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watchdog: Fix potential kref imbalance when opening watchdog
[ Upstream commit4bcd615fad
] If a watchdog driver's open function sets WDOG_HW_RUNNING with the expectation that the watchdog can not be stopped, but then stops the watchdog anyway in its stop function, kref_get() wil not be called in watchdog_open(). If the watchdog then stops on close, WDOG_HW_RUNNING will be cleared and kref_put() will be called, causing a kref imbalance. As result the character device data structure will be released, which in turn will cause the system to crash on the next call to watchdog_open(). Fixes:ee142889e3
("watchdog: Introduce WDOG_HW_RUNNING flag") Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Wim Van Sebroeck <wim@iguana.be> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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parent
008029510a
commit
08b8109010
1 changed files with 4 additions and 2 deletions
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@ -768,6 +768,7 @@ static int watchdog_open(struct inode *inode, struct file *file)
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{
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struct watchdog_core_data *wd_data;
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struct watchdog_device *wdd;
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bool hw_running;
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int err;
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/* Get the corresponding watchdog device */
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@ -787,7 +788,8 @@ static int watchdog_open(struct inode *inode, struct file *file)
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* If the /dev/watchdog device is open, we don't want the module
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* to be unloaded.
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*/
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if (!watchdog_hw_running(wdd) && !try_module_get(wdd->ops->owner)) {
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hw_running = watchdog_hw_running(wdd);
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if (!hw_running && !try_module_get(wdd->ops->owner)) {
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err = -EBUSY;
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goto out_clear;
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}
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@ -798,7 +800,7 @@ static int watchdog_open(struct inode *inode, struct file *file)
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file->private_data = wd_data;
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if (!watchdog_hw_running(wdd))
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if (!hw_running)
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kref_get(&wd_data->kref);
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/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
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