[PATCH] zero-fill colormap in drivers/video/fbdev/core/fbcmap.c

Use kzalloc() rather than kmalloc() for the dynamically allocated parts
of the colormap in fb_alloc_cmap_gfp, to prevent a leak of random kernel
data to userspace under certain circumstances.

Fixes a KMSAN-found infoleak bug reported by syzbot at:
https://syzkaller.appspot.com/bug?id=741578659feabd108ad9e06696f0c1f2e69c4b6e

Reported-by: syzbot+47fa9c9c648b765305b9@syzkaller.appspotmail.com
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
---
 drivers/video/fbdev/core/fbcmap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/video/fbdev/core/fbcmap.c b/drivers/video/fbdev/core/fbcmap.c
index 757d5c3f620b..ff09e57f3c38 100644
--- a/drivers/video/fbdev/core/fbcmap.c
+++ b/drivers/video/fbdev/core/fbcmap.c

@@ -101,17 +101,17 @@ int fb_alloc_cmap_gfp(struct fb_cmap *cmap, int len, int transp, gfp_t flags)
 		if (!len)
 			return 0;
 
-		cmap->red = kmalloc(size, flags);
+		cmap->red = kzalloc(size, flags);
 		if (!cmap->red)
 			goto fail;
-		cmap->green = kmalloc(size, flags);
+		cmap->green = kzalloc(size, flags);
 		if (!cmap->green)
 			goto fail;
-		cmap->blue = kmalloc(size, flags);
+		cmap->blue = kzalloc(size, flags);
 		if (!cmap->blue)
 			goto fail;
 		if (transp) {
-			cmap->transp = kmalloc(size, flags);
+			cmap->transp = kzalloc(size, flags);
 			if (!cmap->transp)
 				goto fail;
 		} else {

-- 
2.30.2

On Thu, Apr 1, 2021 at 12:09 AM Phillip Potter [off-list ref] wrote:

Use kzalloc() rather than kmalloc() for the dynamically allocated parts
of the colormap in fb_alloc_cmap_gfp, to prevent a leak of random kernel
data to userspace under certain circumstances.

Fixes a KMSAN-found infoleak bug reported by syzbot at:
https://syzkaller.appspot.com/bug?id=741578659feabd108ad9e06696f0c1f2e69c4b6e

Reported-by: syzbot+47fa9c9c648b765305b9@syzkaller.appspotmail.com
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

On Thu, Apr 01, 2021 at 11:55:50AM +0200, Geert Uytterhoeven wrote:

On Thu, Apr 1, 2021 at 12:09 AM Phillip Potter [off-list ref] wrote:

quoted

Use kzalloc() rather than kmalloc() for the dynamically allocated parts
of the colormap in fb_alloc_cmap_gfp, to prevent a leak of random kernel
data to userspace under certain circumstances.

Fixes a KMSAN-found infoleak bug reported by syzbot at:
https://syzkaller.appspot.com/bug?id=741578659feabd108ad9e06696f0c1f2e69c4b6e

Reported-by: syzbot+47fa9c9c648b765305b9@syzkaller.appspotmail.com
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Dear Geert

Thank you for your review :-)

Regards,
Phil

On Wed, Mar 31, 2021 at 11:07:19PM +0100, Phillip Potter wrote:

Use kzalloc() rather than kmalloc() for the dynamically allocated parts
of the colormap in fb_alloc_cmap_gfp, to prevent a leak of random kernel
data to userspace under certain circumstances.

Fixes a KMSAN-found infoleak bug reported by syzbot at:
https://syzkaller.appspot.com/bug?id=741578659feabd108ad9e06696f0c1f2e69c4b6e

Reported-by: syzbot+47fa9c9c648b765305b9@syzkaller.appspotmail.com
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
---
 drivers/video/fbdev/core/fbcmap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Daniel, want me to take this?

thanks,

greg k-h