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| author |   Guenter Roeck <linux@roeck-us.net> | 2017-09-25 09:17:01 -0700 |
|---|---|---|
| committer |   Wim Van Sebroeck <wim@iguana.be> | 2017-12-17 11:01:47 +0100 |
| commit | 4bcd615fad6adddc68b058d498b30a9e0e0db77a (patch) | |
| tree | 2147795c91515080182841b24959a0416bcae594 /drivers/watchdog/watchdog_dev.c | |
| parent | Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma (diff) | |
| download | linux-dev-4bcd615fad6adddc68b058d498b30a9e0e0db77a.tar.xz linux-dev-4bcd615fad6adddc68b058d498b30a9e0e0db77a.zip | |
watchdog: Fix potential kref imbalance when opening watchdog
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: ee142889e32f5 ("watchdog: Introduce WDOG_HW_RUNNING flag")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Diffstat (limited to 'drivers/watchdog/watchdog_dev.c')
| -rw-r--r-- | drivers/watchdog/watchdog_dev.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c index 1e971a50d7fb..12fe47d8237b 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -769,6 +769,7 @@ static int watchdog_open(struct inode *inode, struct file *file) { struct watchdog_core_data *wd_data; struct watchdog_device *wdd; + bool hw_running; int err; /* Get the corresponding watchdog device */ @@ -788,7 +789,8 @@ static int watchdog_open(struct inode *inode, struct file *file) * If the /dev/watchdog device is open, we don't want the module * to be unloaded. */ - if (!watchdog_hw_running(wdd) && !try_module_get(wdd->ops->owner)) { + hw_running = watchdog_hw_running(wdd); + if (!hw_running && !try_module_get(wdd->ops->owner)) { err = -EBUSY; goto out_clear; } @@ -799,7 +801,7 @@ static int watchdog_open(struct inode *inode, struct file *file) file->private_data = wd_data; - if (!watchdog_hw_running(wdd)) + if (!hw_running) kref_get(&wd_data->kref); /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ |