FAILED: patch "[PATCH] debugobjects: Do not fill_pool() if pi_blocked_on" failed to apply to 6.1-stable tree

FAILED: patch "[PATCH] debugobjects: Do not fill_pool() if pi_blocked_on" 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 5f41161059fd0f1bbf18c90f3180e38cc45a14eb
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026061611-defective-unbundle-fbc8@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 5f41161059fd0f1bbf18c90f3180e38cc45a14eb Mon Sep 17 00:00:00 2001
From: Helen Koike <koike@igalia.com>
Date: Mon, 11 May 2026 18:53:05 -0300
Subject: [PATCH] debugobjects: Do not fill_pool() if pi_blocked_on

On RT enabled kernels, fill_pool() ends up calling rtlock_lock(), which
asserts if current::pi_blocked_on is set, because a task can obviously only
block on one lock as otherwise the priority inheritenace chain gets
corrupted.

Prevent this by expanding the conditional to take current::pi_blocked_on
into account.

Fixes: 4bedcc28469a ("debugobjects: Make them PREEMPT_RT aware")
Reported-by: syzbot+b8ca586b9fc235f0c0df@syzkaller.appspotmail.com
Signed-off-by: Helen Koike <koike@igalia.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260511215359.3351259-1-koike@igalia.com
Closes: https://syzkaller.appspot.com/bug?extid=b8ca586b9fc235f0c0df

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 12e2e42e6a31..772ddabcbe7d 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -711,6 +711,15 @@ static struct debug_obj *lookup_object_or_alloc(void *addr, struct debug_bucket
 	return NULL;
 }
 
+static inline bool debug_objects_is_pi_blocked_on(void)
+{
+#ifdef CONFIG_RT_MUTEXES
+	return current->pi_blocked_on != NULL;
+#else
+	return false;
+#endif
+}
+
 static void debug_objects_fill_pool(void)
 {
 	if (!static_branch_likely(&obj_cache_enabled))
@@ -727,11 +736,12 @@ static void debug_objects_fill_pool(void)
 
 	/*
 	 * On RT enabled kernels the pool refill must happen in preemptible
-	 * context -- for !RT kernels we rely on the fact that spinlock_t and
-	 * raw_spinlock_t are basically the same type and this lock-type
-	 * inversion works just fine.
+	 * context and not enqueued on an rt_mutex -- for !RT kernels we rely
+	 * on the fact that spinlock_t and raw_spinlock_t are basically the
+	 * same type and this lock-type inversion works just fine.
 	 */
-	if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible() || system_state < SYSTEM_SCHEDULING) {
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT) || system_state < SYSTEM_SCHEDULING ||
+	    (preemptible() && !debug_objects_is_pi_blocked_on())) {
 		/*
 		 * Annotate away the spinlock_t inside raw_spinlock_t warning
 		 * by temporarily raising the wait-type to LD_WAIT_CONFIG, matching

[PATCH 6.1.y] debugobjects: Do not fill_pool() if pi_blocked_on

[Sasha Levin]

From: Helen Koike <koike@igalia.com>

[ Upstream commit 5f41161059fd0f1bbf18c90f3180e38cc45a14eb ]

On RT enabled kernels, fill_pool() ends up calling rtlock_lock(), which
asserts if current::pi_blocked_on is set, because a task can obviously only
block on one lock as otherwise the priority inheritenace chain gets
corrupted.

Prevent this by expanding the conditional to take current::pi_blocked_on
into account.

Fixes: 4bedcc28469a ("debugobjects: Make them PREEMPT_RT aware")
Reported-by: syzbot+b8ca586b9fc235f0c0df@syzkaller.appspotmail.com
Signed-off-by: Helen Koike <koike@igalia.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260511215359.3351259-1-koike@igalia.com
Closes: https://syzkaller.appspot.com/bug?extid=b8ca586b9fc235f0c0df
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 lib/debugobjects.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 8c3b483a8fb44a..f9d53a0af4238f 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -597,13 +597,23 @@ static struct debug_obj *lookup_object_or_alloc(void *addr, struct debug_bucket
 	return NULL;
 }
 
+static inline bool debug_objects_is_pi_blocked_on(void)
+{
+#ifdef CONFIG_RT_MUTEXES
+	return current->pi_blocked_on != NULL;
+#else
+	return false;
+#endif
+}
+
 static void debug_objects_fill_pool(void)
 {
 	/*
 	 * On RT enabled kernels the pool refill must happen in preemptible
-	 * context:
+	 * context and not enqueued on an rt_mutex:
 	 */
-	if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible())
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT) ||
+	    (preemptible() && !debug_objects_is_pi_blocked_on()))
 		fill_pool();
 }
 
-- 
2.53.0