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From: Stanislav German-Evtushenko <ginermail@gmail.com>
To: Wim Van Sebroeck <wim@linux-watchdog.org>,
	Guenter Roeck <linux@roeck-us.net>
Cc: linux-watchdog@vger.kernel.org,
	Stanislav German-Evtushenko <ginermail@gmail.com>
Subject: [PATCH] watchdog: Device must be opened for writing
Date: Sun, 15 Aug 2021 04:13:45 +0900	[thread overview]
Message-ID: <20210814191345.27221-1-ginermail@gmail.com> (raw)

If userspace opens the watchdog device self-feeding stops. Sometimes
opening the device happens by accident, e.g. by mistakenly running grep
recursively in a wrong directory which leads to the server being reset.

Watchdog device does not handle read operation therefore the issue can be
prevented by requiring the device to be opened for writing:

- Prevent opening the device without FMODE_WRITE

Signed-off-by: Stanislav German-Evtushenko <ginermail@gmail.com>
---
 drivers/watchdog/watchdog_dev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 3bab32485273..28b88542a4d0 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -835,6 +835,10 @@ static int watchdog_open(struct inode *inode, struct file *file)
 	bool hw_running;
 	int err;
 
+	/* Must be open for writing */
+	if (!(file->f_mode & FMODE_WRITE))
+		return -EINVAL;
+
 	/* Get the corresponding watchdog device */
 	if (imajor(inode) == MISC_MAJOR)
 		wd_data = old_wd_data;

base-commit: cf813c67d9619fd474c785698cbed543b94209dd
-- 
2.25.1


             reply	other threads:[~2021-08-14 19:14 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-14 19:13 Stanislav German-Evtushenko [this message]
2021-08-14 19:56 ` Guenter Roeck
     [not found]   ` <CAPeRZrV+HwdmBKFB3tmG_tEHjsR8h3WLxKQYGDLOLgw178oq=A@mail.gmail.com>
2021-08-15  1:33     ` Guenter Roeck
2021-08-15  4:32       ` Stanislav German-Evtushenko

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