[PATCH] x86/sysfb: Fix check for bad VRAM size

From: Arvind Sankar <nivedita@alum.mit.edu>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	Christopher Head <bugs@chead.ca>
Subject: [PATCH] x86/sysfb: Fix check for bad VRAM size
Date: Tue,  7 Jan 2020 18:04:10 -0500	[thread overview]
Message-ID: <20200107230410.2291947-1-nivedita@alum.mit.edu> (raw)

When checking whether the reported lfb_size makes sense, we PAGE_ALIGN
height * stride before seeing whether it exceeds the reported size.

This doesn't work if height * stride is not an exact number of pages.
For example, as reported in kernel bugzilla linked, an 800x600x32 EFI
framebuffer gets skipped because of this.

Move the PAGE_ALIGN to after the check vs size.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206051
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
 arch/x86/kernel/sysfb_simplefb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/sysfb_simplefb.c b/arch/x86/kernel/sysfb_simplefb.c
index 01f0e2263b86..298fc1edd9c9 100644
--- a/arch/x86/kernel/sysfb_simplefb.c
+++ b/arch/x86/kernel/sysfb_simplefb.c
@@ -90,11 +90,11 @@ __init int create_simplefb(const struct screen_info *si,
 	if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
 		size <<= 16;
 	length = mode->height * mode->stride;
-	length = PAGE_ALIGN(length);
 	if (length > size) {
 		printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
 		return -EINVAL;
 	}
+	length = PAGE_ALIGN(length);
 
 	/* setup IORESOURCE_MEM as framebuffer memory */
 	memset(&res, 0, sizeof(res));
-- 
2.24.1

