linux-kernel - [PATCH] dma-buf/sw-sync: don't enable IRQ from sync_print

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Date: Sun, 5 May 2024 23:08:31 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: syzbot <syzbot+a225ee3df7e7f9372dbe@...kaller.appspotmail.com>,
        syzkaller-bugs@...glegroups.com,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Christian Konig <christian.koenig@....com>,
        Sean Paul
 <seanpaul@...omium.org>,
        Chris Wilson <chris@...is-wilson.co.uk>
Cc: linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linaro-mm-sig@...ts.linaro.org, dri-devel@...ts.freedesktop.org
Subject: [PATCH] dma-buf/sw-sync: don't enable IRQ from sync_print_obj()

Since commit a6aa8fca4d79 ("dma-buf/sw-sync: Reduce irqsave/irqrestore from
known context") by error replaced spin_unlock_irqrestore() with
spin_unlock_irq() for both sync_debugfs_show() and sync_print_obj() despite
sync_print_obj() is called from sync_debugfs_show(), lockdep complains
inconsistent lock state warning.

Use plain spin_{lock,unlock}() for sync_print_obj(), for
sync_debugfs_show() is already using spin_{lock,unlock}_irq().

Reported-by: syzbot <syzbot+a225ee3df7e7f9372dbe@...kaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=a225ee3df7e7f9372dbe
Fixes: a6aa8fca4d79 ("dma-buf/sw-sync: Reduce irqsave/irqrestore from known context")
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 drivers/dma-buf/sync_debug.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/sync_debug.c b/drivers/dma-buf/sync_debug.c
index 101394f16930..237bce21d1e7 100644
--- a/drivers/dma-buf/sync_debug.c
+++ b/drivers/dma-buf/sync_debug.c
@@ -110,12 +110,12 @@ static void sync_print_obj(struct seq_file *s, struct sync_timeline *obj)
 
 	seq_printf(s, "%s: %d\n", obj->name, obj->value);
 
-	spin_lock_irq(&obj->lock);
+	spin_lock(&obj->lock); /* Caller already disabled IRQ. */
 	list_for_each(pos, &obj->pt_list) {
 		struct sync_pt *pt = container_of(pos, struct sync_pt, link);
 		sync_print_fence(s, &pt->base, false);
 	}
-	spin_unlock_irq(&obj->lock);
+	spin_unlock(&obj->lock);
 }
 
 static void sync_print_sync_file(struct seq_file *s,
-- 
2.18.4