linux-kernel - [PATCH] rtc: efi: Fail probing if RTC reads don't work

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1465119356-129799-1-git-send-email-agraf@suse.de>
Date:	Sun,  5 Jun 2016 11:35:56 +0200
From:	Alexander Graf <agraf@...e.de>
To:	rtc-linux@...glegroups.com
Cc:	leif.lindholm@...aro.org, linux-kernel@...r.kernel.org,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH] rtc: efi: Fail probing if RTC reads don't work

While the EFI spec mandates an RTC, not every implementation actually adheres
to that rule (or can adhere to it - some systems just don't have an RTC).

For those, we really don't want to probe the EFI RTC driver at all, because if
we do we'd get a non-functional driver that does nothing useful but only spills
our kernel log with warnings.

Signed-off-by: Alexander Graf <agraf@...e.de>
---
 drivers/rtc/rtc-efi.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/rtc/rtc-efi.c b/drivers/rtc/rtc-efi.c
index 96d3860..0130afd 100644
--- a/drivers/rtc/rtc-efi.c
+++ b/drivers/rtc/rtc-efi.c
@@ -259,6 +259,12 @@ static const struct rtc_class_ops efi_rtc_ops = {
 static int __init efi_rtc_probe(struct platform_device *dev)
 {
 	struct rtc_device *rtc;
+	efi_time_t eft;
+	efi_time_cap_t cap;
+
+	/* First check if the RTC is usable */
+	if (efi.get_time(&eft, &cap) != EFI_SUCCESS)
+		return -ENODEV;
 
 	rtc = devm_rtc_device_register(&dev->dev, "rtc-efi", &efi_rtc_ops,
 					THIS_MODULE);
-- 
1.8.5.6