From 7d57f84115b3378b38480bb1285c4572d752b2f9 Mon Sep 17 00:00:00 2001 From: Tashfin Shakeer Rhythm Date: Wed, 29 Jul 2026 02:39:16 +0600 Subject: [PATCH 1/4] tcp: fix an incorrect __user annotation on tcp_proc_delayed_ack_control No user pointers for sysctls anymore. Fixes: c3f877ec98a12 ("BACKPORT: sysctl: pass kernel pointers to ->proc_handler") Change-Id: Ie7d47a3bb5ed4238cea83a493937f38a3fee2571 Signed-off-by: Tashfin Shakeer Rhythm --- include/net/tcp.h | 2 +- net/ipv4/tcp_timer.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index 4d82a2ae305e..ae0a14b6f76f 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -363,7 +363,7 @@ extern int tcp_use_userconfig_sysctl_handler(struct ctl_table *table, int write, void __user *buffer, size_t *length, loff_t *ppos); extern int tcp_proc_delayed_ack_control(struct ctl_table *table, int write, - void __user *buffer, size_t *length, + void *buffer, size_t *length, loff_t *ppos); static inline void tcp_dec_quickack_mode(struct sock *sk) diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index cbd79e175fc7..76f852ea4cb7 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -46,7 +46,7 @@ static void set_tcp_default(void) /*sysctl handler for tcp_ack realted master control */ int tcp_proc_delayed_ack_control(struct ctl_table *table, int write, - void __user *buffer, size_t *length, + void *buffer, size_t *length, loff_t *ppos) { int ret = proc_dointvec_minmax(table, write, buffer, length, ppos); From 52d3b2007e9932a4cb356a0e126629ca8ec87850 Mon Sep 17 00:00:00 2001 From: Tashfin Shakeer Rhythm Date: Wed, 29 Jul 2026 02:41:58 +0600 Subject: [PATCH 2/4] tcp: fix an incorrect __user annotation on tcp_use_userconfig_sysctl_handler No user pointers for sysctls anymore. Fixes: c3f877ec98a12 ("BACKPORT: sysctl: pass kernel pointers to ->proc_handler") Change-Id: Ia9c27a7308aad6fb9b6476f1000d2588d0367014 Signed-off-by: Tashfin Shakeer Rhythm --- include/net/tcp.h | 2 +- net/ipv4/tcp_timer.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index ae0a14b6f76f..daf0a142f36c 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -360,7 +360,7 @@ ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos, /* sysctl master controller */ extern int tcp_use_userconfig_sysctl_handler(struct ctl_table *table, - int write, void __user *buffer, size_t *length, + int write, void *buffer, size_t *length, loff_t *ppos); extern int tcp_proc_delayed_ack_control(struct ctl_table *table, int write, void *buffer, size_t *length, diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 76f852ea4cb7..5fb3b234a19e 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -60,7 +60,7 @@ int tcp_proc_delayed_ack_control(struct ctl_table *table, int write, /*sysctl handler for tcp_ack realted master control */ int tcp_use_userconfig_sysctl_handler(struct ctl_table *table, int write, - void __user *buffer, size_t *length, + void *buffer, size_t *length, loff_t *ppos) { int ret = proc_dointvec_minmax(table, write, buffer, length, ppos); From 46787e4e665e8ddd5ab30f162ba3ad96a7ea5c78 Mon Sep 17 00:00:00 2001 From: Keenan Dong Date: Wed, 8 Apr 2026 16:46:00 +0800 Subject: [PATCH 3/4] BACKPORT: rtmutex: Use waiter::task instead of current in remove_waiter() remove_waiter() is used by the slowlock paths, but it is also used for proxy-lock rollback in rt_mutex_start_proxy_lock() when invoked from futex_requeue(). In the latter case waiter::task is not current, but remove_waiter() operates on current for the dequeue operation. That results in several problems: 1) the rbtree dequeue happens without waiter::task::pi_lock being held 2) the waiter task's pi_blocked_on state is not cleared, which leaves a dangling pointer primed for UAF around. 3) rt_mutex_adjust_prio_chain() operates on the wrong top priority waiter task Use waiter::task instead of current in all related operations in remove_waiter() to cure those problems. [ tglx: Fixup rt_mutex_adjust_prio_chain(), add a comment and amend the changelog ] Fixes: 8161239a8bcc ("rtmutex: Simplify PI algorithm and make highest prio task get lock") Change-Id: I3ff8da2830773e04f55828b11c9d461ab6ee57c5 Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Signed-off-by: Keenan Dong Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org [Tashar02: Open-code scoped_guard() on msm-5.4] Signed-off-by: Tashfin Shakeer Rhythm --- kernel/locking/rtmutex.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 3dde5da4b778..8b096ae3a8a2 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1062,20 +1062,23 @@ static void mark_wakeup_next_waiter(struct wake_q_head *wake_q, * * Must be called with lock->wait_lock held and interrupts disabled. I must * have just failed to try_to_take_rt_mutex(). + * + * When invoked from rt_mutex_start_proxy_lock() waiter::task != current ! */ static void remove_waiter(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) { bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock)); struct task_struct *owner = rt_mutex_owner(lock); + struct task_struct *waiter_task = waiter->task; struct rt_mutex *next_lock; lockdep_assert_held(&lock->wait_lock); - raw_spin_lock(¤t->pi_lock); + raw_spin_lock(&waiter_task->pi_lock); rt_mutex_dequeue(lock, waiter); - current->pi_blocked_on = NULL; - raw_spin_unlock(¤t->pi_lock); + waiter_task->pi_blocked_on = NULL; + raw_spin_unlock(&waiter_task->pi_lock); /* * Only update priority if the waiter was the highest priority @@ -1111,7 +1114,7 @@ static void remove_waiter(struct rt_mutex *lock, raw_spin_unlock_irq(&lock->wait_lock); rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock, - next_lock, NULL, current); + next_lock, NULL, waiter_task); raw_spin_lock_irq(&lock->wait_lock); } From 78340378432c847603c90473b1c3bae5c28bac9e Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Thu, 7 May 2026 04:29:13 -0700 Subject: [PATCH 4/4] BACKPORT: locking/rtmutex: Skip remove_waiter() when waiter is not enqueued syzbot triggered the following splat in remove_waiter() via FUTEX_CMP_REQUEUE_PI: KASAN: null-ptr-deref in range [0x0000000000000a88-0x0000000000000a8f] class_raw_spinlock_constructor remove_waiter+0x159/0x1200 kernel/locking/rtmutex.c:1561 rt_mutex_start_proxy_lock+0x103/0x120 futex_requeue+0x10e4/0x20d0 __x64_sys_futex+0x34f/0x4d0 task_blocks_on_rt_mutex() does not arm the waiter upon deadlock detection, leaving waiter->task nil, where 3bfdc63936dd ("rtmutex: Use waiter::task instead of current in remove_waiter()") made this fatal. Furthermore, rt_mutex_start_proxy_lock() should not be calling into remove_waiter() upon a successfully grabbing the rtmutex. 1a1fb985f2e2 ("futex: Handle early deadlock return correctly"), moved the remove_waiter() out of __rt_mutex_start_proxy_lock() (where 'ret' was only ever 0 or < 0) into the wrapper. Tighten this check to account for try_to_take_rt_mutex(). Fixes: 3bfdc63936dd ("rtmutex: Use waiter::task instead of current in remove_waiter()") Change-Id: Ib19a2f223ba67d20496c0ae95096747f5350c520 Reported-by: syzbot+78147abe6c524f183ee9@syzkaller.appspotmail.com Signed-off-by: Davidlohr Bueso Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Closes: https://lore.kernel.org/all/69f114ac.050a0220.ac8b.0003.GAE@google.com/ Link: https://patch.msgid.link/20260507112913.1019537-1-dave@stgolabs.net Signed-off-by: Tashfin Shakeer Rhythm --- kernel/locking/rtmutex.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 8b096ae3a8a2..01cb685c677c 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1075,6 +1075,9 @@ static void remove_waiter(struct rt_mutex *lock, lockdep_assert_held(&lock->wait_lock); + if (!waiter_task) /* never enqueued */ + return; + raw_spin_lock(&waiter_task->pi_lock); rt_mutex_dequeue(lock, waiter); waiter_task->pi_blocked_on = NULL; @@ -1804,7 +1807,7 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock, raw_spin_lock_irq(&lock->wait_lock); ret = __rt_mutex_start_proxy_lock(lock, waiter, task); - if (unlikely(ret)) + if (unlikely(ret < 0)) remove_waiter(lock, waiter); raw_spin_unlock_irq(&lock->wait_lock);