linux-kernel - [PATCH] ppp: Fix deadlock caused by unsafe-irq lock in ap

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Date: Fri, 19 Apr 2024 02:59:10 +0900
From: Jeongjun Park <aha310510@...il.com>
To: davem@...emloft.net
Cc: edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	linux-kernel@...r.kernel.org,
	linux-ppp@...r.kernel.org,
	netdev@...r.kernel.org,
	syzkaller-bugs@...glegroups.com,
	syzbot+393d0ef63475d9bb1f16@...kaller.appspotmail.com,
	Jeongjun Park <aha310510@...il.com>
Subject: [PATCH] ppp: Fix deadlock caused by unsafe-irq lock in ap_get()


read_lock() present in ap_get() is interrupt-vulnerable, so the function needs to be modified.


Reported-by: syzbot+393d0ef63475d9bb1f16@...kaller.appspotmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jeongjun Park <aha310510@...il.com>
---
 drivers/net/ppp/ppp_async.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ppp/ppp_async.c b/drivers/net/ppp/ppp_async.c
index c33c3db3cc08..dc1d4633428a 100644
--- a/drivers/net/ppp/ppp_async.c
+++ b/drivers/net/ppp/ppp_async.c
@@ -133,12 +133,13 @@ static DEFINE_RWLOCK(disc_data_lock);
 static struct asyncppp *ap_get(struct tty_struct *tty)
 {
 	struct asyncppp *ap;
+	unsigned long flags;
 
-	read_lock(&disc_data_lock);
+	flags = read_lock_irqsave(&disc_data_lock);
 	ap = tty->disc_data;
 	if (ap != NULL)
 		refcount_inc(&ap->refcnt);
-	read_unlock(&disc_data_lock);
+	read_unlock_irqrestore(&disc_data_lock, flags);
 	return ap;
 }
 
-- 
2.34.1