[PATCH v3] drm: Fix potential overflow issue in event_string array

[jiangfeng at kylinos.cn]

From: Feng Jiang <jiangfeng at kylinos.cn>

When calling scnprintf() to append recovery method to event_string,
the second argument should be `sizeof(event_string) - len`, otherwise
there is a potential overflow problem.

Fixes: b7cf9f4ac1b8 ("drm: Introduce device wedged event")
Signed-off-by: Feng Jiang <jiangfeng at kylinos.cn>
---
v3:
- update the subject

v2:
- update commit message
- keep scnprintf() as a single line
---
 drivers/gpu/drm/drm_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 17fc5dc708f4..60e5ac179c15 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -549,7 +549,7 @@ int drm_dev_wedged_event(struct drm_device *dev, unsigned long method)
 		if (drm_WARN_ONCE(dev, !recovery, "invalid recovery method %u\n", opt))
 			break;
 
-		len += scnprintf(event_string + len, sizeof(event_string), "%s,", recovery);
+		len += scnprintf(event_string + len, sizeof(event_string) - len, "%s,", recovery);
 	}
 
 	if (recovery)
-- 
2.25.1