linux-kernel - [PATCH 5.4 037/184] fbdev: zero-fill colormap in fbcmap.c

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Message-Id: <20210510101951.434751835@linuxfoundation.org>
Date:   Mon, 10 May 2021 12:18:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+47fa9c9c648b765305b9@...kaller.appspotmail.com,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Phillip Potter <phil@...lpotter.co.uk>
Subject: [PATCH 5.4 037/184] fbdev: zero-fill colormap in fbcmap.c

From: Phillip Potter <phil@...lpotter.co.uk>

commit 19ab233989d0f7ab1de19a036e247afa4a0a1e9c upstream.

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@...kaller.appspotmail.com
Cc: stable <stable@...r.kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
Signed-off-by: Phillip Potter <phil@...lpotter.co.uk>
Link: https://lore.kernel.org/r/20210331220719.1499743-1-phil@philpotter.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/video/fbdev/core/fbcmap.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- 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 *cm
 		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 {