[PATCH 1/1] s390/sclp: fix Secure-IPL facility detection

[PATCH 1/1] s390/sclp: fix Secure-IPL facility detection

[Alexander Egorenkov]

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@vger.kernel.org # 5.2+
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
---
 drivers/s390/char/sclp_early.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/char/sclp_early.c b/drivers/s390/char/sclp_early.c
index 2f3515fa242a..f3d5c7f4c13d 100644
--- a/drivers/s390/char/sclp_early.c
+++ b/drivers/s390/char/sclp_early.c
@@ -45,13 +45,14 @@ static void __init sclp_early_facilities_detect(void)
 	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;
-- 
2.31.1