Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, George Kennedy <george.kennedy@oracle.com>,
        syzbot+e5fd3e65515b48c02a30@syzkaller.appspotmail.com,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Dhaval Giani <dhaval.giani@oracle.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.8 605/633] fbmem: add margin check to fb_check_caps()
Date:   Tue, 27 Oct 2020 14:55:48 +0100
Message-Id: <20201027135551.195819272@linuxfoundation.org>
In-Reply-To: <20201027135522.655719020@linuxfoundation.org>
References: <20201027135522.655719020@linuxfoundation.org>
User-Agent: quilt/0.66
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: George Kennedy <george.kennedy@oracle.com>

[ Upstream commit a49145acfb975d921464b84fe00279f99827d816 ]

A fb_ioctl() FBIOPUT_VSCREENINFO call with invalid xres setting
or yres setting in struct fb_var_screeninfo will result in a
KASAN: vmalloc-out-of-bounds failure in bitfill_aligned() as
the margins are being cleared. The margins are cleared in
chunks and if the xres setting or yres setting is a value of
zero upto the chunk size, the failure will occur.

Add a margin check to validate xres and yres settings.

Signed-off-by: George Kennedy <george.kennedy@oracle.com>
Reported-by: syzbot+e5fd3e65515b48c02a30@syzkaller.appspotmail.com
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Dhaval Giani <dhaval.giani@oracle.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1594149963-13801-1-git-send-email-george.kennedy@oracle.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/video/fbdev/core/fbmem.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index da7c88ffaa6a8..1136b569ccb7c 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1006,6 +1006,10 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 		return 0;
 	}
 
+	/* bitfill_aligned() assumes that it's at least 8x8 */
+	if (var->xres < 8 || var->yres < 8)
+		return -EINVAL;
+
 	ret = info->fbops->fb_check_var(var, info);
 
 	if (ret)
-- 
2.25.1