linux-kernel - [PATCH v2] drm/modes: Fix unterminated strncpy

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Date:   Wed, 31 Jul 2019 10:01:40 +0800
From:   Chuhong Yuan <hslester96@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Chuhong Yuan <hslester96@...il.com>
Subject: [PATCH v2] drm/modes: Fix unterminated strncpy

strncpy(dest, src, strlen(src)) leads to unterminated
dest, which is dangerous.
Fix it by using strscpy.

Signed-off-by: Chuhong Yuan <hslester96@...il.com>
---
Changes in v2:
  - Check whether mode_end + 1 exceeds
	the size of mode->name.

 drivers/gpu/drm/drm_modes.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index 80fcd5dc1558..b0369e690f36 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -1770,7 +1770,9 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
 	}
 
 	if (named_mode) {
-		strncpy(mode->name, name, mode_end);
+		if (mode_end + 1 > DRM_DISPLAY_MODE_LEN)
+			return false;
+		strscpy(mode->name, name, mode_end + 1);
 	} else {
 		ret = drm_mode_parse_cmdline_res_mode(name, mode_end,
 						      parse_extras,
-- 
2.20.1