[PATCH 7.1 342/438] s390/zcrypt: Close speculative mem read possibility

7.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Harald Freudenberger <[email protected]>

commit e935cd525af4c6ed2e2c6404aa27ca19c7f39ddb upstream.

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")
Cc: [email protected]
Reported-by: Christian Borntraeger <[email protected]>
Reviewed-by: Finn Callies <[email protected]>
Signed-off-by: Harald Freudenberger <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 drivers/s390/crypto/zcrypt_api.c |    2 ++
 1 file changed, 2 insertions(+)

--- 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
 
 	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 x
 
 	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;