Unrated severityNVD Advisory· Published May 28, 2026
CVE-2026-46170
CVE-2026-46170
Description
In the Linux kernel, the following vulnerability has been resolved:
mptcp: pm: ADD_ADDR rtx: free sk if last
When an ADD_ADDR is retransmitted, the sk is held in sk_reset_timer(), and released at the end.
If at that moment, it was the last reference being held, the sk would not be freed. sock_put() should then be called instead of __sock_put().
But that's not enough: if it is the last reference, sock_put() will call sk_free(), which will end up calling sk_stop_timer_sync() on the same timer, and waiting indefinitely to finish. So it is needed to mark that the timer is done at the end of the timer handler when it has not been rescheduled, not to call sk_stop_timer_sync() on "itself".
Affected products
2Patches
68143a224785cmptcp: pm: ADD_ADDR rtx: free sk if last
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"Matthieu Baerts (NGI0)"Fixed in 7.0.7via kernel-cna
2 files changed · +36 −22
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 37e48381ddebe5..6e96abc830e86d 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -340,22 +341,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -373,8 +374,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -382,9 +384,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -447,6 +453,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -467,7 +474,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 37e48381ddebe5..6e96abc830e86d 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -340,22 +341,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -373,8 +374,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -382,9 +384,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -447,6 +453,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -467,7 +474,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
b7b9a4615697mptcp: pm: ADD_ADDR rtx: free sk if last
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"Matthieu Baerts (NGI0)"Fixed in 7.1-rc3via kernel-cna
2 files changed · +36 −22
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 2a01bf1b5bfdad..8899327e59a1da 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -327,22 +328,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -360,8 +361,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -369,9 +371,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -434,6 +440,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -454,7 +461,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 2a01bf1b5bfdad..8899327e59a1da 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -327,22 +328,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -360,8 +361,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -369,9 +371,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -434,6 +440,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -454,7 +461,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
b74ad2019865mptcp: pm: ADD_ADDR rtx: free sk if last
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"Matthieu Baerts (NGI0)"Fixed in 6.18.30via kernel-cna
2 files changed · +36 −22
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 4dcac6135fbfaf..a1edfb74f924f3 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -340,22 +341,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -373,8 +374,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -382,9 +384,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -447,6 +453,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -467,7 +474,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 4dcac6135fbfaf..a1edfb74f924f3 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -340,22 +341,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -373,8 +374,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -382,9 +384,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -447,6 +453,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -467,7 +474,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
b74ad2019865mptcp: pm: ADD_ADDR rtx: free sk if last
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git"Matthieu Baerts (NGI0)"via nvd-ref
2 files changed · +36 −22
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 4dcac6135fbfaf..a1edfb74f924f3 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -340,22 +341,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -373,8 +374,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -382,9 +384,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -447,6 +453,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -467,7 +474,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 4dcac6135fbfaf..a1edfb74f924f3 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -340,22 +341,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -373,8 +374,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -382,9 +384,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -447,6 +453,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -467,7 +474,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
8143a224785cmptcp: pm: ADD_ADDR rtx: free sk if last
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git"Matthieu Baerts (NGI0)"via nvd-ref
2 files changed · +36 −22
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 37e48381ddebe5..6e96abc830e86d 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -340,22 +341,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -373,8 +374,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -382,9 +384,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -447,6 +453,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -467,7 +474,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 37e48381ddebe5..6e96abc830e86d 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -340,22 +341,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -373,8 +374,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -382,9 +384,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -447,6 +453,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -467,7 +474,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
b7b9a4615697mptcp: pm: ADD_ADDR rtx: free sk if last
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git"Matthieu Baerts (NGI0)"via nvd-ref
2 files changed · +36 −22
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 2a01bf1b5bfdad..8899327e59a1da 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -327,22 +328,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -360,8 +361,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -369,9 +371,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -434,6 +440,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -454,7 +461,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
net/mptcp/pm.c+18 −11 modifieddiff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 2a01bf1b5bfdad..8899327e59a1da 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -16,6 +16,7 @@ struct mptcp_pm_add_entry { struct list_head list; struct mptcp_addr_info addr; u8 retrans_times; + bool timer_done; struct timer_list add_timer; struct mptcp_sock *sock; struct rcu_head rcu; @@ -327,22 +328,22 @@ static void mptcp_pm_add_timer(struct timer_list *timer) add_timer); struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; - unsigned int timeout; + unsigned int timeout = 0; pr_debug("msk=%p\n", msk); + bh_lock_sock(sk); if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE)) - goto exit; + goto out; - bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ - sk_reset_timer(sk, timer, jiffies + HZ / 20); + timeout = HZ / 20; goto out; } if (mptcp_pm_should_add_signal_addr(msk)) { - sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8); + timeout = TCP_RTO_MAX / 8; goto out; } @@ -360,8 +361,9 @@ static void mptcp_pm_add_timer(struct timer_list *timer) } if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) - sk_reset_timer(sk, timer, - jiffies + (timeout << entry->retrans_times)); + timeout <<= entry->retrans_times; + else + timeout = 0; spin_unlock_bh(&msk->pm.lock); @@ -369,9 +371,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer) mptcp_pm_subflow_established(msk); out: + if (timeout) + sk_reset_timer(sk, timer, jiffies + timeout); + else + /* if sock_put calls sk_free: avoid waiting for this timer */ + entry->timer_done = true; bh_unlock_sock(sk); -exit: - __sock_put(sk); + sock_put(sk); } struct mptcp_pm_add_entry * @@ -434,6 +440,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0); reset_timer: + add_entry->timer_done = false; timeout = mptcp_adjust_add_addr_timeout(msk); if (timeout) sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout); @@ -454,7 +461,8 @@ static void mptcp_pm_free_anno_list(struct mptcp_sock *msk) spin_unlock_bh(&msk->pm.lock); list_for_each_entry_safe(entry, tmp, &free_list, list) { - sk_stop_timer_sync(sk, &entry->add_timer); + if (!entry->timer_done) + sk_stop_timer_sync(sk, &entry->add_timer); kfree_rcu(entry, rcu); } } -- cgit 1.3-korg
Vulnerability mechanics
Root cause
"Use of `__sock_put()` instead of `sock_put()` in the ADD_ADDR retransmission timer handler prevents socket freeing when the last reference is dropped, and a missing `timer_done` flag causes a deadlock when `sk_free()` calls `sk_stop_timer_sync()` on the currently executing timer."
Attack vector
An attacker who can trigger MPTCP ADD_ADDR retransmissions (e.g., by causing timeouts on an MPTCP connection) can cause the kernel to hit a use-after-free or deadlock scenario. When the ADD_ADDR retransmission timer fires and the socket's reference count drops to zero, the old code used `__sock_put()` which does not free the socket when it is the last reference. Even if `sock_put()` were used, `sk_free()` would call `sk_stop_timer_sync()` on the same timer that is currently running, causing an indefinite wait. This is a local denial-of-service condition exploitable by any user capable of establishing MPTCP connections.
Affected code
The vulnerability is in `net/mptcp/pm.c` in the `mptcp_pm_add_timer()` function and the `mptcp_pm_free_anno_list()` function [patch_id=2898089]. The `mptcp_pm_add_entry` struct lacked a `timer_done` flag, and the timer handler used `__sock_put()` instead of `sock_put()`.
What the fix does
The patch makes two changes in `net/mptcp/pm.c` [patch_id=2898089]. First, it replaces `__sock_put(sk)` with `sock_put(sk)` so that the socket is actually freed when the last reference is dropped. Second, it adds a `timer_done` boolean field to `struct mptcp_pm_add_entry`; when the timer handler finishes without rescheduling (timeout == 0), it sets `timer_done = true`. In `mptcp_pm_free_anno_list()`, `sk_stop_timer_sync()` is only called if `timer_done` is false, preventing the deadlock where `sk_free()` would try to synchronously stop the timer that is already completing.
Preconditions
- networkThe attacker must be able to establish MPTCP connections and cause ADD_ADDR retransmission timeouts.
- configThe MPTCP path manager must have ADD_ADDR signaling enabled (default in many configurations).
Generated on May 28, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
3News mentions
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