linux-kernel - [PATCH 5.4 207/260] s390/sclp: fix Secure-IPL facility detection

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Message-Id: <20210920163938.142246010@linuxfoundation.org>
Date:   Mon, 20 Sep 2021 18:43:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Alexander Egorenkov <egorenar@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Subject: [PATCH 5.4 207/260] s390/sclp: fix Secure-IPL facility detection

From: Alexander Egorenkov <egorenar@...ux.ibm.com>

commit d76b14f3971a0638b6cd0da289f8b48acee287d0 upstream.

Prevent out-of-range access if the returned SCLP SCCB response is smaller
in size than the address of the Secure-IPL flag.

Fixes: c9896acc7851 ("s390/ipl: Provide has_secure sysfs attribute")
Cc: stable@...r.kernel.org # 5.2+
Signed-off-by: Alexander Egorenkov <egorenar@...ux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/s390/char/sclp_early.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/s390/char/sclp_early.c
+++ b/drivers/s390/char/sclp_early.c
@@ -40,13 +40,14 @@ static void __init sclp_early_facilities
 	sclp.has_gisaf = !!(sccb->fac118 & 0x08);
 	sclp.has_hvs = !!(sccb->fac119 & 0x80);
 	sclp.has_kss = !!(sccb->fac98 & 0x01);
-	sclp.has_sipl = !!(sccb->cbl & 0x4000);
 	if (sccb->fac85 & 0x02)
 		S390_lowcore.machine_flags |= MACHINE_FLAG_ESOP;
 	if (sccb->fac91 & 0x40)
 		S390_lowcore.machine_flags |= MACHINE_FLAG_TLB_GUEST;
 	if (sccb->cpuoff > 134)
 		sclp.has_diag318 = !!(sccb->byte_134 & 0x80);
+	if (sccb->cpuoff > 137)
+		sclp.has_sipl = !!(sccb->cbl & 0x4000);
 	sclp.rnmax = sccb->rnmax ? sccb->rnmax : sccb->rnmax2;
 	sclp.rzm = sccb->rnsize ? sccb->rnsize : sccb->rnsize2;
 	sclp.rzm <<= 20;