bpf/progs/xdp_metadata.c   | 13 +++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
index 3d47878ef6bfb55c236dc9df2c100fcc449f8de3..19f92affc2daa23fdd869554e7a0475b86350a4f 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
@@ -351,9 +351,10 @@ void test_xdp_metadata(void)
 	struct xdp_metadata2 *bpf_obj2 = NULL;
 	struct xdp_metadata *bpf_obj = NULL;
 	struct bpf_program *new_prog, *prog;
+	struct bpf_devmap_val devmap_e = {};
+	struct bpf_map *prog_arr, *devmap;
 	struct nstoken *tok = NULL;
 	__u32 queue_id = QUEUE_ID;
-	struct bpf_map *prog_arr;
 	struct xsk tx_xsk = {};
 	struct xsk rx_xsk = {};
 	__u32 val, key = 0;
@@ -409,6 +410,13 @@ void test_xdp_metadata(void)
 	bpf_program__set_ifindex(prog, rx_ifindex);
 	bpf_program__set_flags(prog, BPF_F_XDP_DEV_BOUND_ONLY);
 
+	/* Make sure we can load a dev-bound program that performs
+	 * XDP_REDIRECT into a devmap.
+	 */
+	new_prog = bpf_object__find_program_by_name(bpf_obj->obj, "redirect");
+	bpf_program__set_ifindex(new_prog, rx_ifindex);
+	bpf_program__set_flags(new_prog, BPF_F_XDP_DEV_BOUND_ONLY);
+
 	if (!ASSERT_OK(xdp_metadata__load(bpf_obj), "load skeleton"))
 		goto out;
 
@@ -423,6 +431,18 @@ void test_xdp_metadata(void)
 			"update prog_arr"))
 		goto out;
 
+	/* Make sure we can't add dev-bound programs to devmaps. */
+	devmap = bpf_object__find_map_by_name(bpf_obj->obj, "dev_map");
+	if (!ASSERT_OK_PTR(devmap, "no dev_map found"))
+		goto out;
+
+	devmap_e.bpf_prog.fd = val;
+	if (!ASSERT_ERR(bpf_map__update_elem(devmap, &key, sizeof(key),
+					     &devmap_e, sizeof(devmap_e),
+					     BPF_ANY),
+			"update dev_map"))
+		goto out;
+
 	/* Attach BPF program to RX interface. */
 
 	ret = bpf_xdp_attach(rx_ifindex,
diff --git a/tools/testing/selftests/bpf/progs/xdp_metadata.c b/tools/testing/selftests/bpf/progs/xdp_metadata.c
index 31ca229bb3c0f182483334a4ab0bd204acae20f3..09bb8a038d528cf26c5b314cc927915ac2796bf0 100644
--- a/tools/testing/selftests/bpf/progs/xdp_metadata.c
+++ b/tools/testing/selftests/bpf/progs/xdp_metadata.c
@@ -19,6 +19,13 @@ struct {
 	__type(value, __u32);
 } prog_arr SEC(".maps");
 
+struct {
+	__uint(type, BPF_MAP_TYPE_DEVMAP);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(struct bpf_devmap_val));
+	__uint(max_entries, 1);
+} dev_map SEC(".maps");
+
 extern int bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx,
 					 __u64 *timestamp) __ksym;
 extern int bpf_xdp_metadata_rx_hash(const struct xdp_md *ctx, __u32 *hash,
@@ -95,4 +102,10 @@ int rx(struct xdp_md *ctx)
 	return bpf_redirect_map(&xsk, ctx->rx_queue_index, XDP_PASS);
 }
 
+SEC("xdp")
+int redirect(struct xdp_md *ctx)
+{
+	return bpf_redirect_map(&dev_map, ctx->rx_queue_index, XDP_PASS);
+}
+
 char _license[] SEC("license") = "GPL";

-- 
2.49.0

Re: [PATCH bpf-next v3 0/2] bpf: Allow XDP_REDIRECT for XDP dev-bound programs

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Martin KaFai Lau <martin.lau@kernel.org>:

On Mon, 28 Apr 2025 17:44:01 +0200 you wrote:
> In the current implementation if the program is dev-bound to a specific
> device, it will not be possible to perform XDP_REDIRECT into a DEVMAP or
> CPUMAP even if the program is running in the driver NAPI context.
> Fix the issue introducing __bpf_prog_map_compatible utility routine in
> order to avoid bpf_prog_is_dev_bound() during the XDP program load.
> Continue forbidding to attach a dev-bound program to XDP maps.
> 
> [...]

Here is the summary with links:
  - [bpf-next,v3,1/2] bpf: Allow XDP dev-bound programs to perform XDP_REDIRECT into maps
    https://git.kernel.org/bpf/bpf-next/c/714070c4cb7a
  - [bpf-next,v3,2/2] selftests/bpf: xdp_metadata: check XDP_REDIRCT support for dev-bound progs
    https://git.kernel.org/bpf/bpf-next/c/3678331ca781

You are awesome, thank you!
-- 
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