[PATCH v2 bpf 0/6] bpf: tcp: Fix type confusion in bpf helper functions.

[PATCH v2 bpf 0/6] bpf: tcp: Fix type confusion in bpf helper functions.

[Kuniyuki Iwashima]

bpf_tcp_sock() only check if sk->sk_protocol is IPPROTO_TCP,
but RAW socket can bypass it:

  socket(AF_INET, SOCK_RAW, IPPROTO_TCP)

The same issues exist in other bpf functions:

  * bpf_mptcp_sock_from_subflow()
  * bpf_skc_to_tcp_sock()
  * bpf_skc_to_tcp6_sock()
  * sol_tcp_sockopt()

Patch 1 fixes bpf_tcp_sock() and Patch 2 adds a test for it.
Patch 3 ~ 6 fix the rest of the functions above.


Changes:
  v2:
    * Inverse if (err) to if (!err) in the selftest
    * Add patch 3 ~ 6

  v1: https://lore.kernel.org/bpf/20260430184405.1227386-1-kuniyu@google.com/
      https://lore.kernel.org/mptcp/20260430-mptcp-bpf-mptcp-sock-type-v1-1-d2ed5cda7da9@kernel.org/


Kuniyuki Iwashima (5):
  bpf: tcp: Fix type confusion in bpf_tcp_sock().
  selftest: bpf: Add test for bpf_tcp_sock() and RAW socket.
  bpf: tcp: Fix type confusion in bpf_skc_to_tcp_sock().
  bpf: tcp: Fix type confusion in bpf_skc_to_tcp6_sock().
  bpf: tcp: Fix type confusion in sol_tcp_sockopt().

Matthieu Baerts (NGI0) (1):
  mptcp: bpf: fix type confusion in bpf_mptcp_sock_from_subflow()

 net/core/filter.c                              |  8 ++++----
 net/mptcp/bpf.c                                |  2 +-
 .../selftests/bpf/prog_tests/sockopt_sk.c      | 18 +++++++++++++++++-
 tools/testing/selftests/bpf/progs/sockopt_sk.c | 16 ++++++++++++++++
 4 files changed, 38 insertions(+), 6 deletions(-)

-- 
2.54.0.545.g6539524ca2-goog

[PATCH v2 bpf 1/6] bpf: tcp: Fix type confusion in bpf_tcp_sock().

[Kuniyuki Iwashima]

bpf_tcp_sock() only checks if sk->sk_protocol is IPPROTO_TCP,
but RAW socket can bypass it:

  socket(AF_INET, SOCK_RAW, IPPROTO_TCP)

Calling bpf_setsockopt() in SOCKOPT prog triggers out-of-bounds
access to another slab object. [0]

Let's use sk_is_tcp().

[0]:
BUG: KASAN: slab-out-of-bounds in sol_tcp_sockopt (net/core/filter.c:5519)
Read of size 8 at addr ffff88801083d760 by task test_progs/1259

CPU: 1 UID: 0 PID: 1259 Comm: test_progs Tainted: G           OE       7.0.0-11175-gb5c111f4967b #1 PREEMPT(full)
Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
 print_report (mm/kasan/report.c:378 mm/kasan/report.c:482)
 kasan_report (mm/kasan/report.c:595)
 sol_tcp_sockopt (net/core/filter.c:5519)
 __bpf_getsockopt (net/core/filter.c:5633)
 bpf_sk_getsockopt (net/core/filter.c:5654)
 bpf_prog_629ba00a1601e9f2__setsockopt+0x86/0x22c
 __cgroup_bpf_run_filter_setsockopt (./include/linux/bpf.h:1402 ./include/linux/filter.h:722 ./include/linux/filter.h:729 kernel/bpf/cgroup.c:81 kernel/bpf/cgroup.c:2026)
 do_sock_setsockopt (net/socket.c:2363)
 __x64_sys_setsockopt (net/socket.c:2406)
 do_syscall_64 (arch/x86/entry/syscall_64.c:63)
 entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
RIP: 0033:0x7f85f82fe7de
Code: 55 48 63 c9 48 63 ff 45 89 c9 48 89 e5 48 83 ec 08 6a 2c e8 34 69 f7 ff c9 c3 66 90 f3 0f 1e fa 49 89 ca b8 36 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 0a c3 66 0f 1f 84 00 00 00 00 00 48 8b 15 e1
RSP: 002b:00007ffe59dcecd8 EFLAGS: 00000202 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f85f82fe7de
RDX: 000000000000001c RSI: 0000000000000006 RDI: 000000000000000d
RBP: 00007ffe59dcef20 R08: 000000000000003c R09: 0000000000000000
R10: 00007ffe59dcef00 R11: 0000000000000202 R12: 00007ffe59dcf268
R13: 0000000000000003 R14: 00007f85f9da5000 R15: 000055b2f3201400
 </TASK>

The buggy address belongs to the object at ffff88801083d280
 which belongs to the cache RAW of size 1792
The buggy address is located 1248 bytes inside of
 allocated 1792-byte region [ffff88801083d280, ffff88801083d980)

Fixes: 655a51e536c0 ("bpf: Add struct bpf_tcp_sock and BPF_FUNC_tcp_sock")
Reported-by: Damiano Melotti <melotti@google.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index bc96c18df4e0..cd88633f8dc1 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7475,7 +7475,7 @@ u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
 
 BPF_CALL_1(bpf_tcp_sock, struct sock *, sk)
 {
-	if (sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP)
+	if (sk_fullsock(sk) && sk_is_tcp(sk))
 		return (unsigned long)sk;
 
 	return (unsigned long)NULL;
-- 
2.54.0.545.g6539524ca2-goog

[PATCH v2 bpf 2/6] selftest: bpf: Add test for bpf_tcp_sock() and RAW socket.

[Kuniyuki Iwashima]

Let's extend sockopt_sk.c to cover bpf_tcp_sock() for the
wrong socket type.

Before:
  # ./test_progs -t sockopt_sk
  [  151.948613] ==================================================================
  [  151.951376] BUG: KASAN: slab-out-of-bounds in sol_tcp_sockopt+0xc7/0x8e0
  [  151.954159] Read of size 8 at addr ffff88801083d760 by task test_progs/1259
  ...
  run_test:FAIL:getsetsockopt unexpected error: -1 (errno 0)
  #427     sockopt_sk:FAIL

After:
  #427     sockopt_sk:OK

While at it, missing free() is fixed up.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
v2: Inverted if (err) to if (!err)
---
 .../selftests/bpf/prog_tests/sockopt_sk.c      | 18 +++++++++++++++++-
 tools/testing/selftests/bpf/progs/sockopt_sk.c | 16 ++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c b/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c
index 53637431ec5d..5fd33ad2eaaf 100644
--- a/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c
+++ b/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c
@@ -190,7 +190,7 @@ static int getsetsockopt(void)
 	fd = socket(AF_NETLINK, SOCK_RAW, 0);
 	if (fd < 0) {
 		log_err("Failed to create AF_NETLINK socket");
-		return -1;
+		goto err;
 	}
 
 	buf.u32 = 1;
@@ -211,6 +211,22 @@ static int getsetsockopt(void)
 	}
 	ASSERT_EQ(optlen, 8, "Unexpected NETLINK_LIST_MEMBERSHIPS value");
 
+	/* Trick bpf_tcp_sock() with IPPROTO_TCP */
+	close(fd);
+	fd = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
+	if (fd < 0) {
+		log_err("Failed to create RAW socket");
+		goto err;
+	}
+
+	optlen = 20;
+	errno = 0;
+	err = setsockopt(fd, SOL_TCP, TCP_SAVED_SYN, &buf, optlen);
+	if (!err) {
+		log_err("Unexpected setsockopt(TCP_SAVED_SYN)");
+		goto err;
+	}
+
 	free(big_buf);
 	close(fd);
 	return 0;
diff --git a/tools/testing/selftests/bpf/progs/sockopt_sk.c b/tools/testing/selftests/bpf/progs/sockopt_sk.c
index cb990a7d3d45..5e0b27e7855c 100644
--- a/tools/testing/selftests/bpf/progs/sockopt_sk.c
+++ b/tools/testing/selftests/bpf/progs/sockopt_sk.c
@@ -149,6 +149,20 @@ int _setsockopt(struct bpf_sockopt *ctx)
 	if (sk && sk->family == AF_NETLINK)
 		goto out;
 
+	if (sk && sk->family == AF_INET && sk->type == SOCK_RAW) {
+		struct bpf_tcp_sock *tp = bpf_tcp_sock(sk);
+
+		if (tp) {
+			char saved_syn[60];
+
+			bpf_getsockopt(sk, SOL_TCP, TCP_SAVED_SYN,
+				       &saved_syn, sizeof(saved_syn));
+			goto consumed;
+		}
+
+		goto out;
+	}
+
 	/* Make sure bpf_get_netns_cookie is callable.
 	 */
 	if (bpf_get_netns_cookie(NULL) == 0)
@@ -224,6 +238,8 @@ int _setsockopt(struct bpf_sockopt *ctx)
 		return 0; /* couldn't get sk storage */
 
 	storage->val = optval[0];
+
+consumed:
 	ctx->optlen = -1; /* BPF has consumed this option, don't call kernel
 			   * setsockopt handler.
 			   */
-- 
2.54.0.545.g6539524ca2-goog

[PATCH v2 bpf 3/6] mptcp: bpf: fix type confusion in bpf_mptcp_sock_from_subflow()

[Kuniyuki Iwashima]

From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>

bpf_mptcp_sock_from_subflow() only checks if sk->sk_protocol is
IPPROTO_TCP, but RAW socket can bypass it:

  socket(AF_INET, SOCK_RAW, IPPROTO_TCP)

In this case, it would NOT be valid to call sk_is_mptcp() which will
assume sk is a pointer to a struct tcp_sock, and wrongly checks for:
tcp_sk(sk)->is_mptcp.

Fixes: 3bc253c2e652 ("bpf: Add bpf_skc_to_mptcp_sock_proto")
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
v1: https://lore.kernel.org/mptcp/20260430-mptcp-bpf-mptcp-sock-type-v1-1-d2ed5cda7da9@kernel.org/
---
 net/mptcp/bpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c
index 8a16672b94e2..4cc16cbeb328 100644
--- a/net/mptcp/bpf.c
+++ b/net/mptcp/bpf.c
@@ -14,7 +14,7 @@
 
 struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk)
 {
-	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP && sk_is_mptcp(sk))
+	if (sk && sk_fullsock(sk) && sk_is_tcp(sk) && sk_is_mptcp(sk))
 		return mptcp_sk(mptcp_subflow_ctx(sk)->conn);
 
 	return NULL;
-- 
2.54.0.545.g6539524ca2-goog

[PATCH v2 bpf 4/6] bpf: tcp: Fix type confusion in bpf_skc_to_tcp_sock().

[Kuniyuki Iwashima]

bpf_skc_to_tcp_sock() only checks if sk->sk_protocol is
IPPROTO_TCP, but RAW socket can bypass it:

  socket(AF_INET, SOCK_RAW, IPPROTO_TCP)

Let's use sk_is_tcp().

Fixes: 478cfbdf5f13 ("bpf: Add bpf_skc_to_{tcp, tcp_timewait, tcp_request}_sock() helpers")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index cd88633f8dc1..7d945dc2cb92 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -11963,7 +11963,7 @@ const struct bpf_func_proto bpf_skc_to_tcp6_sock_proto = {
 
 BPF_CALL_1(bpf_skc_to_tcp_sock, struct sock *, sk)
 {
-	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP)
+	if (sk && sk_fullsock(sk) && sk_is_tcp(sk))
 		return (unsigned long)sk;
 
 	return (unsigned long)NULL;
-- 
2.54.0.545.g6539524ca2-goog

[PATCH v2 bpf 5/6] bpf: tcp: Fix type confusion in bpf_skc_to_tcp6_sock().

[Kuniyuki Iwashima]

bpf_skc_to_tcp6_sock() only checks if sk->sk_protocol is IPPROTO_TCP
and sk->sk_family is AF_INET6, but RAW socket can bypass it:

  socket(AF_INET6, SOCK_RAW, IPPROTO_TCP)

Let's check sk->sk_type too.

Fixes: af7ec1383361 ("bpf: Add bpf_skc_to_tcp6_sock() helper")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 7d945dc2cb92..684922efd481 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -11947,7 +11947,7 @@ BPF_CALL_1(bpf_skc_to_tcp6_sock, struct sock *, sk)
 	 */
 	BTF_TYPE_EMIT(struct tcp6_sock);
 	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP &&
-	    sk->sk_family == AF_INET6)
+	    sk->sk_type == SOCK_STREAM && sk->sk_family == AF_INET6)
 		return (unsigned long)sk;
 
 	return (unsigned long)NULL;
-- 
2.54.0.545.g6539524ca2-goog

[PATCH v2 bpf 6/6] bpf: tcp: Fix type confusion in sol_tcp_sockopt().

[Kuniyuki Iwashima]

sol_tcp_sockopt() only checks if sk->sk_protocol is IPPROTO_TCP,
but RAW socket can bypass it:

  socket(AF_INET, SOCK_RAW, IPPROTO_TCP)

Let's use sk_is_tcp().

Note that initially sol_tcp_sockopt() checked sk->sk_prot->setsockopt.

Fixes: 2ab42c7b871f ("bpf: Check the protocol of a sock to agree the calls to bpf_setsockopt().")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 684922efd481..ef0877eefaa7 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5481,7 +5481,7 @@ static int sol_tcp_sockopt(struct sock *sk, int optname,
 			   char *optval, int *optlen,
 			   bool getopt)
 {
-	if (sk->sk_protocol != IPPROTO_TCP)
+	if (!sk_is_tcp(sk))
 		return -EINVAL;
 
 	switch (optname) {
-- 
2.54.0.545.g6539524ca2-goog

Re: [PATCH v2 bpf 1/6] bpf: tcp: Fix type confusion in bpf_tcp_sock().

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 3247 bytes --]

> diff --git a/net/core/filter.c b/net/core/filter.c
> index bc96c18df4e0..cd88633f8dc1 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -7475,7 +7475,7 @@ u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
>
>  BPF_CALL_1(bpf_tcp_sock, struct sock *, sk)
>  {
> -	if (sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP)
> +	if (sk_fullsock(sk) && sk_is_tcp(sk))
>  		return (unsigned long)sk;
>
>  	return (unsigned long)NULL;

While this patch fixes bpf_tcp_sock(), does sol_tcp_sockopt() remain
vulnerable? Since ctx->sk evaluates to PTR_TO_SOCKET in a CGROUP_SOCKOPT
program and is directly accepted by bpf_setsockopt() and bpf_getsockopt()
via ARG_PTR_TO_BTF_ID_SOCK_COMMON, can a user create a RAW socket with
IPPROTO_TCP and directly pass ctx->sk to bpf_setsockopt(), bypassing
bpf_tcp_sock() entirely?

Looking at sol_tcp_sockopt():

static int sol_tcp_sockopt(struct sock *sk, int optname,
			   char *optval, int *optlen,
			   bool getopt)
{
	if (sk->sk_protocol != IPPROTO_TCP)
		return -EINVAL;

This appears to only check sk->sk_protocol == IPPROTO_TCP without verifying
sk->sk_type == SOCK_STREAM, which would allow the same slab out-of-bounds
access through a different code path.

Additionally, do bpf_skc_to_tcp_sock() and bpf_skc_to_tcp6_sock() suffer
from the same type confusion? They appear to check sk->sk_protocol ==
IPPROTO_TCP without verifying sk->sk_type == SOCK_STREAM.

Could a BPF program pass a RAW socket with IPPROTO_TCP to these helpers
and receive a valid BTF pointer to struct tcp_sock, allowing out-of-bounds
slab reads?

Looking at bpf_skc_to_tcp_sock():

BPF_CALL_1(bpf_skc_to_tcp_sock, struct sock *, sk)
{
	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP)
		return (unsigned long)sk;

	return (unsigned long)NULL;
}

And bpf_skc_to_tcp6_sock():

BPF_CALL_1(bpf_skc_to_tcp6_sock, struct sock *, sk)
{
	/* tcp6_sock type is not generated in dwarf and hence btf,
	 * trigger an explicit type generation here.
	 */
	BTF_TYPE_EMIT(struct tcp6_sock);
	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP &&
	    sk->sk_family == AF_INET6)
		return (unsigned long)sk;

Finally, does bpf_mptcp_sock_from_subflow() in net/mptcp/bpf.c also need
a similar update? It checks sk->sk_protocol == IPPROTO_TCP and immediately
evaluates sk_is_mptcp(sk).

Since sk_is_mptcp() indiscriminately casts the socket to struct tcp_sock
and accesses tcp_sk(sk)->is_mptcp, passing a RAW socket could trigger an
immediate out-of-bounds slab read. If this memory happens to be non-zero,
it might proceed to call mptcp_subflow_ctx(sk)->conn, which would read a
garbage pointer from out-of-bounds memory:

struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk)
{
	if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP && sk_is_mptcp(sk))
		return mptcp_sk(mptcp_subflow_ctx(sk)->conn);

	return NULL;
}

These issues were raised by sashiko-bot@kernel.org in v1:
https://lore.kernel.org/bpf/20260501184452.7F46FC2BCB4@smtp.kernel.org/


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25344293379

Re: [PATCH v2 bpf 1/6] bpf: tcp: Fix type confusion in bpf_tcp_sock().

[Kuniyuki Iwashima]

On Mon, May 4, 2026 at 2:50 PM <bot+bpf-ci@kernel.org> wrote:
>
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index bc96c18df4e0..cd88633f8dc1 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -7475,7 +7475,7 @@ u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
> >
> >  BPF_CALL_1(bpf_tcp_sock, struct sock *, sk)
> >  {
> > -     if (sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP)
> > +     if (sk_fullsock(sk) && sk_is_tcp(sk))
> >               return (unsigned long)sk;
> >
> >       return (unsigned long)NULL;
>
> While this patch fixes bpf_tcp_sock(), does sol_tcp_sockopt() remain

It seems Sashiko does not have context on the following patches.

All helper functions mentioned in the review comment are fixed
in the later patches separately.



> vulnerable? Since ctx->sk evaluates to PTR_TO_SOCKET in a CGROUP_SOCKOPT
> program and is directly accepted by bpf_setsockopt() and bpf_getsockopt()
> via ARG_PTR_TO_BTF_ID_SOCK_COMMON, can a user create a RAW socket with
> IPPROTO_TCP and directly pass ctx->sk to bpf_setsockopt(), bypassing
> bpf_tcp_sock() entirely?
>
> Looking at sol_tcp_sockopt():
>
> static int sol_tcp_sockopt(struct sock *sk, int optname,
>                            char *optval, int *optlen,
>                            bool getopt)
> {
>         if (sk->sk_protocol != IPPROTO_TCP)
>                 return -EINVAL;
>
> This appears to only check sk->sk_protocol == IPPROTO_TCP without verifying
> sk->sk_type == SOCK_STREAM, which would allow the same slab out-of-bounds
> access through a different code path.
>
> Additionally, do bpf_skc_to_tcp_sock() and bpf_skc_to_tcp6_sock() suffer
> from the same type confusion? They appear to check sk->sk_protocol ==
> IPPROTO_TCP without verifying sk->sk_type == SOCK_STREAM.
>
> Could a BPF program pass a RAW socket with IPPROTO_TCP to these helpers
> and receive a valid BTF pointer to struct tcp_sock, allowing out-of-bounds
> slab reads?
>
> Looking at bpf_skc_to_tcp_sock():
>
> BPF_CALL_1(bpf_skc_to_tcp_sock, struct sock *, sk)
> {
>         if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP)
>                 return (unsigned long)sk;
>
>         return (unsigned long)NULL;
> }
>
> And bpf_skc_to_tcp6_sock():
>
> BPF_CALL_1(bpf_skc_to_tcp6_sock, struct sock *, sk)
> {
>         /* tcp6_sock type is not generated in dwarf and hence btf,
>          * trigger an explicit type generation here.
>          */
>         BTF_TYPE_EMIT(struct tcp6_sock);
>         if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP &&
>             sk->sk_family == AF_INET6)
>                 return (unsigned long)sk;
>
> Finally, does bpf_mptcp_sock_from_subflow() in net/mptcp/bpf.c also need
> a similar update? It checks sk->sk_protocol == IPPROTO_TCP and immediately
> evaluates sk_is_mptcp(sk).
>
> Since sk_is_mptcp() indiscriminately casts the socket to struct tcp_sock
> and accesses tcp_sk(sk)->is_mptcp, passing a RAW socket could trigger an
> immediate out-of-bounds slab read. If this memory happens to be non-zero,
> it might proceed to call mptcp_subflow_ctx(sk)->conn, which would read a
> garbage pointer from out-of-bounds memory:
>
> struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk)
> {
>         if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP && sk_is_mptcp(sk))
>                 return mptcp_sk(mptcp_subflow_ctx(sk)->conn);
>
>         return NULL;
> }
>
> These issues were raised by sashiko-bot@kernel.org in v1:
> https://lore.kernel.org/bpf/20260501184452.7F46FC2BCB4@smtp.kernel.org/
>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25344293379