linux-hardening - [PATCH] video: fbdev: au1200fb: replace deprecated strncpy with strscpy

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Message-ID: <20240318-strncpy-drivers-video-fbdev-au1200fb-c-v1-1-680802a9f10a@google.com>
Date: Mon, 18 Mar 2024 23:46:33 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Helge Deller <deller@....de>
Cc: linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] video: fbdev: au1200fb: replace deprecated strncpy with strscpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

Let's use the new 2-argument strscpy() which guarantees NUL-termination
on the destination buffer while also simplifying the syntax. Note that
strscpy() will not NUL-pad the destination buffer like strncpy() does.

However, the NUL-padding behavior of strncpy() is not required since
fbdev is already NUL-allocated from au1200fb_drv_probe() ->
frameuffer_alloc(), rendering any additional NUL-padding redundant.
|	p = kzalloc(fb_info_size + size, GFP_KERNEL);

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/video/fbdev/au1200fb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/au1200fb.c b/drivers/video/fbdev/au1200fb.c
index 6f20efc663d7..e718fea63662 100644
--- a/drivers/video/fbdev/au1200fb.c
+++ b/drivers/video/fbdev/au1200fb.c
@@ -1557,7 +1557,7 @@ static int au1200fb_init_fbinfo(struct au1200fb_device *fbdev)
 		return ret;
 	}
 
-	strncpy(fbi->fix.id, "AU1200", sizeof(fbi->fix.id));
+	strscpy(fbi->fix.id, "AU1200");
 	fbi->fix.smem_start = fbdev->fb_phys;
 	fbi->fix.smem_len = fbdev->fb_len;
 	fbi->fix.type = FB_TYPE_PACKED_PIXELS;

---
base-commit: bf3a69c6861ff4dc7892d895c87074af7bc1c400
change-id: 20240318-strncpy-drivers-video-fbdev-au1200fb-c-7bc337998096

Best regards,
--
Justin Stitt <justinstitt@...gle.com>