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Mon, 08 Jun 2026 14:04:21 -0700 (PDT) From: Rosen Penev To: linux-watchdog@vger.kernel.org Cc: Wim Van Sebroeck , Guenter Roeck , linux-kernel@vger.kernel.org (open list) Subject: [PATCHv3 1/2] watchdog: pika_wdt: fix timer lifecycle bugs Date: Mon, 8 Jun 2026 14:04:01 -0700 Message-ID: <20260608210402.31545-2-rosenp@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260608210402.31545-1-rosenp@gmail.com> References: <20260608210402.31545-1-rosenp@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Two timer lifecycle bugs in the PIKA watchdog driver: 1. pikawdt_release() clears the open bit before stopping the timer, allowing a concurrent pikawdt_open() to start a new timer that is then immediately deleted. Move clear_bit after the timer stop. Use timer_shutdown_sync() so the handler cannot re-arm after the call returns. Add timer_setup() in pikawdt_open() to re-initialize the timer for the next open. 2. pikawdt_exit() unmaps FPGA IO memory without first stopping the ping timer. If the timer handler fires after iounmap(), it executes pikawdt_ping() on freed memory. Use timer_shutdown_sync() which permanently prevents re-arming. Assisted-by: opencode:big-pickle Signed-off-by: Rosen Penev --- drivers/watchdog/pika_wdt.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/watchdog/pika_wdt.c b/drivers/watchdog/pika_wdt.c index 87b8988d2520..d567103ec5e4 100644 --- a/drivers/watchdog/pika_wdt.c +++ b/drivers/watchdog/pika_wdt.c @@ -117,6 +117,7 @@ static int pikawdt_open(struct inode *inode, struct file *file) if (test_and_set_bit(0, &pikawdt_private.open)) return -EBUSY; + timer_setup(&pikawdt_private.timer, pikawdt_ping, 0); pikawdt_start(); return stream_open(inode, file); @@ -129,7 +130,7 @@ static int pikawdt_release(struct inode *inode, struct file *file) { /* stop internal ping */ if (!pikawdt_private.expect_close) - timer_delete(&pikawdt_private.timer); + timer_shutdown_sync(&pikawdt_private.timer); clear_bit(0, &pikawdt_private.open); pikawdt_private.expect_close = 0; @@ -291,6 +292,7 @@ static void __exit pikawdt_exit(void) { misc_deregister(&pikawdt_miscdev); + timer_shutdown_sync(&pikawdt_private.timer); iounmap(pikawdt_private.fpga); } -- 2.54.0