fbdev: zero-fill colormap in 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
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20210331220719.1499743-1-phil@philpotter.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/video/fbdev/core/fbcmap.c b/drivers/video/fbdev/core/fbcmap.c
index 757d5c3..ff09e57 100644 (file)
--- 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 {