* FAILED: patch "[PATCH] exec: Cleanup POSIX timers right after de_thread()" failed to apply to 6.1-stable tree
@ 2026-09-22 8:26 gregkh
2026-09-22 15:22 ` [PATCH 6.1.y] exec: Cleanup POSIX timers right after de_thread() Sasha Levin
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: gregkh @ 2026-09-22 8:26 UTC (permalink / raw)
To: imv4bel, frederic, oleg, red993688, tglx; +Cc: stable
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 acb03d3881818581052924a9bbbe92b8741ed448
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026092225-humongous-ultimate-9930@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From acb03d3881818581052924a9bbbe92b8741ed448 Mon Sep 17 00:00:00 2001
From: Hyunwoo Kim <imv4bel@gmail.com>
Date: Fri, 11 Sep 2026 11:09:17 +0200
Subject: [PATCH] exec: Cleanup POSIX timers right after de_thread()
A per-thread CPU timer holds a reference to the PID of the thread it is
attached to and, while it is armed, its node is queued in that thread's
posix_cputimers. The task is looked up by that PID.
When a non-leader thread exec()s, de_thread() changes which task owns
that PID. pid_task(timer->it.cpu.pid, PIDTYPE_PID) then returns NULL,
but the node is still queued on tsk, which is alive. timer_lock_sighand()
takes a failed lookup to mean that the node is already dequeued, so it
has nothing to undo.
begin_new_exec() calls posix_cpu_timers_exit(me) right after
exec_task_namespaces() and that removes the leftover node, so the state
normally stays invisible. But bprm->point_of_no_return is set before
de_thread(), so if unshare_files(), set_mm_exe_file(), exec_mmap() or
exec_task_namespaces() fails, the task dies before it gets there.
exit_itimers() then frees the k_itimer while its node is still queued,
and reaping tsk later erases that freed node from the rbtree.
In short:
the non-leader thread B the parent
timer_create(CLOCK_THREAD_CPUTIME_ID)
timer_settime()
arm_timer() // the node is queued on B
execve()
de_thread(B)
exchange_tids(B, leader) // B's PID now belongs to the leader
release_task(leader)
__exit_signal(leader)
posix_cpu_timers_exit(leader) // cleans leader's queue, not B's
__unhash_process(leader) // that PID has no task anymore
exec_mmap()
mmap_read_lock_killable(old_mm)
kill(B, SIGKILL)
// -EINTR
get_signal()
do_exit()
exit_itimers()
posix_timer_delete()
posix_cpu_timer_del()
posix_timer_unhash_and_free() // freed while still queued
wait4()
release_task(B)
posix_cpu_timers_exit(B)
cleanup_timerqueue()
timerqueue_del() // use-after-free
Move the POSIX timer cleanup right after de_thread() before any of the
later failure conditions brings the task into do_exit().
[ tglx: Move the cleanup right after de_thread() ]
Fixes: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Kijo Park <red993688@gmail.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/ao7Q8miiuLAPVnWv@v4bel
Link: https://patch.msgid.link/20260911090541.627712075@kernel.org
diff --git a/fs/exec.c b/fs/exec.c
index d3081c8f7c10..819643408e6d 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1115,6 +1115,17 @@ static struct file *bprm_identity_file(const struct linux_binprm *bprm)
return bprm->file;
}
+static void posixtimer_exec(struct task_struct *me)
+{
+#ifdef CONFIG_POSIX_TIMERS
+ spin_lock_irq(&me->sighand->siglock);
+ posix_cpu_timers_exit(me);
+ spin_unlock_irq(&me->sighand->siglock);
+ exit_itimers(me);
+ flush_itimer_signals();
+#endif
+}
+
/*
* Calling this is the point of no return. None of the failures will be
* seen by userspace since either the process is already taking a fatal
@@ -1152,6 +1163,16 @@ int begin_new_exec(struct linux_binprm * bprm)
retval = de_thread(me);
if (retval)
goto out;
+
+ /*
+ * This must be done here to ensure that POSIX CPU timers which were
+ * armed on the current task are dequeued from me::posix_cputimers.
+ * Otherwise in case of a TID switch the deletion of the related POSIX
+ * timer would not remove an enqueued timer because the TID lookup
+ * of the old TID fails.
+ */
+ posixtimer_exec(me);
+
/* see the comment in check_unsafe_exec() */
current->fs->in_exec = 0;
/*
@@ -1206,14 +1227,6 @@ int begin_new_exec(struct linux_binprm * bprm)
if (retval)
goto out_unlock;
-#ifdef CONFIG_POSIX_TIMERS
- spin_lock_irq(&me->sighand->siglock);
- posix_cpu_timers_exit(me);
- spin_unlock_irq(&me->sighand->siglock);
- exit_itimers(me);
- flush_itimer_signals();
-#endif
-
/*
* Make the signal table private.
*/
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 6.1.y] exec: Cleanup POSIX timers right after de_thread()
2026-09-22 8:26 FAILED: patch "[PATCH] exec: Cleanup POSIX timers right after de_thread()" failed to apply to 6.1-stable tree gregkh
@ 2026-09-22 15:22 ` Sasha Levin
2026-10-28 12:21 ` [STABLE v5.15] " Lee Jones
2026-10-28 12:21 ` [STABLE v5.10] " Lee Jones
2 siblings, 0 replies; 6+ messages in thread
From: Sasha Levin @ 2026-09-22 15:22 UTC (permalink / raw)
To: stable
Cc: Hyunwoo Kim, Thomas Gleixner, Kijo Park, Oleg Nesterov,
Frederic Weisbecker, Sasha Levin
From: Hyunwoo Kim <imv4bel@gmail.com>
[ Upstream commit acb03d3881818581052924a9bbbe92b8741ed448 ]
A per-thread CPU timer holds a reference to the PID of the thread it is
attached to and, while it is armed, its node is queued in that thread's
posix_cputimers. The task is looked up by that PID.
When a non-leader thread exec()s, de_thread() changes which task owns
that PID. pid_task(timer->it.cpu.pid, PIDTYPE_PID) then returns NULL,
but the node is still queued on tsk, which is alive. timer_lock_sighand()
takes a failed lookup to mean that the node is already dequeued, so it
has nothing to undo.
begin_new_exec() calls posix_cpu_timers_exit(me) right after
exec_task_namespaces() and that removes the leftover node, so the state
normally stays invisible. But bprm->point_of_no_return is set before
de_thread(), so if unshare_files(), set_mm_exe_file(), exec_mmap() or
exec_task_namespaces() fails, the task dies before it gets there.
exit_itimers() then frees the k_itimer while its node is still queued,
and reaping tsk later erases that freed node from the rbtree.
In short:
the non-leader thread B the parent
timer_create(CLOCK_THREAD_CPUTIME_ID)
timer_settime()
arm_timer() // the node is queued on B
execve()
de_thread(B)
exchange_tids(B, leader) // B's PID now belongs to the leader
release_task(leader)
__exit_signal(leader)
posix_cpu_timers_exit(leader) // cleans leader's queue, not B's
__unhash_process(leader) // that PID has no task anymore
exec_mmap()
mmap_read_lock_killable(old_mm)
kill(B, SIGKILL)
// -EINTR
get_signal()
do_exit()
exit_itimers()
posix_timer_delete()
posix_cpu_timer_del()
posix_timer_unhash_and_free() // freed while still queued
wait4()
release_task(B)
posix_cpu_timers_exit(B)
cleanup_timerqueue()
timerqueue_del() // use-after-free
Move the POSIX timer cleanup right after de_thread() before any of the
later failure conditions brings the task into do_exit().
[ tglx: Move the cleanup right after de_thread() ]
Fixes: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Kijo Park <red993688@gmail.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/ao7Q8miiuLAPVnWv@v4bel
Link: https://patch.msgid.link/20260911090541.627712075@kernel.org
[ kept timer cleanup inline instead of introducing upstream’s posixtimer_exec() helper. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/exec.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index e4dd402aa4ce6..8e91240a71e17 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1268,6 +1268,21 @@ int begin_new_exec(struct linux_binprm * bprm)
if (retval)
goto out;
+ /*
+ * This must be done here to ensure that POSIX CPU timers which were
+ * armed on the current task are dequeued from me::posix_cputimers.
+ * Otherwise in case of a TID switch the deletion of the related POSIX
+ * timer would not remove an enqueued timer because the TID lookup
+ * of the old TID fails.
+ */
+#ifdef CONFIG_POSIX_TIMERS
+ spin_lock_irq(&me->sighand->siglock);
+ posix_cpu_timers_exit(me);
+ spin_unlock_irq(&me->sighand->siglock);
+ exit_itimers(me);
+ flush_itimer_signals();
+#endif
+
/*
* Cancel any io_uring activity across execve
*/
@@ -1302,14 +1317,6 @@ int begin_new_exec(struct linux_binprm * bprm)
bprm->mm = NULL;
-#ifdef CONFIG_POSIX_TIMERS
- spin_lock_irq(&me->sighand->siglock);
- posix_cpu_timers_exit(me);
- spin_unlock_irq(&me->sighand->siglock);
- exit_itimers(me);
- flush_itimer_signals();
-#endif
-
/*
* Make the signal table private.
*/
--
2.53.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [STABLE v5.15] exec: Cleanup POSIX timers right after de_thread()
2026-09-22 8:26 FAILED: patch "[PATCH] exec: Cleanup POSIX timers right after de_thread()" failed to apply to 6.1-stable tree gregkh
2026-09-22 15:22 ` [PATCH 6.1.y] exec: Cleanup POSIX timers right after de_thread() Sasha Levin
@ 2026-10-28 12:21 ` Lee Jones
2026-10-29 18:43 ` Sasha Levin
2026-10-28 12:21 ` [STABLE v5.10] " Lee Jones
2 siblings, 1 reply; 6+ messages in thread
From: Lee Jones @ 2026-10-28 12:21 UTC (permalink / raw)
To: lee
Cc: stable, gregkh, sashal, Hyunwoo Kim, Thomas Gleixner, Kijo Park,
Oleg Nesterov, Frederic Weisbecker
From: Hyunwoo Kim <imv4bel@gmail.com>
commit acb03d3881818581052924a9bbbe92b8741ed448 upstream.
A per-thread CPU timer holds a reference to the PID of the thread it is
attached to and, while it is armed, its node is queued in that thread's
posix_cputimers. The task is looked up by that PID.
When a non-leader thread exec()s, de_thread() changes which task owns
that PID. pid_task(timer->it.cpu.pid, PIDTYPE_PID) then returns NULL,
but the node is still queued on tsk, which is alive. timer_lock_sighand()
takes a failed lookup to mean that the node is already dequeued, so it
has nothing to undo.
begin_new_exec() calls posix_cpu_timers_exit(me) right after
exec_task_namespaces() and that removes the leftover node, so the state
normally stays invisible. But bprm->point_of_no_return is set before
de_thread(), so if unshare_files(), set_mm_exe_file(), exec_mmap() or
exec_task_namespaces() fails, the task dies before it gets there.
exit_itimers() then frees the k_itimer while its node is still queued,
and reaping tsk later erases that freed node from the rbtree.
In short:
the non-leader thread B the parent
timer_create(CLOCK_THREAD_CPUTIME_ID)
timer_settime()
arm_timer() // the node is queued on B
execve()
de_thread(B)
exchange_tids(B, leader) // B's PID now belongs to the leader
release_task(leader)
__exit_signal(leader)
posix_cpu_timers_exit(leader) // cleans leader's queue, not B's
__unhash_process(leader) // that PID has no task anymore
exec_mmap()
mmap_read_lock_killable(old_mm)
kill(B, SIGKILL)
// -EINTR
get_signal()
do_exit()
exit_itimers()
posix_timer_delete()
posix_cpu_timer_del()
posix_timer_unhash_and_free() // freed while still queued
wait4()
release_task(B)
posix_cpu_timers_exit(B)
cleanup_timerqueue()
timerqueue_del() // use-after-free
Move the POSIX timer cleanup right after de_thread() before any of the
later failure conditions brings the task into do_exit().
[ tglx: Move the cleanup right after de_thread() ]
Fixes: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Kijo Park <red993688@gmail.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/ao7Q8miiuLAPVnWv@v4bel
Link: https://patch.msgid.link/20260911090541.627712075@kernel.org
[Lee: Context conflict only - no functional change]
Signed-off-by: Lee Jones <lee@kernel.org>
---
fs/exec.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 6797c8cf88f4..5efe7ae6f968 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1234,6 +1234,17 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
perf_event_comm(tsk, exec);
}
+static void posixtimer_exec(struct task_struct *me)
+{
+#ifdef CONFIG_POSIX_TIMERS
+ spin_lock_irq(&me->sighand->siglock);
+ posix_cpu_timers_exit(me);
+ spin_unlock_irq(&me->sighand->siglock);
+ exit_itimers(me);
+ flush_itimer_signals();
+#endif
+}
+
/*
* Calling this is the point of no return. None of the failures will be
* seen by userspace since either the process is already taking a fatal
@@ -1262,6 +1273,15 @@ int begin_new_exec(struct linux_binprm * bprm)
if (retval)
goto out;
+ /*
+ * This must be done here to ensure that POSIX CPU timers which were
+ * armed on the current task are dequeued from me::posix_cputimers.
+ * Otherwise in case of a TID switch the deletion of the related POSIX
+ * timer would not remove an enqueued timer because the TID lookup
+ * of the old TID fails.
+ */
+ posixtimer_exec(me);
+
/*
* Cancel any io_uring activity across execve
*/
@@ -1310,14 +1330,6 @@ int begin_new_exec(struct linux_binprm * bprm)
bprm->mm = NULL;
-#ifdef CONFIG_POSIX_TIMERS
- spin_lock_irq(&me->sighand->siglock);
- posix_cpu_timers_exit(me);
- spin_unlock_irq(&me->sighand->siglock);
- exit_itimers(me);
- flush_itimer_signals();
-#endif
-
/*
* Make the signal table private.
*/
--
2.56.0.313.g2479322e68-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [STABLE v5.10] exec: Cleanup POSIX timers right after de_thread()
2026-09-22 8:26 FAILED: patch "[PATCH] exec: Cleanup POSIX timers right after de_thread()" failed to apply to 6.1-stable tree gregkh
2026-09-22 15:22 ` [PATCH 6.1.y] exec: Cleanup POSIX timers right after de_thread() Sasha Levin
2026-10-28 12:21 ` [STABLE v5.15] " Lee Jones
@ 2026-10-28 12:21 ` Lee Jones
2026-10-29 18:43 ` Sasha Levin
2 siblings, 1 reply; 6+ messages in thread
From: Lee Jones @ 2026-10-28 12:21 UTC (permalink / raw)
To: lee
Cc: stable, gregkh, sashal, Hyunwoo Kim, Thomas Gleixner, Kijo Park,
Oleg Nesterov, Frederic Weisbecker
From: Hyunwoo Kim <imv4bel@gmail.com>
commit acb03d3881818581052924a9bbbe92b8741ed448 upstream.
A per-thread CPU timer holds a reference to the PID of the thread it is
attached to and, while it is armed, its node is queued in that thread's
posix_cputimers. The task is looked up by that PID.
When a non-leader thread exec()s, de_thread() changes which task owns
that PID. pid_task(timer->it.cpu.pid, PIDTYPE_PID) then returns NULL,
but the node is still queued on tsk, which is alive. timer_lock_sighand()
takes a failed lookup to mean that the node is already dequeued, so it
has nothing to undo.
begin_new_exec() calls posix_cpu_timers_exit(me) right after
exec_task_namespaces() and that removes the leftover node, so the state
normally stays invisible. But bprm->point_of_no_return is set before
de_thread(), so if unshare_files(), set_mm_exe_file(), exec_mmap() or
exec_task_namespaces() fails, the task dies before it gets there.
exit_itimers() then frees the k_itimer while its node is still queued,
and reaping tsk later erases that freed node from the rbtree.
In short:
the non-leader thread B the parent
timer_create(CLOCK_THREAD_CPUTIME_ID)
timer_settime()
arm_timer() // the node is queued on B
execve()
de_thread(B)
exchange_tids(B, leader) // B's PID now belongs to the leader
release_task(leader)
__exit_signal(leader)
posix_cpu_timers_exit(leader) // cleans leader's queue, not B's
__unhash_process(leader) // that PID has no task anymore
exec_mmap()
mmap_read_lock_killable(old_mm)
kill(B, SIGKILL)
// -EINTR
get_signal()
do_exit()
exit_itimers()
posix_timer_delete()
posix_cpu_timer_del()
posix_timer_unhash_and_free() // freed while still queued
wait4()
release_task(B)
posix_cpu_timers_exit(B)
cleanup_timerqueue()
timerqueue_del() // use-after-free
Move the POSIX timer cleanup right after de_thread() before any of the
later failure conditions brings the task into do_exit().
[ tglx: Move the cleanup right after de_thread() ]
Fixes: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Kijo Park <red993688@gmail.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/ao7Q8miiuLAPVnWv@v4bel
Link: https://patch.msgid.link/20260911090541.627712075@kernel.org
[Lee: Context conflict only - no functional change]
Signed-off-by: Lee Jones <lee@kernel.org>
---
fs/exec.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index a2f72a503b7a..5980f577026d 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1234,6 +1234,17 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
perf_event_comm(tsk, exec);
}
+static void posixtimer_exec(struct task_struct *me)
+{
+#ifdef CONFIG_POSIX_TIMERS
+ spin_lock_irq(&me->sighand->siglock);
+ posix_cpu_timers_exit(me);
+ spin_unlock_irq(&me->sighand->siglock);
+ exit_itimers(me);
+ flush_itimer_signals();
+#endif
+}
+
/*
* Calling this is the point of no return. None of the failures will be
* seen by userspace since either the process is already taking a fatal
@@ -1262,6 +1273,15 @@ int begin_new_exec(struct linux_binprm * bprm)
if (retval)
goto out;
+ /*
+ * This must be done here to ensure that POSIX CPU timers which were
+ * armed on the current task are dequeued from me::posix_cputimers.
+ * Otherwise in case of a TID switch the deletion of the related POSIX
+ * timer would not remove an enqueued timer because the TID lookup
+ * of the old TID fails.
+ */
+ posixtimer_exec(me);
+
/* Ensure the files table is not shared. */
retval = unshare_files();
if (retval)
@@ -1303,14 +1323,6 @@ int begin_new_exec(struct linux_binprm * bprm)
bprm->mm = NULL;
-#ifdef CONFIG_POSIX_TIMERS
- spin_lock_irq(&me->sighand->siglock);
- posix_cpu_timers_exit(me);
- spin_unlock_irq(&me->sighand->siglock);
- exit_itimers(me);
- flush_itimer_signals();
-#endif
-
/*
* Make the signal table private.
*/
--
2.56.0.313.g2479322e68-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [STABLE v5.15] exec: Cleanup POSIX timers right after de_thread()
2026-10-28 12:21 ` [STABLE v5.15] " Lee Jones
@ 2026-10-29 18:43 ` Sasha Levin
0 siblings, 0 replies; 6+ messages in thread
From: Sasha Levin @ 2026-10-29 18:43 UTC (permalink / raw)
To: lee
Cc: Sasha Levin, stable, gregkh, Hyunwoo Kim, Thomas Gleixner,
Kijo Park, Oleg Nesterov, Frederic Weisbecker
> commit acb03d3881818581052924a9bbbe92b8741ed448 upstream.
Queued for 5.15, thanks.
--
Thanks,
Sasha
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [STABLE v5.10] exec: Cleanup POSIX timers right after de_thread()
2026-10-28 12:21 ` [STABLE v5.10] " Lee Jones
@ 2026-10-29 18:43 ` Sasha Levin
0 siblings, 0 replies; 6+ messages in thread
From: Sasha Levin @ 2026-10-29 18:43 UTC (permalink / raw)
To: lee
Cc: Sasha Levin, stable, gregkh, Hyunwoo Kim, Thomas Gleixner,
Kijo Park, Oleg Nesterov, Frederic Weisbecker
> commit acb03d3881818581052924a9bbbe92b8741ed448 upstream.
Queued for 5.10, thanks.
--
Thanks,
Sasha
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-10-29 18:43 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2026-09-22 8:26 FAILED: patch "[PATCH] exec: Cleanup POSIX timers right after de_thread()" failed to apply to 6.1-stable tree gregkh
2026-09-22 15:22 ` [PATCH 6.1.y] exec: Cleanup POSIX timers right after de_thread() Sasha Levin
2026-10-28 12:21 ` [STABLE v5.15] " Lee Jones
2026-10-29 18:43 ` Sasha Levin
2026-10-28 12:21 ` [STABLE v5.10] " Lee Jones
2026-10-29 18:43 ` Sasha Levin
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