diff --git a/SOURCES/1756-rtmutex-use-waiter-task-in-remove-waiter.patch b/SOURCES/1756-rtmutex-use-waiter-task-in-remove-waiter.patch new file mode 100644 index 000000000..87ed85eb4 --- /dev/null +++ b/SOURCES/1756-rtmutex-use-waiter-task-in-remove-waiter.patch @@ -0,0 +1,90 @@ +From 3bfdc63936dd4773109b7b8c280c0f3b5ae7d349 Mon Sep 17 00:00:00 2001 +From: Keenan Dong +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 +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 + +[ 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(¤t->pi_lock); +- rt_mutex_dequeue(lock, waiter); +- current->pi_blocked_on = NULL; +- raw_spin_unlock(¤t->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 + diff --git a/SOURCES/1757-rtmutex-skip-remove-waiter-when-not-enqueued.patch b/SOURCES/1757-rtmutex-skip-remove-waiter-when-not-enqueued.patch new file mode 100644 index 000000000..9959b05ad --- /dev/null +++ b/SOURCES/1757-rtmutex-skip-remove-waiter-when-not-enqueued.patch @@ -0,0 +1,77 @@ +From 40a25d59e85b3c8709ac2424d44f65610467871e Mon Sep 17 00:00:00 2001 +From: Davidlohr Bueso +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 +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 + +[ 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 + diff --git a/SPECS/kernel.spec b/SPECS/kernel.spec index 4c5c00661..c127a50f8 100644 --- a/SPECS/kernel.spec +++ b/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 687.23.1 +%define pkgrelease 687.23.2 %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 687.23.1%{?buildid}%{?dist} +%define specrelease 687.23.2%{?buildid}%{?dist} # This defines the kabi tarball version %define kabiversion 5.14.0-687.5.1.el9_8 @@ -1628,6 +1628,8 @@ Patch1752: 1752-eventpoll-drop-dead-bool-return-from-ep-remove-epi.patch Patch1753: 1753-eventpoll-drop-vestigial-epi-dying-flag.patch Patch1754: 1754-eventpoll-fix-integer-overflow-in-ep-loop-check-proc.patch Patch1755: 1755-eventpoll-refresh-epi-fget-ep-remove-file-comments.patch +Patch1756: 1756-rtmutex-use-waiter-task-in-remove-waiter.patch +Patch1757: 1757-rtmutex-skip-remove-waiter-when-not-enqueued.patch # END OF PATCH DEFINITIONS %description @@ -3023,6 +3025,8 @@ ApplyPatch 1752-eventpoll-drop-dead-bool-return-from-ep-remove-epi.patch ApplyPatch 1753-eventpoll-drop-vestigial-epi-dying-flag.patch ApplyPatch 1754-eventpoll-fix-integer-overflow-in-ep-loop-check-proc.patch ApplyPatch 1755-eventpoll-refresh-epi-fget-ep-remove-file-comments.patch +ApplyPatch 1756-rtmutex-use-waiter-task-in-remove-waiter.patch +ApplyPatch 1757-rtmutex-skip-remove-waiter-when-not-enqueued.patch # END OF PATCH APPLICATIONS # Any further pre-build tree manipulations happen here. @@ -5097,6 +5101,10 @@ fi # # %changelog +* Wed Jul 08 2026 Andrew Lukoshko - 5.14.0-687.23.2 +- Bring back the rtmutex self-deadlock NULL pointer dereference fixes in + remove_waiter() ahead of RHEL, upstream 3bfdc63936dd + 40a25d59e85b (1756, 1757) + * Wed Jul 08 2026 Andrew Lukoshko - 5.14.0-687.23.1 - Recreate RHEL 5.14.0-687.23.1 from CentOS Stream and upstream stable backports (1739-1755) - The AlmaLinux ahead-of-RHEL eventpoll CVE-2026-46242 fix (1712) is superseded by