[PATCH v2 1/1] s390/zcrypt: Close speculative mem read possibility

[Harald Freudenberger <freude@linux.ibm.com>]

The domain value is extracted from a given CCA or EP11 ioctl struct
when a CPRB is about to be sent. Thus this is a user controlled value.
Under some special conditions (custom device node used, administrative
load) this value is used as an array index after bounds checking, but
without speculation barrier.

Add the missing array_index_nospec() call to prevent speculative
execution where this domain value is used.

Fixes: cfd68b33094e ("s390/zcrypt: Filter admin CPRBs on custom devices")
Reported-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Finn Callies <fcallies@linux.ibm.com>
Cc: stable@vger.kernel.org
---
 drivers/s390/crypto/zcrypt_api.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/s390/crypto/zcrypt_api.c b/drivers/s390/crypto/zcrypt_api.c
index f57189c2b839..593aace5fc48 100644
--- a/drivers/s390/crypto/zcrypt_api.c
+++ b/drivers/s390/crypto/zcrypt_api.c
@@ -879,6 +879,7 @@ static long _zcrypt_send_cprb(u32 xflags, struct ap_perms *perms,
 
 	if (perms != &ap_perms && domain < AP_DOMAINS) {
 		if (ap_msg.flags & AP_MSG_FLAG_ADMIN) {
+			domain = array_index_nospec(domain, AP_DOMAINS);
 			if (!test_bit_inv(domain, perms->adm)) {
 				rc = -ENODEV;
 				goto out;
@@ -1079,6 +1080,7 @@ static long _zcrypt_send_ep11_cprb(u32 xflags, struct ap_perms *perms,
 
 	if (perms != &ap_perms && domain < AUTOSEL_DOM) {
 		if (ap_msg.flags & AP_MSG_FLAG_ADMIN) {
+			domain = array_index_nospec(domain, AP_DOMAINS);
 			if (!test_bit_inv(domain, perms->adm)) {
 				rc = -ENODEV;
 				goto out;
-- 
2.43.0