linux-kernel - [Bugfix 2/2] x86/PCI/ACPI: Relax ACPI resource descriptor checks to work around BIOS bugs

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Date:	Wed,  4 Mar 2015 16:47:12 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Thomas Voegtle <tv@...96.de>, Hudd <hedede.l@...il.com>,
	Prakash Punnoor <prakash@...noor.de>,
	Francois Romieu <romieu@...zoreil.com>,
	Dave Airlie <airlied@...il.com>,
	Marcel Holtmann <marcel@...tmann.org>,
	Len Brown <lenb@...nel.org>
Cc:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Lv Zheng <lv.zheng@...el.com>
Subject: [Bugfix 2/2] x86/PCI/ACPI: Relax ACPI resource descriptor checks to work around BIOS bugs

Some BIOSes report incorrect length for ACPI address space descriptors,
so relax the checks to avoid regressions. This issue has appeared several
times as:
3162b6f0c5e1 ("PNPACPI: truncate _CRS windows with _LEN > _MAX - _MIN + 1")
d558b483d5a7 ("x86/PCI: truncate _CRS windows with _LEN > _MAX - _MIN + 1")
f238b414a74a ("PNPACPI: compute Address Space length rather than using _LEN")
48728e077480 ("x86/PCI: compute Address Space length rather than using _LEN")

Please refer to https://bugzilla.kernel.org/show_bug.cgi?id=94221
for more details and example malformed ACPI resource descriptors.

Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
Tested-by: Dave Airlie <airlied@...hat.com>
Tested-by: Prakash Punnoor <prakash@...noor.de>
---
 drivers/acpi/resource.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/resource.c b/drivers/acpi/resource.c
index c723668e3e27..5589a6e2a023 100644
--- a/drivers/acpi/resource.c
+++ b/drivers/acpi/resource.c
@@ -42,8 +42,10 @@ static bool acpi_dev_resource_len_valid(u64 start, u64 end, u64 len, bool io)
 	 * CHECKME: len might be required to check versus a minimum
 	 * length as well. 1 for io is fine, but for memory it does
 	 * not make any sense at all.
+	 * Note: some BIOSes report incorrect length for ACPI address space
+	 * descriptor, so remove check of 'reslen == len' to avoid regression.
 	 */
-	if (len && reslen && reslen == len && start <= end)
+	if (len && reslen && start <= end)
 		return true;
 
 	pr_debug("ACPI: invalid or unassigned resource %s [%016llx - %016llx] length [%016llx]\n",
-- 
1.7.10.4

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