linux-kernel - [tip:x86/urgent] x86/simplefb: Fix overflow causing bogus fall-back

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Message-ID: <tip-e33a29a5ae711162c6b6fefc0a2ef18f4a4254bf@git.kernel.org>
Date:	Thu, 3 Oct 2013 06:59:33 -0700
From:	tip-bot for Tom Gundersen <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, swarren@...dotorg.org, hpa@...or.com,
	mingo@...nel.org, swarren@...dia.com, geert@...ux-m68k.org,
	tglx@...utronix.de, teg@...m.no, dh.herrmann@...il.com
Subject: [tip:x86/urgent] x86/simplefb:
  Fix overflow causing bogus fall-back

Commit-ID:  e33a29a5ae711162c6b6fefc0a2ef18f4a4254bf
Gitweb:     http://git.kernel.org/tip/e33a29a5ae711162c6b6fefc0a2ef18f4a4254bf
Author:     Tom Gundersen <teg@...m.no>
AuthorDate: Tue, 1 Oct 2013 18:18:40 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 2 Oct 2013 07:50:40 +0200

x86/simplefb: Fix overflow causing bogus fall-back

On my MacBook Air lfb_size is 4M, which makes the bitshit
overflow (to 256GB - larger than 32 bits), meaning we fall
back to efifb unnecessarily.

Cast to u64 to avoid the overflow.

Signed-off-by: Tom Gundersen <teg@...m.no>
Reviewed-by: David Herrmann <dh.herrmann@...il.com>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Stephen Warren <swarren@...dia.com>
Cc: Stephen Warren <swarren@...dotorg.org>
Link: http://lkml.kernel.org/r/1380644320-1026-1-git-send-email-teg@jklm.no
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 22513e9..4ebd636 100644
--- a/arch/x86/kernel/sysfb_simplefb.c
+++ b/arch/x86/kernel/sysfb_simplefb.c
@@ -72,7 +72,7 @@ __init int create_simplefb(const struct screen_info *si,
 	 * the part that is occupied by the framebuffer */
 	len = mode->height * mode->stride;
 	len = PAGE_ALIGN(len);
-	if (len > si->lfb_size << 16) {
+	if (len > (u64)si->lfb_size << 16) {
 		printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
 		return -EINVAL;
 	}
--
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