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watchdog: s3c2410: Fix potential deadlock on &wdt->lock

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As &wdt->lock is acquired by hard irq s3c2410wdt_irq(),
other acquisition of the same lock under process context should
disable irq, otherwise deadlock could happen if the
irq preempt the execution while the lock is held in process context
on the same CPU.

[Deadlock Scenario]
s3c2410wdt_suspend()
    -> s3c2410wdt_stop()
    -> spin_lock(&wdt->lock)
        <irq iterrupt>
        -> s3c2410wdt_irq()
        -> s3c2410wdt_keepalive()
        -> spin_lock(&wdt->lock) (deadlock here)

[Deadlock Scenario]
s3c2410wdt_probe()
    -> s3c2410wdt_start()
    -> spin_lock(&wdt->lock)
        <irq iterrupt>
        -> s3c2410wdt_irq()
        -> s3c2410wdt_keepalive()
        -> spin_lock(&wdt->lock) (deadlock here)

[Deadlock Scenario]
s3c2410wdt_keepalive()
    -> spin_lock(&wdt->lock)
        <irq iterrupt>
        -> s3c2410wdt_irq()
        -> s3c2410wdt_keepalive()
        -> spin_lock(&wdt->lock) (deadlock here)

This flaw was found by an experimental static analysis tool I am
developing for irq-related deadlock, which reported the above
warning when analyzing the linux kernel 6.4-rc7 release.

The tentative patch fix the potential deadlock by spin_lock_irqsave()
under process context.

Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230705090951.63762-1-dg573847474@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
This commit is contained in:
Chengfeng Ye 2023-07-05 09:09:51 +00:00 committed by Wim Van Sebroeck
parent f20ca595ae
commit aeb3ef51b6
1 changed files with 9 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/watchdog/s3c2410_wdt.c
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@ -378,10 +378,11 @@ static int s3c2410wdt_enable(struct s3c2410_wdt *wdt, bool en)
static int s3c2410wdt_keepalive(struct watchdog_device *wdd)
{
struct s3c2410_wdt *wdt = watchdog_get_drvdata(wdd);
unsigned long flags;
spin_lock(&wdt->lock);
spin_lock_irqsave(&wdt->lock, flags);
writel(wdt->count, wdt->reg_base + S3C2410_WTCNT);
spin_unlock(&wdt->lock);
spin_unlock_irqrestore(&wdt->lock, flags);
return 0;
}
@ -398,10 +399,11 @@ static void __s3c2410wdt_stop(struct s3c2410_wdt *wdt)
static int s3c2410wdt_stop(struct watchdog_device *wdd)
{
struct s3c2410_wdt *wdt = watchdog_get_drvdata(wdd);
unsigned long flags;
spin_lock(&wdt->lock);
spin_lock_irqsave(&wdt->lock, flags);
__s3c2410wdt_stop(wdt);
spin_unlock(&wdt->lock);
spin_unlock_irqrestore(&wdt->lock, flags);
return 0;
}
@ -410,8 +412,9 @@ static int s3c2410wdt_start(struct watchdog_device *wdd)
{
unsigned long wtcon;
struct s3c2410_wdt *wdt = watchdog_get_drvdata(wdd);
unsigned long flags;
spin_lock(&wdt->lock);
spin_lock_irqsave(&wdt->lock, flags);
__s3c2410wdt_stop(wdt);
@ -432,7 +435,7 @@ static int s3c2410wdt_start(struct watchdog_device *wdd)
writel(wdt->count, wdt->reg_base + S3C2410_WTDAT);
writel(wdt->count, wdt->reg_base + S3C2410_WTCNT);
writel(wtcon, wdt->reg_base + S3C2410_WTCON);
spin_unlock(&wdt->lock);
spin_unlock_irqrestore(&wdt->lock, flags);
return 0;
}