FAILED: patch "[PATCH] mptcp: pm: userspace: fix address ID overflow" failed to apply to 6.6-stable tree

FAILED: patch "[PATCH] mptcp: pm: userspace: fix address ID overflow" failed to apply to 6.6-stable tree

[gregkh]

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x f9f0068e8813d8c10d016b030fc3a320d0b6767c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026091627-sleep-poem-4828@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f9f0068e8813d8c10d016b030fc3a320d0b6767c Mon Sep 17 00:00:00 2001
From: Qing Luo <luoqing@kylinos.cn>
Date: Tue, 8 Sep 2026 16:07:13 +0200
Subject: [PATCH] mptcp: pm: userspace: fix address ID overflow

When all MPTCP address IDs (1-255) are exhausted in the userspace PM,
find_next_zero_bit() returns MPTCP_PM_MAX_ADDR_ID + 1 (256). This value
overflows when stored in the u8 field e->addr.id, resulting in ID 0
being stored and the entry being incorrectly added to the list.

ID 0 is reserved for the initial connection in MPTCP, so this overflow
can cause address conflicts.

Note: the in-kernel PM already has an 'endpoints == MPTCP_PM_MAX_ADDR_ID'
check in mptcp_pm_nl_append_new_local_addr() that returns -ERANGE before
reaching find_next_zero_bit(), preventing this overflow. So this fix only
addresses the userspace PM path.

Check the find_next_zero_bit() result against MPTCP_PM_MAX_ADDR_ID and
return -ENOSPC if all IDs are truly exhausted. Move the ID allocation
check before the memory allocation so that the error path does not need
to free the allocated entry.

Fixes: 4638de5aefe5 ("mptcp: handle local addrs announced by userspace PMs")
Cc: stable@vger.kernel.org
Signed-off-by: Qing Luo <luoqing@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260908-net-mptcp-misc-fixes-7-3-rc1-v2-8-df1de70348b6@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index b94fbb483bf9..fab16d953dbf 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -69,6 +69,19 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
 	}
 
 	if (!addr_match && !id_match) {
+		unsigned int id;
+
+		if (!entry->addr.id && needs_id) {
+			id = find_next_zero_bit(id_bitmap,
+						MPTCP_PM_MAX_ADDR_ID + 1, 1);
+			if (id > MPTCP_PM_MAX_ADDR_ID) {
+				ret = -ENOSPC;
+				goto append_err;
+			}
+		} else {
+			id = entry->addr.id;
+		}
+
 		/* Memory for the entry is allocated from the
 		 * sock option buffer.
 		 */
@@ -78,10 +91,7 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
 			goto append_err;
 		}
 
-		if (!e->addr.id && needs_id)
-			e->addr.id = find_next_zero_bit(id_bitmap,
-							MPTCP_PM_MAX_ADDR_ID + 1,
-							1);
+		e->addr.id = id;
 		list_add_tail_rcu(&e->list, &msk->pm.userspace_pm_local_addr_list);
 		msk->pm.local_addr_used++;
 		ret = e->addr.id;

[PATCH 6.6.y 1/4] mptcp: pm: drop match in userspace_pm_append_new_local_addr

[Sasha Levin]

From: Geliang Tang <tanggeliang@kylinos.cn>

[ Upstream commit 640e3d69d0bc70d7d3de34800a1640793262bd08 ]

The variable 'match' in mptcp_userspace_pm_append_new_local_addr() is a
redundant one, and this patch drops it.

No need to define 'match' as 'struct mptcp_pm_addr_entry *' type. In this
function, it's only used to check whether it's NULL. It can be defined as
a Boolean one.

Also other variables 'addr_match' and 'id_match' make 'match' a redundant
one, which can be replaced by directly checking 'addr_match && id_match'.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250221-net-next-mptcp-pm-misc-cleanup-3-v1-5-2b70ab1cee79@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: f9f0068e8813 ("mptcp: pm: userspace: fix address ID overflow")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/mptcp/pm_userspace.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index 12dd30d63c717..bfcef17fe9dda 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -40,7 +40,6 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
 						    bool needs_id)
 {
 	DECLARE_BITMAP(id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
-	struct mptcp_pm_addr_entry *match = NULL;
 	struct sock *sk = (struct sock *)msk;
 	struct mptcp_pm_addr_entry *e;
 	bool addr_match = false;
@@ -59,16 +58,12 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
 		if (addr_match && entry->addr.id == 0 && needs_id)
 			entry->addr.id = e->addr.id;
 		id_match = (e->addr.id == entry->addr.id);
-		if (addr_match && id_match) {
-			match = e;
+		if (addr_match || id_match)
 			break;
-		} else if (addr_match || id_match) {
-			break;
-		}
 		__set_bit(e->addr.id, id_bitmap);
 	}
 
-	if (!match && !addr_match && !id_match) {
+	if (!addr_match && !id_match) {
 		/* Memory for the entry is allocated from the
 		 * sock option buffer.
 		 */
@@ -86,7 +81,7 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
 		list_add_tail_rcu(&e->list, &msk->pm.userspace_pm_local_addr_list);
 		msk->pm.local_addr_used++;
 		ret = e->addr.id;
-	} else if (match) {
+	} else if (addr_match && id_match) {
 		ret = entry->addr.id;
 	}
 
-- 
2.53.0

[PATCH 6.6.y 2/4] sock: add sock_kmemdup helper

[Sasha Levin]

From: Geliang Tang <tanggeliang@kylinos.cn>

[ Upstream commit 456cc675b6d4cadd4872a477d8976ff56eef4b6f ]

This patch adds the sock version of kmemdup() helper, named sock_kmemdup(),
to duplicate the input "src" memory block using the socket's option memory
buffer.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/f828077394c7d1f3560123497348b438c875b510.1740735165.git.tanggeliang@kylinos.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: f9f0068e8813 ("mptcp: pm: userspace: fix address ID overflow")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/net/sock.h |  2 ++
 net/core/sock.c    | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/net/sock.h b/include/net/sock.h
index c1f129a532b20..db10fd405dee6 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1955,6 +1955,8 @@ static inline struct sk_buff *sock_alloc_send_skb(struct sock *sk,
 }
 
 void *sock_kmalloc(struct sock *sk, int size, gfp_t priority);
+void *sock_kmemdup(struct sock *sk, const void *src,
+		   int size, gfp_t priority);
 void sock_kfree_s(struct sock *sk, void *mem, int size);
 void sock_kzfree_s(struct sock *sk, void *mem, int size);
 void sk_send_sigurg(struct sock *sk);
diff --git a/net/core/sock.c b/net/core/sock.c
index 2f82dc45f93ec..119ee87caedd1 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2736,6 +2736,22 @@ void *sock_kmalloc(struct sock *sk, int size, gfp_t priority)
 }
 EXPORT_SYMBOL(sock_kmalloc);
 
+/*
+ * Duplicate the input "src" memory block using the socket's
+ * option memory buffer.
+ */
+void *sock_kmemdup(struct sock *sk, const void *src,
+		   int size, gfp_t priority)
+{
+	void *mem;
+
+	mem = sock_kmalloc(sk, size, priority);
+	if (mem)
+		memcpy(mem, src, size);
+	return mem;
+}
+EXPORT_SYMBOL(sock_kmemdup);
+
 /* Free an option memory block. Note, we actually want the inline
  * here as this allows gcc to detect the nullify and fold away the
  * condition entirely.
-- 
2.53.0

[PATCH 6.6.y 3/4] mptcp: use sock_kmemdup for address entry

[Sasha Levin]

From: Geliang Tang <tanggeliang@kylinos.cn>

[ Upstream commit 52f83c0b5f857dbe24f66fc9a7f035523e9ffbc9 ]

Instead of using sock_kmalloc() to allocate an address
entry "e" and then immediately duplicate the input "entry"
to it, the newly added sock_kmemdup() helper can be used in
mptcp_userspace_pm_append_new_local_addr() to simplify the code.

More importantly, the code "*e = *entry;" that assigns "entry"
to "e" is not easy to implemented in BPF if we use the same code
to implement an append_new_local_addr() helper of a BFP path
manager. This patch avoids this type of memory assignment
operation.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Acked-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/3e5a307aed213038a87e44ff93b5793229b16279.1740735165.git.tanggeliang@kylinos.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: f9f0068e8813 ("mptcp: pm: userspace: fix address ID overflow")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/mptcp/pm_userspace.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index bfcef17fe9dda..493a4511a5398 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -67,13 +67,12 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
 		/* Memory for the entry is allocated from the
 		 * sock option buffer.
 		 */
-		e = sock_kmalloc(sk, sizeof(*e), GFP_ATOMIC);
+		e = sock_kmemdup(sk, entry, sizeof(*entry), GFP_ATOMIC);
 		if (!e) {
 			ret = -ENOMEM;
 			goto append_err;
 		}
 
-		*e = *entry;
 		if (!e->addr.id && needs_id)
 			e->addr.id = find_next_zero_bit(id_bitmap,
 							MPTCP_PM_MAX_ADDR_ID + 1,
-- 
2.53.0

[PATCH 6.6.y 4/4] mptcp: pm: userspace: fix address ID overflow

[Sasha Levin]

From: Qing Luo <luoqing@kylinos.cn>

[ Upstream commit f9f0068e8813d8c10d016b030fc3a320d0b6767c ]

When all MPTCP address IDs (1-255) are exhausted in the userspace PM,
find_next_zero_bit() returns MPTCP_PM_MAX_ADDR_ID + 1 (256). This value
overflows when stored in the u8 field e->addr.id, resulting in ID 0
being stored and the entry being incorrectly added to the list.

ID 0 is reserved for the initial connection in MPTCP, so this overflow
can cause address conflicts.

Note: the in-kernel PM already has an 'endpoints == MPTCP_PM_MAX_ADDR_ID'
check in mptcp_pm_nl_append_new_local_addr() that returns -ERANGE before
reaching find_next_zero_bit(), preventing this overflow. So this fix only
addresses the userspace PM path.

Check the find_next_zero_bit() result against MPTCP_PM_MAX_ADDR_ID and
return -ENOSPC if all IDs are truly exhausted. Move the ID allocation
check before the memory allocation so that the error path does not need
to free the allocated entry.

Fixes: 4638de5aefe5 ("mptcp: handle local addrs announced by userspace PMs")
Cc: stable@vger.kernel.org
Signed-off-by: Qing Luo <luoqing@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260908-net-mptcp-misc-fixes-7-3-rc1-v2-8-df1de70348b6@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/mptcp/pm_userspace.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index 493a4511a5398..335ef95da4034 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -64,6 +64,19 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
 	}
 
 	if (!addr_match && !id_match) {
+		unsigned int id;
+
+		if (!entry->addr.id && needs_id) {
+			id = find_next_zero_bit(id_bitmap,
+						MPTCP_PM_MAX_ADDR_ID + 1, 1);
+			if (id > MPTCP_PM_MAX_ADDR_ID) {
+				ret = -ENOSPC;
+				goto append_err;
+			}
+		} else {
+			id = entry->addr.id;
+		}
+
 		/* Memory for the entry is allocated from the
 		 * sock option buffer.
 		 */
@@ -73,10 +86,7 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
 			goto append_err;
 		}
 
-		if (!e->addr.id && needs_id)
-			e->addr.id = find_next_zero_bit(id_bitmap,
-							MPTCP_PM_MAX_ADDR_ID + 1,
-							1);
+		e->addr.id = id;
 		list_add_tail_rcu(&e->list, &msk->pm.userspace_pm_local_addr_list);
 		msk->pm.local_addr_used++;
 		ret = e->addr.id;
-- 
2.53.0