diff mbox series

[5.10,5.4,4.19,4.14] watchdog: sbsa_wdog: Make sure the timeout programming is within the limits

Message ID 20230413204823.724485-1-code@tyhicks.com
State New
Headers show
Series [5.10,5.4,4.19,4.14] watchdog: sbsa_wdog: Make sure the timeout programming is within the limits | expand

Commit Message

Tyler Hicks April 13, 2023, 8:48 p.m. UTC 
From: George Cherian <george.cherian@marvell.com>

[ Upstream commit 000987a38b53c172f435142a4026dd71378ca464 ]

Make sure to honour the max_hw_heartbeat_ms while programming the timeout
value to WOR. Clamp the timeout passed to sbsa_gwdt_set_timeout() to
make sure the programmed value is within the permissible range.

Fixes: abd3ac7902fb ("watchdog: sbsa: Support architecture version 1")

Signed-off-by: George Cherian <george.cherian@marvell.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230209021117.1512097-1-george.cherian@marvell.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Signed-off-by: Tyler Hicks (Microsoft) <code@tyhicks.com>
---

The Fixes line in the original commit is incorrect. This commit fixes a
bug that goes all the way back to v4.6 commit 57d2caaabfc7 ("Watchdog:
introduce ARM SBSA watchdog driver") when only 32-bit Watchdog Offset
Registers (WOR) were supported.

Without this fix, there's a truncation on the first argument, of u32
type, passed to writel() in the following situation situation:

Generic Watchdog architecture version is 1 (WOR is 32-bit)
action is 1
timeout is 240s
CNTFRQ_EL0 is 25000050 Hz
wdd.max_hw_heartbeat_ms is 171s

25000050 * 240 = 6000012000  <--- requires 33 bits to store
6000012000 & 0xFFFFFFFF = 1705044704  <--- truncated value written to WOR
1705044704 / 25000050 = 68.2s  <--- timeout incorrectly set to 68.2s

The timeout from userspace is greater than wdd.max_hw_heartbeat_ms so
the watchdog core pings at 69s (240 - 171) which results in
intermittent and unexpected panics (action=1).

With this patch applied, the timeout passed to writel() never exceeds
32-bits and the watchdog core + systemd keeps the watchdog happy.

I've validated this fix on real hardware running a linux-5.10.y stable
kernel. Please apply this patch to 5.10 through 4.14. Thanks!

Tyler

 drivers/watchdog/sbsa_gwdt.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Guenter Roeck April 14, 2023, 12:13 a.m. UTC | #1 
On 4/13/23 13:48, Tyler Hicks (Microsoft) wrote:
> From: George Cherian <george.cherian@marvell.com>
> 
> [ Upstream commit 000987a38b53c172f435142a4026dd71378ca464 ]
> 
> Make sure to honour the max_hw_heartbeat_ms while programming the timeout
> value to WOR. Clamp the timeout passed to sbsa_gwdt_set_timeout() to
> make sure the programmed value is within the permissible range.
> 
> Fixes: abd3ac7902fb ("watchdog: sbsa: Support architecture version 1")
> 
> Signed-off-by: George Cherian <george.cherian@marvell.com>
> Reviewed-by: Guenter Roeck <linux@roeck-us.net>
> Link: https://lore.kernel.org/r/20230209021117.1512097-1-george.cherian@marvell.com
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
> Signed-off-by: Tyler Hicks (Microsoft) <code@tyhicks.com>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> 
> The Fixes line in the original commit is incorrect. This commit fixes a
> bug that goes all the way back to v4.6 commit 57d2caaabfc7 ("Watchdog:
> introduce ARM SBSA watchdog driver") when only 32-bit Watchdog Offset
> Registers (WOR) were supported.
> 
> Without this fix, there's a truncation on the first argument, of u32
> type, passed to writel() in the following situation situation:
> 
> Generic Watchdog architecture version is 1 (WOR is 32-bit)
> action is 1
> timeout is 240s
> CNTFRQ_EL0 is 25000050 Hz
> wdd.max_hw_heartbeat_ms is 171s
> 
> 25000050 * 240 = 6000012000  <--- requires 33 bits to store
> 6000012000 & 0xFFFFFFFF = 1705044704  <--- truncated value written to WOR
> 1705044704 / 25000050 = 68.2s  <--- timeout incorrectly set to 68.2s
> 
> The timeout from userspace is greater than wdd.max_hw_heartbeat_ms so
> the watchdog core pings at 69s (240 - 171) which results in
> intermittent and unexpected panics (action=1).
> 
> With this patch applied, the timeout passed to writel() never exceeds
> 32-bits and the watchdog core + systemd keeps the watchdog happy.
> 
> I've validated this fix on real hardware running a linux-5.10.y stable
> kernel. Please apply this patch to 5.10 through 4.14. Thanks!
> 
> Tyler
> 
>   drivers/watchdog/sbsa_gwdt.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/watchdog/sbsa_gwdt.c b/drivers/watchdog/sbsa_gwdt.c
> index f0f1e3b2e463..4cbe6ba52754 100644
> --- a/drivers/watchdog/sbsa_gwdt.c
> +++ b/drivers/watchdog/sbsa_gwdt.c
> @@ -121,6 +121,7 @@ static int sbsa_gwdt_set_timeout(struct watchdog_device *wdd,
>   	struct sbsa_gwdt *gwdt = watchdog_get_drvdata(wdd);
>   
>   	wdd->timeout = timeout;
> +	timeout = clamp_t(unsigned int, timeout, 1, wdd->max_hw_heartbeat_ms / 1000);
>   
>   	if (action)
>   		writel(gwdt->clk * timeout,
diff mbox series

Patch

diff --git a/drivers/watchdog/sbsa_gwdt.c b/drivers/watchdog/sbsa_gwdt.c
index f0f1e3b2e463..4cbe6ba52754 100644
--- a/drivers/watchdog/sbsa_gwdt.c
+++ b/drivers/watchdog/sbsa_gwdt.c
@@ -121,6 +121,7 @@  static int sbsa_gwdt_set_timeout(struct watchdog_device *wdd,
 	struct sbsa_gwdt *gwdt = watchdog_get_drvdata(wdd);
 
 	wdd->timeout = timeout;
+	timeout = clamp_t(unsigned int, timeout, 1, wdd->max_hw_heartbeat_ms / 1000);
 
 	if (action)
 		writel(gwdt->clk * timeout,