FAILED: patch "[PATCH] kernel: rerun task_work while freezing in get_signal()" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] kernel: rerun task_work while freezing in get_signal()" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 943ad0b62e3c21f324c4884caa6cb4a871bca05c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024072940-parish-shirt-3e49@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

943ad0b62e3c ("kernel: rerun task_work while freezing in get_signal()")
f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
9963e444f71e ("sched: Widen TAKS_state literals")
f9fc8cad9728 ("sched: Add TASK_ANY for wait_task_inactive()")
9204a97f7ae8 ("sched: Change wait_task_inactive()s match_state")
1fbcaa923ce2 ("freezer,umh: Clean up freezer/initrd interaction")
5950e5d574c6 ("freezer: Have {,un}lock_system_sleep() save/restore flags")
0b9d46fc5ef7 ("sched: Rename task_running() to task_on_cpu()")
8386c414e27c ("PM: hibernate: defer device probing when resuming from hibernation")
57b6de08b5f6 ("ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs")
7b0fe1367ef2 ("ptrace: Document that wait_task_inactive can't fail")
1930a6e739c4 ("Merge tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 943ad0b62e3c21f324c4884caa6cb4a871bca05c Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Wed, 10 Jul 2024 18:58:18 +0100
Subject: [PATCH] kernel: rerun task_work while freezing in get_signal()

io_uring can asynchronously add a task_work while the task is getting
freezed. TIF_NOTIFY_SIGNAL will prevent the task from sleeping in
do_freezer_trap(), and since the get_signal()'s relock loop doesn't
retry task_work, the task will spin there not being able to sleep
until the freezing is cancelled / the task is killed / etc.

Run task_works in the freezer path. Keep the patch small and simple
so it can be easily back ported, but we might need to do some cleaning
after and look if there are other places with similar problems.

Cc: stable@vger.kernel.org
Link: https://github.com/systemd/systemd/issues/33626
Fixes: 12db8b690010c ("entry: Add support for TIF_NOTIFY_SIGNAL")
Reported-by: Julian Orth <ju.orth@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/89ed3a52933370deaaf61a0a620a6ac91f1e754d.1720634146.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/kernel/signal.c b/kernel/signal.c
index 1f9dd41c04be..60c737e423a1 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2600,6 +2600,14 @@ static void do_freezer_trap(void)
 	spin_unlock_irq(&current->sighand->siglock);
 	cgroup_enter_frozen();
 	schedule();
+
+	/*
+	 * We could've been woken by task_work, run it to clear
+	 * TIF_NOTIFY_SIGNAL. The caller will retry if necessary.
+	 */
+	clear_notify_signal();
+	if (unlikely(task_work_pending(current)))
+		task_work_run();
 }
 
 static int ptrace_signal(int signr, kernel_siginfo_t *info, enum pid_type type)

Re: FAILED: patch "[PATCH] kernel: rerun task_work while freezing in get_signal()" failed to apply to 5.15-stable tree

[Jens Axboe]

[-- Attachment #1: Type: text/plain, Size: 981 bytes --]

On 7/29/24 1:49 AM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 5.15-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-5.15.y
> git checkout FETCH_HEAD
> git cherry-pick -x 943ad0b62e3c21f324c4884caa6cb4a871bca05c
> # <resolve conflicts, build, test, etc.>
> git commit -s
> git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024072940-parish-shirt-3e49@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Here's the 5.10-stable and 5.15-stable variant of this. For some
reason this wasn't queued for 5.10 (probably because of the long
ago 5.15-stable backport of io_uring to 5.10), but it should go
there too.

-- 
Jens Axboe


[-- Attachment #2: 0001-kernel-rerun-task_work-while-freezing-in-get_signal.patch --]
[-- Type: text/x-patch, Size: 2630 bytes --]

From f416e4a185dc3d007ea478db3ff75f47cd689eb6 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Wed, 10 Jul 2024 18:58:18 +0100
Subject: [PATCH 1/2] kernel: rerun task_work while freezing in get_signal()

commit 943ad0b62e3c21f324c4884caa6cb4a871bca05c upstream.

io_uring can asynchronously add a task_work while the task is getting
freezed. TIF_NOTIFY_SIGNAL will prevent the task from sleeping in
do_freezer_trap(), and since the get_signal()'s relock loop doesn't
retry task_work, the task will spin there not being able to sleep
until the freezing is cancelled / the task is killed / etc.

Run task_works in the freezer path. Keep the patch small and simple
so it can be easily back ported, but we might need to do some cleaning
after and look if there are other places with similar problems.

Cc: stable@vger.kernel.org
Link: https://github.com/systemd/systemd/issues/33626
Fixes: 12db8b690010c ("entry: Add support for TIF_NOTIFY_SIGNAL")
Reported-by: Julian Orth <ju.orth@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/89ed3a52933370deaaf61a0a620a6ac91f1e754d.1720634146.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 include/linux/sched/signal.h | 6 ++++++
 kernel/signal.c              | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 9743f7d173a0..13c95782c063 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -347,6 +347,12 @@ extern void sigqueue_free(struct sigqueue *);
 extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);
 extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
 
+static inline void clear_notify_signal(void)
+{
+	clear_thread_flag(TIF_NOTIFY_SIGNAL);
+	smp_mb__after_atomic();
+}
+
 static inline int restart_syscall(void)
 {
 	set_tsk_thread_flag(current, TIF_SIGPENDING);
diff --git a/kernel/signal.c b/kernel/signal.c
index c7dbb19219b9..08bccdbb1b46 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2579,6 +2579,14 @@ static void do_freezer_trap(void)
 	spin_unlock_irq(&current->sighand->siglock);
 	cgroup_enter_frozen();
 	freezable_schedule();
+
+	/*
+	 * We could've been woken by task_work, run it to clear
+	 * TIF_NOTIFY_SIGNAL. The caller will retry if necessary.
+	 */
+	clear_notify_signal();
+	if (unlikely(READ_ONCE(current->task_works)))
+		task_work_run();
 }
 
 static int ptrace_signal(int signr, kernel_siginfo_t *info)
-- 
2.43.0

Re: FAILED: patch "[PATCH] kernel: rerun task_work while freezing in get_signal()" failed to apply to 5.15-stable tree

[Greg KH]

On Mon, Jul 29, 2024 at 12:02:01PM -0600, Jens Axboe wrote:
> On 7/29/24 1:49 AM, gregkh@linuxfoundation.org wrote:
> > 
> > The patch below does not apply to the 5.15-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-5.15.y
> > git checkout FETCH_HEAD
> > git cherry-pick -x 943ad0b62e3c21f324c4884caa6cb4a871bca05c
> > # <resolve conflicts, build, test, etc.>
> > git commit -s
> > git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024072940-parish-shirt-3e49@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
> 
> Here's the 5.10-stable and 5.15-stable variant of this. For some
> reason this wasn't queued for 5.10 (probably because of the long
> ago 5.15-stable backport of io_uring to 5.10), but it should go
> there too.

Now queued up, thanks.

greg k-h