On Wed, Mar 20, 2024 at 11:48:52PM +0100, Helge Deller wrote: > On 3/20/24 23:35, Justin Stitt wrote: > > Hi, > > > > On Wed, Mar 20, 2024 at 12:56 AM Helge Deller <deller@xxxxxx> wrote: > > > > > > On 3/19/24 00:46, Justin Stitt wrote: > > > > 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@xxxxxxxxxxxxxxx > > > > Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx> > > > > --- > > > > 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"); > > > > > > I wonder if you really build-tested this, as this driver is for the mips architecture... > > > And I don't see a strscpy() function which takes just 2 arguments. > > > But I might be wrong.... > > > > I did build successfully :thumbs_up: > > > > Commit e6584c3964f2f ("string: Allow 2-argument strscpy()") introduced > > this new strscpy() form; it is present in string.h on Linus' tree. > > Interesting patch. > Might give compile problems if patches like yours gets automatically > picked up to stable series as long as Kees patch hasn't been backported yet... > Anyway, thanks for the pointer! > I'll apply your patch in the next round for fbdev. Hi! I haven't seen this show up in -next yet. Have you had a chance to pick it up? There are also these too: https://lore.kernel.org/all/20240320-strncpy-drivers-video-fbdev-fsl-diu-fb-c-v1-1-3cd3c012fa8c@xxxxxxxxxx/ https://patchwork.kernel.org/project/linux-hardening/patch/20240320-strncpy-drivers-video-fbdev-uvesafb-c-v1-1-fd6af3766c80@xxxxxxxxxx/ https://patchwork.kernel.org/project/linux-hardening/patch/20240320-strncpy-drivers-video-hdmi-c-v1-1-f9a08168cdaf@xxxxxxxxxx/ I can toss all of these into the hardening tree if that makes it easier for you? Thanks! -Kees -- Kees Cook
