FAILED: patch "[PATCH] pid_namespace: make zap_pid_ns_processes() freezable" failed to apply to 6.1-stable tree

FAILED: patch "[PATCH] pid_namespace: make zap_pid_ns_processes() freezable" failed to apply to 6.1-stable tree

[gregkh]

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 81933038f5e273d17ed22792f906889393b204c5
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026102100-lifter-velcro-2a2c@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 81933038f5e273d17ed22792f906889393b204c5 Mon Sep 17 00:00:00 2001
From: Aviv Vaknin <vaknins33@gmail.com>
Date: Fri, 2 Oct 2026 23:28:20 +0300
Subject: [PATCH] pid_namespace: make zap_pid_ns_processes() freezable

When the init of a pid namespace exits, zap_pid_ns_processes() waits
until all other pids in the namespace are freed. A tracer outside the
namespace that does not reap its traced zombies keeps those pids
allocated, so this wait has no upper bound, and while it lasts every
suspend attempt fails:

  Freezing user space processes failed after 20.006 seconds (2 tasks refusing to freeze, wq_busy=0):

Neither wait is freezable. The first loop sleeps in do_wait(), which
returns -ERESTARTSYS on the freezer's fake signal; the loop then clears
TIF_SIGPENDING and waits again without ever freezing. The final loop
sleeps in TASK_INTERRUPTIBLE, and since nothing clears TIF_SIGPENDING
there, schedule() returns immediately after the first freeze attempt
and the task spins until the wait ends.

Sleep in TASK_INTERRUPTIBLE | TASK_FREEZABLE in do_wait(), so that the
freezer can freeze tasks waiting there directly, and in TASK_IDLE |
TASK_FREEZABLE in the final loop, like coredump_task_exit() does.

This was hit with Chromium-based browsers: crashpad ptrace-attaches the
threads of a crashed renderer, which is a pid namespace init, and does
not reap those killed during the dump.

Fixes: 3eb07c8c8adb ("pid namespaces: destroy pid namespace on init's death")
Fixes: b9a985db9896 ("pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes")
Cc: stable@vger.kernel.org # 6.1+
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Aviv Vaknin <vaknins33@gmail.com>
Link: https://patch.msgid.link/20261002202820.3433318-1-vaknins33@gmail.com
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Bradley Morgan <brads@mainlining.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

diff --git a/kernel/exit.c b/kernel/exit.c
index 282328d2b4cf..ba1469bea8fb 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1729,7 +1729,7 @@ static long do_wait(struct wait_opts *wo)
 	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
 
 	do {
-		set_current_state(TASK_INTERRUPTIBLE);
+		set_current_state(TASK_INTERRUPTIBLE | TASK_FREEZABLE);
 		retval = __do_wait(wo);
 		if (retval != -ERESTARTSYS)
 			break;
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index d36afc58ee1d..4ade0f37ed54 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -268,7 +268,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 	 * free_pid() will awaken this task.
 	 */
 	for (;;) {
-		set_current_state(TASK_INTERRUPTIBLE);
+		set_current_state(TASK_IDLE | TASK_FREEZABLE);
 		if (pid_ns->pid_allocated == init_pids)
 			break;
 		schedule();

[PATCH 6.1.y 1/2] exit: move core of do_wait() into helper

[Sasha Levin]

From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit 06a101ca45b296fe951692620b0bc49abf90c368 ]

Rather than have a maze of gotos, put the actual logic in __do_wait()
and have do_wait() loop deal with waitqueue setup/teardown and whether
to call __do_wait() again.

No functional changes intended in this patch.

Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: 81933038f5e2 ("pid_namespace: make zap_pid_ns_processes() freezable")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/exit.c | 51 +++++++++++++++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 20 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 413540df3e185..d4addbc7aff20 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1588,16 +1588,10 @@ static int do_wait_pid(struct wait_opts *wo)
 	return 0;
 }
 
-static long do_wait(struct wait_opts *wo)
+static long __do_wait(struct wait_opts *wo)
 {
-	int retval;
-
-	trace_sched_process_wait(wo->wo_pid);
+	long retval;
 
-	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
-	wo->child_wait.private = current;
-	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
-repeat:
 	/*
 	 * If there is nothing that can match our criteria, just get out.
 	 * We will clear ->notask_error to zero if we see any child that
@@ -1609,24 +1603,23 @@ static long do_wait(struct wait_opts *wo)
 	   (!wo->wo_pid || !pid_has_task(wo->wo_pid, wo->wo_type)))
 		goto notask;
 
-	set_current_state(TASK_INTERRUPTIBLE);
 	read_lock(&tasklist_lock);
 
 	if (wo->wo_type == PIDTYPE_PID) {
 		retval = do_wait_pid(wo);
 		if (retval)
-			goto end;
+			return retval;
 	} else {
 		struct task_struct *tsk = current;
 
 		do {
 			retval = do_wait_thread(wo, tsk);
 			if (retval)
-				goto end;
+				return retval;
 
 			retval = ptrace_do_wait(wo, tsk);
 			if (retval)
-				goto end;
+				return retval;
 
 			if (wo->wo_flags & __WNOTHREAD)
 				break;
@@ -1636,14 +1629,32 @@ static long do_wait(struct wait_opts *wo)
 
 notask:
 	retval = wo->notask_error;
-	if (!retval && !(wo->wo_flags & WNOHANG)) {
-		retval = -ERESTARTSYS;
-		if (!signal_pending(current)) {
-			schedule();
-			goto repeat;
-		}
-	}
-end:
+	if (!retval && !(wo->wo_flags & WNOHANG))
+		return -ERESTARTSYS;
+
+	return retval;
+}
+
+static long do_wait(struct wait_opts *wo)
+{
+	int retval;
+
+	trace_sched_process_wait(wo->wo_pid);
+
+	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
+	wo->child_wait.private = current;
+	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
+
+	do {
+		set_current_state(TASK_INTERRUPTIBLE);
+		retval = __do_wait(wo);
+		if (retval != -ERESTARTSYS)
+			break;
+		if (signal_pending(current))
+			break;
+		schedule();
+	} while (1);
+
 	__set_current_state(TASK_RUNNING);
 	remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
 	return retval;
-- 
2.53.0

[PATCH 6.1.y 2/2] pid_namespace: make zap_pid_ns_processes() freezable

[Sasha Levin]

From: Aviv Vaknin <vaknins33@gmail.com>

[ Upstream commit 81933038f5e273d17ed22792f906889393b204c5 ]

When the init of a pid namespace exits, zap_pid_ns_processes() waits
until all other pids in the namespace are freed. A tracer outside the
namespace that does not reap its traced zombies keeps those pids
allocated, so this wait has no upper bound, and while it lasts every
suspend attempt fails:

  Freezing user space processes failed after 20.006 seconds (2 tasks refusing to freeze, wq_busy=0):

Neither wait is freezable. The first loop sleeps in do_wait(), which
returns -ERESTARTSYS on the freezer's fake signal; the loop then clears
TIF_SIGPENDING and waits again without ever freezing. The final loop
sleeps in TASK_INTERRUPTIBLE, and since nothing clears TIF_SIGPENDING
there, schedule() returns immediately after the first freeze attempt
and the task spins until the wait ends.

Sleep in TASK_INTERRUPTIBLE | TASK_FREEZABLE in do_wait(), so that the
freezer can freeze tasks waiting there directly, and in TASK_IDLE |
TASK_FREEZABLE in the final loop, like coredump_task_exit() does.

This was hit with Chromium-based browsers: crashpad ptrace-attaches the
threads of a crashed renderer, which is a pid namespace init, and does
not reap those killed during the dump.

Fixes: 3eb07c8c8adb ("pid namespaces: destroy pid namespace on init's death")
Fixes: b9a985db9896 ("pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes")
Cc: stable@vger.kernel.org # 6.1+
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Aviv Vaknin <vaknins33@gmail.com>
Link: https://patch.msgid.link/20261002202820.3433318-1-vaknins33@gmail.com
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Bradley Morgan <brads@mainlining.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/exit.c          | 2 +-
 kernel/pid_namespace.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index d4addbc7aff20..b3cfeba72dc02 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1646,7 +1646,7 @@ static long do_wait(struct wait_opts *wo)
 	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
 
 	do {
-		set_current_state(TASK_INTERRUPTIBLE);
+		set_current_state(TASK_INTERRUPTIBLE | TASK_FREEZABLE);
 		retval = __do_wait(wo);
 		if (retval != -ERESTARTSYS)
 			break;
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index a575fabf697eb..cd3ee747649db 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -242,7 +242,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 	 * free_pid() will awaken this task.
 	 */
 	for (;;) {
-		set_current_state(TASK_INTERRUPTIBLE);
+		set_current_state(TASK_IDLE | TASK_FREEZABLE);
 		if (pid_ns->pid_allocated == init_pids)
 			break;
 		/*
-- 
2.53.0