linux-kernel - [PATCH AUTOSEL 6.13 19/31] s390/cio: Fix CHPID "configure" attribute caching

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

Message-Id: <20250218202455.3592096-19-sashal@kernel.org>
Date: Tue, 18 Feb 2025 15:24:39 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Peter Oberparleiter <oberpar@...ux.ibm.com>,
	Vineeth Vijayan <vneethv@...ux.ibm.com>,
	Eric Farman <farman@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Sasha Levin <sashal@...nel.org>,
	hca@...ux.ibm.com,
	agordeev@...ux.ibm.com,
	linux-s390@...r.kernel.org
Subject: [PATCH AUTOSEL 6.13 19/31] s390/cio: Fix CHPID "configure" attribute caching

From: Peter Oberparleiter <oberpar@...ux.ibm.com>

[ Upstream commit 32ae4a2992529e2c7934e422035fad1d9b0f1fb5 ]

In some environments, the SCLP firmware interface used to query a
CHPID's configured state is not supported. On these environments,
rapidly reading the corresponding sysfs attribute produces inconsistent
results:

  $ cat /sys/devices/css0/chp0.00/configure
  cat: /sys/devices/css0/chp0.00/configure: Operation not supported
  $ cat /sys/devices/css0/chp0.00/configure
  3

This occurs for example when Linux is run as a KVM guest. The
inconsistency is a result of CIO using cached results for generating
the value of the "configure" attribute while failing to handle the
situation where no data was returned by SCLP.

Fix this by not updating the cache-expiration timestamp when SCLP
returns no data. With the fix applied, the system response is
consistent:

  $ cat /sys/devices/css0/chp0.00/configure
  cat: /sys/devices/css0/chp0.00/configure: Operation not supported
  $ cat /sys/devices/css0/chp0.00/configure
  cat: /sys/devices/css0/chp0.00/configure: Operation not supported

Reviewed-by: Vineeth Vijayan <vneethv@...ux.ibm.com>
Reviewed-by: Eric Farman <farman@...ux.ibm.com>
Tested-by: Eric Farman <farman@...ux.ibm.com>
Signed-off-by: Peter Oberparleiter <oberpar@...ux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/s390/cio/chp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/cio/chp.c b/drivers/s390/cio/chp.c
index cba2d048a96b3..7855d88a49d85 100644
--- a/drivers/s390/cio/chp.c
+++ b/drivers/s390/cio/chp.c
@@ -695,7 +695,8 @@ static int info_update(void)
 	if (time_after(jiffies, chp_info_expires)) {
 		/* Data is too old, update. */
 		rc = sclp_chp_read_info(&chp_info);
-		chp_info_expires = jiffies + CHP_INFO_UPDATE_INTERVAL ;
+		if (!rc)
+			chp_info_expires = jiffies + CHP_INFO_UPDATE_INTERVAL;
 	}
 	mutex_unlock(&info_lock);
 
-- 
2.39.5