FAILED: patch "[PATCH] mptcp: pm: avoid possible UaF when selecting endp" failed to apply to 6.1-stable tree

FAILED: patch "[PATCH] mptcp: pm: avoid possible UaF when selecting endp" failed to apply to 6.1-stable tree

[gregkh]

The patch below does not apply to the 6.1-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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 48e50dcbcbaaf713d82bf2da5c16aeced94ad07d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024082656-bamboo-skinless-9366@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

48e50dcbcbaa ("mptcp: pm: avoid possible UaF when selecting endp")
85df533a787b ("mptcp: pm: do not ignore 'subflow' if 'signal' flag is also set")
cd7c957f936f ("mptcp: pm: don't try to create sf if alloc failed")
c95eb32ced82 ("mptcp: pm: reduce indentation blocks")
528cb5f2a1e8 ("mptcp: pass addr to mptcp_pm_alloc_anno_list")
77e4b94a3de6 ("mptcp: update userspace pm infos")
24430f8bf516 ("mptcp: add address into userspace pm list")
b9d69db87fb7 ("mptcp: let the in-kernel PM use mixed IPv4 and IPv6 addresses")
fb00ee4f3343 ("mptcp: netlink: respect v4/v6-only sockets")
80638684e840 ("mptcp: get sk from msk directly")

thanks,

greg k-h

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

From 48e50dcbcbaaf713d82bf2da5c16aeced94ad07d Mon Sep 17 00:00:00 2001
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Mon, 19 Aug 2024 21:45:32 +0200
Subject: [PATCH] mptcp: pm: avoid possible UaF when selecting endp

select_local_address() and select_signal_address() both select an
endpoint entry from the list inside an RCU protected section, but return
a reference to it, to be read later on. If the entry is dereferenced
after the RCU unlock, reading info could cause a Use-after-Free.

A simple solution is to copy the required info while inside the RCU
protected section to avoid any risk of UaF later. The address ID might
need to be modified later to handle the ID0 case later, so a copy seems
OK to deal with.

Reported-by: Paolo Abeni <pabeni@redhat.com>
Closes: https://lore.kernel.org/45cd30d3-7710-491c-ae4d-a1368c00beb1@redhat.com
Fixes: 01cacb00b35c ("mptcp: add netlink-based PM")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20240819-net-mptcp-pm-reusing-id-v1-14-38035d40de5b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index a2e37ab1c40f..3e4ad801786f 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -143,11 +143,13 @@ static bool lookup_subflow_by_daddr(const struct list_head *list,
 	return false;
 }
 
-static struct mptcp_pm_addr_entry *
+static bool
 select_local_address(const struct pm_nl_pernet *pernet,
-		     const struct mptcp_sock *msk)
+		     const struct mptcp_sock *msk,
+		     struct mptcp_pm_addr_entry *new_entry)
 {
-	struct mptcp_pm_addr_entry *entry, *ret = NULL;
+	struct mptcp_pm_addr_entry *entry;
+	bool found = false;
 
 	msk_owned_by_me(msk);
 
@@ -159,17 +161,21 @@ select_local_address(const struct pm_nl_pernet *pernet,
 		if (!test_bit(entry->addr.id, msk->pm.id_avail_bitmap))
 			continue;
 
-		ret = entry;
+		*new_entry = *entry;
+		found = true;
 		break;
 	}
 	rcu_read_unlock();
-	return ret;
+
+	return found;
 }
 
-static struct mptcp_pm_addr_entry *
-select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk)
+static bool
+select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk,
+		      struct mptcp_pm_addr_entry *new_entry)
 {
-	struct mptcp_pm_addr_entry *entry, *ret = NULL;
+	struct mptcp_pm_addr_entry *entry;
+	bool found = false;
 
 	rcu_read_lock();
 	/* do not keep any additional per socket state, just signal
@@ -184,11 +190,13 @@ select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk)
 		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL))
 			continue;
 
-		ret = entry;
+		*new_entry = *entry;
+		found = true;
 		break;
 	}
 	rcu_read_unlock();
-	return ret;
+
+	return found;
 }
 
 unsigned int mptcp_pm_get_add_addr_signal_max(const struct mptcp_sock *msk)
@@ -512,9 +520,10 @@ __lookup_addr(struct pm_nl_pernet *pernet, const struct mptcp_addr_info *info)
 
 static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 {
-	struct mptcp_pm_addr_entry *local, *signal_and_subflow = NULL;
 	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_addr_entry local;
 	unsigned int add_addr_signal_max;
+	bool signal_and_subflow = false;
 	unsigned int local_addr_max;
 	struct pm_nl_pernet *pernet;
 	unsigned int subflows_max;
@@ -565,23 +574,22 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 		if (msk->pm.addr_signal & BIT(MPTCP_ADD_ADDR_SIGNAL))
 			return;
 
-		local = select_signal_address(pernet, msk);
-		if (!local)
+		if (!select_signal_address(pernet, msk, &local))
 			goto subflow;
 
 		/* If the alloc fails, we are on memory pressure, not worth
 		 * continuing, and trying to create subflows.
 		 */
-		if (!mptcp_pm_alloc_anno_list(msk, &local->addr))
+		if (!mptcp_pm_alloc_anno_list(msk, &local.addr))
 			return;
 
-		__clear_bit(local->addr.id, msk->pm.id_avail_bitmap);
+		__clear_bit(local.addr.id, msk->pm.id_avail_bitmap);
 		msk->pm.add_addr_signaled++;
-		mptcp_pm_announce_addr(msk, &local->addr, false);
+		mptcp_pm_announce_addr(msk, &local.addr, false);
 		mptcp_pm_nl_addr_send_ack(msk);
 
-		if (local->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
-			signal_and_subflow = local;
+		if (local.flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
+			signal_and_subflow = true;
 	}
 
 subflow:
@@ -592,26 +600,22 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 		bool fullmesh;
 		int i, nr;
 
-		if (signal_and_subflow) {
-			local = signal_and_subflow;
-			signal_and_subflow = NULL;
-		} else {
-			local = select_local_address(pernet, msk);
-			if (!local)
-				break;
-		}
+		if (signal_and_subflow)
+			signal_and_subflow = false;
+		else if (!select_local_address(pernet, msk, &local))
+			break;
 
-		fullmesh = !!(local->flags & MPTCP_PM_ADDR_FLAG_FULLMESH);
+		fullmesh = !!(local.flags & MPTCP_PM_ADDR_FLAG_FULLMESH);
 
 		msk->pm.local_addr_used++;
-		__clear_bit(local->addr.id, msk->pm.id_avail_bitmap);
-		nr = fill_remote_addresses_vec(msk, &local->addr, fullmesh, addrs);
+		__clear_bit(local.addr.id, msk->pm.id_avail_bitmap);
+		nr = fill_remote_addresses_vec(msk, &local.addr, fullmesh, addrs);
 		if (nr == 0)
 			continue;
 
 		spin_unlock_bh(&msk->pm.lock);
 		for (i = 0; i < nr; i++)
-			__mptcp_subflow_connect(sk, &local->addr, &addrs[i]);
+			__mptcp_subflow_connect(sk, &local.addr, &addrs[i]);
 		spin_lock_bh(&msk->pm.lock);
 	}
 	mptcp_pm_nl_check_work_pending(msk);

[PATCH 6.1.y] mptcp: pm: avoid possible UaF when selecting endp

[Matthieu Baerts (NGI0)]

commit 48e50dcbcbaaf713d82bf2da5c16aeced94ad07d upstream.

select_local_address() and select_signal_address() both select an
endpoint entry from the list inside an RCU protected section, but return
a reference to it, to be read later on. If the entry is dereferenced
after the RCU unlock, reading info could cause a Use-after-Free.

A simple solution is to copy the required info while inside the RCU
protected section to avoid any risk of UaF later. The address ID might
need to be modified later to handle the ID0 case later, so a copy seems
OK to deal with.

Reported-by: Paolo Abeni <pabeni@redhat.com>
Closes: https://lore.kernel.org/45cd30d3-7710-491c-ae4d-a1368c00beb1@redhat.com
Fixes: 01cacb00b35c ("mptcp: add netlink-based PM")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20240819-net-mptcp-pm-reusing-id-v1-14-38035d40de5b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Conflicts in pm_netlink.c, because the context has been modified in
  commit b9d69db87fb7 ("mptcp: let the in-kernel PM use mixed IPv4 and
  IPv6 addresses"), which is not a candidate for the backports. The same
  modifications have been applied in this version. The conflict in
  mptcp_pm_create_subflow_or_signal_addr() has been resolved by taking
  the newer version, which skip a lock if it is not needed. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_netlink.c | 68 +++++++++++++++++++++++-------------------
 1 file changed, 37 insertions(+), 31 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index a152a3474d2c..44b036abe30f 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -150,12 +150,14 @@ static bool lookup_subflow_by_daddr(const struct list_head *list,
 	return false;
 }
 
-static struct mptcp_pm_addr_entry *
+static bool
 select_local_address(const struct pm_nl_pernet *pernet,
-		     const struct mptcp_sock *msk)
+		     const struct mptcp_sock *msk,
+		     struct mptcp_pm_addr_entry *new_entry)
 {
 	const struct sock *sk = (const struct sock *)msk;
-	struct mptcp_pm_addr_entry *entry, *ret = NULL;
+	struct mptcp_pm_addr_entry *entry;
+	bool found = false;
 
 	msk_owned_by_me(msk);
 
@@ -177,17 +179,21 @@ select_local_address(const struct pm_nl_pernet *pernet,
 				continue;
 		}
 
-		ret = entry;
+		*new_entry = *entry;
+		found = true;
 		break;
 	}
 	rcu_read_unlock();
-	return ret;
+
+	return found;
 }
 
-static struct mptcp_pm_addr_entry *
-select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk)
+static bool
+select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk,
+		      struct mptcp_pm_addr_entry *new_entry)
 {
-	struct mptcp_pm_addr_entry *entry, *ret = NULL;
+	struct mptcp_pm_addr_entry *entry;
+	bool found = false;
 
 	rcu_read_lock();
 	/* do not keep any additional per socket state, just signal
@@ -202,11 +208,13 @@ select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk)
 		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL))
 			continue;
 
-		ret = entry;
+		*new_entry = *entry;
+		found = true;
 		break;
 	}
 	rcu_read_unlock();
-	return ret;
+
+	return found;
 }
 
 unsigned int mptcp_pm_get_add_addr_signal_max(const struct mptcp_sock *msk)
@@ -527,9 +535,10 @@ __lookup_addr(struct pm_nl_pernet *pernet, const struct mptcp_addr_info *info,
 
 static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 {
-	struct mptcp_pm_addr_entry *local, *signal_and_subflow = NULL;
 	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_addr_entry local;
 	unsigned int add_addr_signal_max;
+	bool signal_and_subflow = false;
 	unsigned int local_addr_max;
 	struct pm_nl_pernet *pernet;
 	unsigned int subflows_max;
@@ -580,23 +589,22 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 		if (msk->pm.addr_signal & BIT(MPTCP_ADD_ADDR_SIGNAL))
 			return;
 
-		local = select_signal_address(pernet, msk);
-		if (!local)
+		if (!select_signal_address(pernet, msk, &local))
 			goto subflow;
 
 		/* If the alloc fails, we are on memory pressure, not worth
 		 * continuing, and trying to create subflows.
 		 */
-		if (!mptcp_pm_alloc_anno_list(msk, &local->addr))
+		if (!mptcp_pm_alloc_anno_list(msk, &local.addr))
 			return;
 
-		__clear_bit(local->addr.id, msk->pm.id_avail_bitmap);
+		__clear_bit(local.addr.id, msk->pm.id_avail_bitmap);
 		msk->pm.add_addr_signaled++;
-		mptcp_pm_announce_addr(msk, &local->addr, false);
+		mptcp_pm_announce_addr(msk, &local.addr, false);
 		mptcp_pm_nl_addr_send_ack(msk);
 
-		if (local->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
-			signal_and_subflow = local;
+		if (local.flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
+			signal_and_subflow = true;
 	}
 
 subflow:
@@ -607,24 +615,22 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 		bool fullmesh;
 		int i, nr;
 
-		if (signal_and_subflow) {
-			local = signal_and_subflow;
-			signal_and_subflow = NULL;
-		} else {
-			local = select_local_address(pernet, msk);
-			if (!local)
-				break;
-		}
+		if (signal_and_subflow)
+			signal_and_subflow = false;
+		else if (!select_local_address(pernet, msk, &local))
+			break;
 
-		fullmesh = !!(local->flags & MPTCP_PM_ADDR_FLAG_FULLMESH);
+		fullmesh = !!(local.flags & MPTCP_PM_ADDR_FLAG_FULLMESH);
 
 		msk->pm.local_addr_used++;
-		nr = fill_remote_addresses_vec(msk, &local->addr, fullmesh, addrs);
-		if (nr)
-			__clear_bit(local->addr.id, msk->pm.id_avail_bitmap);
+		__clear_bit(local.addr.id, msk->pm.id_avail_bitmap);
+		nr = fill_remote_addresses_vec(msk, &local.addr, fullmesh, addrs);
+		if (nr == 0)
+			continue;
+
 		spin_unlock_bh(&msk->pm.lock);
 		for (i = 0; i < nr; i++)
-			__mptcp_subflow_connect(sk, &local->addr, &addrs[i]);
+			__mptcp_subflow_connect(sk, &local.addr, &addrs[i]);
 		spin_lock_bh(&msk->pm.lock);
 	}
 	mptcp_pm_nl_check_work_pending(msk);
-- 
2.45.2

[PATCH 6.1.y 0/2] Backport of "mptcp: pm: reuse ID 0 after delete and re-add" and more

[Matthieu Baerts (NGI0)]

After having applied the patch "mptcp: pm: avoid possible UaF when
selecting endp" in v6.1 with the adaptations proposed in the parent
message [1], the two following patches can be applied without conflicts:

- 8b8ed1b429f8 ("mptcp: pm: reuse ID 0 after delete and re-add")
- 9366922adc6a ("mptcp: pm: fix ID 0 endp usage after multiple re-creations")

[1] https://lore.kernel.org/20240904105721.4075460-2-matttbe@kernel.org

Matthieu Baerts (NGI0) (2):
  mptcp: pm: reuse ID 0 after delete and re-add
  mptcp: pm: fix ID 0 endp usage after multiple re-creations

 net/mptcp/pm_netlink.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

-- 
2.45.2

[PATCH 6.1.y 1/2] mptcp: pm: reuse ID 0 after delete and re-add

[Matthieu Baerts (NGI0)]

commit 8b8ed1b429f8fa7ebd5632555e7b047bc0620075 upstream.

When the endpoint used by the initial subflow is removed and re-added
later, the PM has to force the ID 0, it is a special case imposed by the
MPTCP specs.

Note that the endpoint should then need to be re-added reusing the same
ID.

Fixes: 3ad14f54bd74 ("mptcp: more accurate MPC endpoint tracking")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_netlink.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 44b036abe30f..c834de47bddc 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -600,6 +600,11 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 
 		__clear_bit(local.addr.id, msk->pm.id_avail_bitmap);
 		msk->pm.add_addr_signaled++;
+
+		/* Special case for ID0: set the correct ID */
+		if (local.addr.id == msk->mpc_endpoint_id)
+			local.addr.id = 0;
+
 		mptcp_pm_announce_addr(msk, &local.addr, false);
 		mptcp_pm_nl_addr_send_ack(msk);
 
@@ -624,6 +629,11 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 
 		msk->pm.local_addr_used++;
 		__clear_bit(local.addr.id, msk->pm.id_avail_bitmap);
+
+		/* Special case for ID0: set the correct ID */
+		if (local.addr.id == msk->mpc_endpoint_id)
+			local.addr.id = 0;
+
 		nr = fill_remote_addresses_vec(msk, &local.addr, fullmesh, addrs);
 		if (nr == 0)
 			continue;
-- 
2.45.2

[PATCH 6.1.y 2/2] mptcp: pm: fix ID 0 endp usage after multiple re-creations

[Matthieu Baerts (NGI0)]

commit 9366922adc6a71378ca01f898c41be295309f044 upstream.

'local_addr_used' and 'add_addr_accepted' are decremented for addresses
not related to the initial subflow (ID0), because the source and
destination addresses of the initial subflows are known from the
beginning: they don't count as "additional local address being used" or
"ADD_ADDR being accepted".

It is then required not to increment them when the entrypoint used by
the initial subflow is removed and re-added during a connection. Without
this modification, this entrypoint cannot be removed and re-added more
than once.

Reported-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/512
Fixes: 3ad14f54bd74 ("mptcp: more accurate MPC endpoint tracking")
Reported-by: syzbot+455d38ecd5f655fc45cf@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/00000000000049861306209237f4@google.com
Cc: stable@vger.kernel.org
Tested-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_netlink.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index c834de47bddc..2f8a13589ed6 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -627,12 +627,13 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 
 		fullmesh = !!(local.flags & MPTCP_PM_ADDR_FLAG_FULLMESH);
 
-		msk->pm.local_addr_used++;
 		__clear_bit(local.addr.id, msk->pm.id_avail_bitmap);
 
 		/* Special case for ID0: set the correct ID */
 		if (local.addr.id == msk->mpc_endpoint_id)
 			local.addr.id = 0;
+		else /* local_addr_used is not decr for ID 0 */
+			msk->pm.local_addr_used++;
 
 		nr = fill_remote_addresses_vec(msk, &local.addr, fullmesh, addrs);
 		if (nr == 0)
@@ -758,7 +759,9 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 	spin_lock_bh(&msk->pm.lock);
 
 	if (sf_created) {
-		msk->pm.add_addr_accepted++;
+		/* add_addr_accepted is not decr for ID 0 */
+		if (remote.id)
+			msk->pm.add_addr_accepted++;
 		if (msk->pm.add_addr_accepted >= add_addr_accept_max ||
 		    msk->pm.subflows >= subflows_max)
 			WRITE_ONCE(msk->pm.accept_addr, false);
-- 
2.45.2

Re: [PATCH 6.1.y] mptcp: pm: avoid possible UaF when selecting endp

[Greg KH]

On Wed, Sep 04, 2024 at 12:57:22PM +0200, Matthieu Baerts (NGI0) wrote:
> commit 48e50dcbcbaaf713d82bf2da5c16aeced94ad07d upstream.
> 

Applied

Re: [PATCH 6.1.y 2/2] mptcp: pm: fix ID 0 endp usage after multiple re-creations

[Greg KH]

On Wed, Sep 04, 2024 at 01:03:09PM +0200, Matthieu Baerts (NGI0) wrote:
> commit 9366922adc6a71378ca01f898c41be295309f044 upstream.
> 

Applied

Re: [PATCH 6.1.y 1/2] mptcp: pm: reuse ID 0 after delete and re-add

[Greg KH]

On Wed, Sep 04, 2024 at 01:03:08PM +0200, Matthieu Baerts (NGI0) wrote:
> commit 8b8ed1b429f8fa7ebd5632555e7b047bc0620075 upstream.
> 

Applied