linux-kernel - [PATCH net] eventpoll: Annotate data-race of busy_poll

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Message-Id: <20240806123301.167557-1-jdamato@fastly.com>
Date: Tue,  6 Aug 2024 12:33:01 +0000
From: Joe Damato <jdamato@...tly.com>
To: linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Cc: netdev@...r.kernel.org,
	Martin Karsten <mkarsten@...terloo.ca>,
	stable@...r.kernel.org,
	Joe Damato <jdamato@...tly.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>,
	Stanislav Fomichev <sdf@...ichev.me>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net] eventpoll: Annotate data-race of busy_poll_usecs

From: Martin Karsten <mkarsten@...terloo.ca>

A struct eventpoll's busy_poll_usecs field can be modified via a user
ioctl at any time. All reads of this field should be annotated with
READ_ONCE.

Fixes: 85455c795c07 ("eventpoll: support busy poll per epoll instance")
Cc: stable@...r.kernel.org
Signed-off-by: Martin Karsten <mkarsten@...terloo.ca>
Reviewed-by: Joe Damato <jdamato@...tly.com>
---
 fs/eventpoll.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index f53ca4f7fced..6d0e2f547ae7 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -420,7 +420,7 @@ static bool busy_loop_ep_timeout(unsigned long start_time,
 
 static bool ep_busy_loop_on(struct eventpoll *ep)
 {
-	return !!ep->busy_poll_usecs || net_busy_loop_on();
+	return !!READ_ONCE(ep->busy_poll_usecs) || net_busy_loop_on();
 }
 
 static bool ep_busy_loop_end(void *p, unsigned long start_time)
-- 
2.25.1