Fix rtmutex/futex self-deadlock NULL deref in remove_waiter() ahead of RHEL; bump to 687.22.2

SOURCES/1736-rtmutex-use-waiter-task-in-remove-waiter.patch

@@ -0,0 +1,90 @@
+From 3bfdc63936dd4773109b7b8c280c0f3b5ae7d349 Mon Sep 17 00:00:00 2001
+From: Keenan Dong <keenanat2000@gmail.com>
+Date: Wed, 8 Apr 2026 16:46:00 +0800
+Subject: [PATCH] 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")
+Reported-by: Yuan Tan <yuantan098@gmail.com>
+Reported-by: Yifan Wu <yifanwucs@gmail.com>
+Reported-by: Juefei Pu <tomapufckgml@gmail.com>
+Reported-by: Xin Liu <bird@lzu.edu.cn>
+Signed-off-by: Keenan Dong <keenanat2000@gmail.com>
+Signed-off-by: Thomas Gleixner <tglx@kernel.org>
+Cc: stable@vger.kernel.org
+
+[ AlmaLinux: adapted to a9 (5.14.0-687.5.1.el9_8). No functional change vs
+  upstream commit 3bfdc63936dd; only diff hunk offsets differ. The
+  scoped_guard(raw_spinlock, ...) form is used verbatim: it is available in
+  this tree via include/linux/cleanup.h and DEFINE_LOCK_GUARD_1(raw_spinlock,
+  ...) in include/linux/spinlock.h. ]
+---
+ kernel/locking/rtmutex.c | 13 ++++++++-----
+ 1 file changed, 8 insertions(+), 5 deletions(-)
+
+diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
+index 1eb4f9499..e881d9548 100644
+--- a/kernel/locking/rtmutex.c
++++ b/kernel/locking/rtmutex.c
+@@ -1534,20 +1534,23 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
+  *
+  * Must be called with lock->wait_lock held and interrupts disabled. It must
+  * have just failed to try_to_take_rt_mutex().
++ *
++ * When invoked from rt_mutex_start_proxy_lock() waiter::task != current !
+  */
+ static void __sched remove_waiter(struct rt_mutex_base *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_base *next_lock;
+ 
+ 	lockdep_assert_held(&lock->wait_lock);
+ 
+-	raw_spin_lock(&current->pi_lock);
+-	rt_mutex_dequeue(lock, waiter);
+-	current->pi_blocked_on = NULL;
+-	raw_spin_unlock(&current->pi_lock);
++	scoped_guard(raw_spinlock, &waiter_task->pi_lock) {
++		rt_mutex_dequeue(lock, waiter);
++		waiter_task->pi_blocked_on = NULL;
++	}
+ 
+ 	/*
+ 	 * Only update priority if the waiter was the highest priority
+@@ -1583,7 +1586,7 @@ static void __sched remove_waiter(struct rt_mutex_base *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);
+ }
+-- 
+2.43.7
+

SOURCES/1738-rtmutex-skip-remove-waiter-when-not-enqueued.patch

@@ -0,0 +1,77 @@
+From 40a25d59e85b3c8709ac2424d44f65610467871e Mon Sep 17 00:00:00 2001
+From: Davidlohr Bueso <dave@stgolabs.net>
+Date: Thu, 7 May 2026 04:29:13 -0700
+Subject: [PATCH] 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()")
+Reported-by: syzbot+78147abe6c524f183ee9@syzkaller.appspotmail.com
+Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
+Signed-off-by: Thomas Gleixner <tglx@kernel.org>
+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
+
+[ AlmaLinux: adapted to a9 (5.14.0-687.5.1.el9_8). No change vs upstream
+  commit 40a25d59e85b. Both hunks apply cleanly: kernel/locking/rtmutex.c
+  remove_waiter() (the waiter_task local comes from the earlier
+  "rtmutex: Use waiter::task ..." patch) and kernel/locking/rtmutex_api.c
+  rt_mutex_start_proxy_lock(). The "ret < 0" tightening is meaningful in this
+  tree: __rt_mutex_start_proxy_lock() returns 1 on try_to_take_rt_mutex()
+  success, so the prior "if (unlikely(ret))" wrongly invoked remove_waiter()
+  after acquiring the lock. ]
+---
+ kernel/locking/rtmutex.c     | 3 +++
+ kernel/locking/rtmutex_api.c | 2 +-
+ 2 files changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
+index e881d9548..1cecc1092 100644
+--- a/kernel/locking/rtmutex.c
++++ b/kernel/locking/rtmutex.c
+@@ -1547,6 +1547,9 @@ static void __sched remove_waiter(struct rt_mutex_base *lock,
+ 
+ 	lockdep_assert_held(&lock->wait_lock);
+ 
++	if (!waiter_task) /* never enqueued */
++		return;
++
+ 	scoped_guard(raw_spinlock, &waiter_task->pi_lock) {
+ 		rt_mutex_dequeue(lock, waiter);
+ 		waiter_task->pi_blocked_on = NULL;
+diff --git a/kernel/locking/rtmutex_api.c b/kernel/locking/rtmutex_api.c
+index 6614ccdc1..341a540f6 100644
+--- a/kernel/locking/rtmutex_api.c
++++ b/kernel/locking/rtmutex_api.c
+@@ -347,7 +347,7 @@ int __sched rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
+ 
+ 	raw_spin_lock_irq(&lock->wait_lock);
+ 	ret = __rt_mutex_start_proxy_lock(lock, waiter, task, &wake_q);
+-	if (unlikely(ret))
++	if (unlikely(ret < 0))
+ 		remove_waiter(lock, waiter);
+ 	preempt_disable();
+ 	raw_spin_unlock_irq(&lock->wait_lock);
+-- 
+2.43.7
+

SPECS/kernel.spec

@@ -176,13 +176,13 @@ Summary: The Linux kernel
 # define buildid .local
 %define specversion 5.14.0
 %define patchversion 5.14
-%define pkgrelease 687.22.1
+%define pkgrelease 687.22.2
 %define kversion 5
 %define tarfile_release 5.14.0-687.5.1.el9_8
 # This is needed to do merge window version magic
 %define patchlevel 14
 # This allows pkg_release to have configurable %%{?dist} tag
-%define specrelease 687.22.1%{?buildid}%{?dist}
+%define specrelease 687.22.2%{?buildid}%{?dist}
 # This defines the kabi tarball version
 %define kabiversion 5.14.0-687.5.1.el9_8
 
@@ -1612,6 +1612,8 @@ Patch1732: 1732-net-gro-don-t-merge-zcopy-skbs.patch
 Patch1733: 1733-xfrm-defensively-unhash-xfrm-state-lists-in-xfrm-state-delet.patch
 Patch1734: 1734-smb-client-fix-off-by-8-bounds-check-in-check-wsl-eas.patch
 Patch1735: 1735-smb-client-fix-out-of-bounds-read-in-smb2-compound-op.patch
+Patch1736: 1736-rtmutex-use-waiter-task-in-remove-waiter.patch
+Patch1738: 1738-rtmutex-skip-remove-waiter-when-not-enqueued.patch
 # END OF PATCH DEFINITIONS
 
 %description
@@ -2991,6 +2993,8 @@ ApplyPatch 1732-net-gro-don-t-merge-zcopy-skbs.patch
 ApplyPatch 1733-xfrm-defensively-unhash-xfrm-state-lists-in-xfrm-state-delet.patch
 ApplyPatch 1734-smb-client-fix-off-by-8-bounds-check-in-check-wsl-eas.patch
 ApplyPatch 1735-smb-client-fix-out-of-bounds-read-in-smb2-compound-op.patch
+ApplyPatch 1736-rtmutex-use-waiter-task-in-remove-waiter.patch
+ApplyPatch 1738-rtmutex-skip-remove-waiter-when-not-enqueued.patch
 # END OF PATCH APPLICATIONS
 
 # Any further pre-build tree manipulations happen here.
@@ -5065,6 +5069,12 @@ fi
 #
 #
 %changelog
+* Tue Jul 08 2026 Andrew Lukoshko <alukoshko@almalinux.org> - 5.14.0-687.22.2
+- Fix rtmutex self-deadlock NULL pointer dereference in remove_waiter() ahead of
+  RHEL, upstream 3bfdc63936dd + 40a25d59e85b (1736, 1738); the futex_requeue guard
+  74e144274af3 was dropped, reverted upstream by 39def6d250d3 (the NULL deref is
+  fully handled by 40a25d59e85b)
+
 * Mon Jul 07 2026 Andrew Lukoshko <alukoshko@almalinux.org> - 5.14.0-687.22.1
 - Recreate RHEL 5.14.0-687.22.1 from CentOS Stream 9 and upstream stable backports (1713-1735)
 - Retain AlmaLinux ahead-of-RHEL fixes: KVM x86 shadow paging (1710-1711), eventpoll