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authorChengfeng Ye <dg573847474@gmail.com>2023-07-05 09:09:51 +0000
committerWim Van Sebroeck <wim@linux-watchdog.org>2023-08-19 17:14:37 +0200
commitaeb3ef51b602dce456c850414aa1becd0e7aeab1 (patch)
tree311b8fe5a1a74d48148310f03093e6bebb49d977 /drivers/watchdog
parentf20ca595ae23314db0383940a184317333c46662 (diff)
watchdog: s3c2410: Fix potential deadlock on &wdt->lock
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>
Diffstat (limited to 'drivers/watchdog')
-rw-r--r--drivers/watchdog/s3c2410_wdt.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
index 2bcc8faa7fa5..0b4bd883ff28 100644
--- a/drivers/watchdog/s3c2410_wdt.c
+++ b/drivers/watchdog/s3c2410_wdt.c
@@ -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;
}