linux-kernel - [PATCH 2/3] x86/sysfb_efi: Fix valid BAR address range check

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Message-Id: <1462303781-8686-3-git-send-email-matt@codeblueprint.co.uk>
Date:	Tue,  3 May 2016 20:29:40 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H . Peter Anvin" <hpa@...or.com>
Cc:	Wang YanQing <udknight@...il.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	Matt Fleming <matt@...eblueprint.co.uk>,
	David Herrmann <dh.herrmann@...il.com>,
	Peter Jones <pjones@...hat.com>, stable@...r.kernel.org,
	Tomi Valkeinen <tomi.valkeinen@...com>
Subject: [PATCH 2/3] x86/sysfb_efi: Fix valid BAR address range check

From: Wang YanQing <udknight@...il.com>

We can't just break out when meet start is equal to zero,
this will cause us to miss valid address ranges in later BARs.

On the other hand, it isn't enough to test start only
for below situation:

  0(start) <= lfb_base < end

Due to the BUG this patch fix, I can't use video=efifb:
boot parameter to get efifb on my new ThinkPad E550 for
my old linux system hard disk with 3.10 kernel. In 3.10,
efifb is the only choice due to DRM/I915 in it doesn't
support the GPU.

This patch also add a trivial optimization, break out
after we find the address range is valid without test
later BARs.

Signed-off-by: Wang YanQing <udknight@...il.com>
Reviewed-by: Peter Jones <pjones@...hat.com>
Cc: David Herrmann <dh.herrmann@...il.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Tomi Valkeinen <tomi.valkeinen@...com>
Cc: <stable@...r.kernel.org>
[ Updated changelog ]
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
---
 arch/x86/kernel/sysfb_efi.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/sysfb_efi.c b/arch/x86/kernel/sysfb_efi.c
index b285d4e8c68e..5da924bbf0a0 100644
--- a/arch/x86/kernel/sysfb_efi.c
+++ b/arch/x86/kernel/sysfb_efi.c
@@ -106,14 +106,24 @@ static int __init efifb_set_system(const struct dmi_system_id *id)
 					continue;
 				for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
 					resource_size_t start, end;
+					unsigned long flags;
+
+					flags = pci_resource_flags(dev, i);
+					if (!(flags & IORESOURCE_MEM))
+						continue;
+
+					if (flags & IORESOURCE_UNSET)
+						continue;
+
+					if (pci_resource_len(dev, i) == 0)
+						continue;
 
 					start = pci_resource_start(dev, i);
-					if (start == 0)
-						break;
 					end = pci_resource_end(dev, i);
 					if (screen_info.lfb_base >= start &&
 					    screen_info.lfb_base < end) {
 						found_bar = 1;
+						break;
 					}
 				}
 			}
-- 
2.7.3