s390/zcrypt: add copy_from_user length plausibility checks

There have been identified some places in the zcrypt
device driver where copy_from_user() is called but the
length value is not explicitly checked.

So now some plausibility checks and comments have been
introduced there.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/drivers/s390/crypto/zcrypt_cca_key.h b/drivers/s390/crypto/zcrypt_cca_key.h
index 011d61d..1752622 100644 (file)
--- a/drivers/s390/crypto/zcrypt_cca_key.h
+++ b/drivers/s390/crypto/zcrypt_cca_key.h
@@ -99,7 +99,7 @@ struct cca_pvt_ext_CRT_sec {
  * @mex: pointer to user input data
  * @p: pointer to memory area for the key
  *
- * Returns the size of the key area or -EFAULT
+ * Returns the size of the key area or negative errno value.
  */
 static inline int zcrypt_type6_mex_key_en(struct ica_rsa_modexpo *mex, void *p)
 {
@@ -118,6 +118,15 @@ static inline int zcrypt_type6_mex_key_en(struct ica_rsa_modexpo *mex, void *p)
        unsigned char *temp;
        int i;
 
+       /*
+        * The inputdatalength was a selection criteria in the dispatching
+        * function zcrypt_rsa_modexpo(). However, do a plausibility check
+        * here to make sure the following copy_from_user() can't be utilized
+        * to compromise the system.
+        */
+       if (WARN_ON_ONCE(mex->inputdatalength > 512))
+               return -EINVAL;
+
        memset(key, 0, sizeof(*key));
 
        key->pubHdr = static_pub_hdr;
@@ -178,6 +187,15 @@ static inline int zcrypt_type6_crt_key(struct ica_rsa_modexpo_crt *crt, void *p)
        struct cca_public_sec *pub;
        int short_len, long_len, pad_len, key_len, size;
 
+       /*
+        * The inputdatalength was a selection criteria in the dispatching
+        * function zcrypt_rsa_crt(). However, do a plausibility check
+        * here to make sure the following copy_from_user() can't be utilized
+        * to compromise the system.
+        */
+       if (WARN_ON_ONCE(crt->inputdatalength > 512))
+               return -EINVAL;
+
        memset(key, 0, sizeof(*key));
 
        short_len = (crt->inputdatalength + 1) / 2;

diff --git a/drivers/s390/crypto/zcrypt_msgtype6.c b/drivers/s390/crypto/zcrypt_msgtype6.c
index 97d4bac..e70ae07 100644 (file)
--- a/drivers/s390/crypto/zcrypt_msgtype6.c
+++ b/drivers/s390/crypto/zcrypt_msgtype6.c
@@ -246,7 +246,7 @@ int speed_idx_ep11(int req_type)
  * @ap_msg: pointer to AP message
  * @mex: pointer to user input data
  *
- * Returns 0 on success or -EFAULT.
+ * Returns 0 on success or negative errno value.
  */
 static int ICAMEX_msg_to_type6MEX_msgX(struct zcrypt_queue *zq,
                                       struct ap_message *ap_msg,
@@ -272,6 +272,14 @@ static int ICAMEX_msg_to_type6MEX_msgX(struct zcrypt_queue *zq,
        } __packed * msg = ap_msg->message;
        int size;
 
+       /*
+        * The inputdatalength was a selection criteria in the dispatching
+        * function zcrypt_rsa_modexpo(). However, make sure the following
+        * copy_from_user() never exceeds the allocated buffer space.
+        */
+       if (WARN_ON_ONCE(mex->inputdatalength > PAGE_SIZE))
+               return -EINVAL;
+
        /* VUD.ciphertext */
        msg->length = mex->inputdatalength + 2;
        if (copy_from_user(msg->text, mex->inputdata, mex->inputdatalength))
@@ -307,7 +315,7 @@ static int ICAMEX_msg_to_type6MEX_msgX(struct zcrypt_queue *zq,
  * @ap_msg: pointer to AP message
  * @crt: pointer to user input data
  *
- * Returns 0 on success or -EFAULT.
+ * Returns 0 on success or negative errno value.
  */
 static int ICACRT_msg_to_type6CRT_msgX(struct zcrypt_queue *zq,
                                       struct ap_message *ap_msg,
@@ -334,6 +342,14 @@ static int ICACRT_msg_to_type6CRT_msgX(struct zcrypt_queue *zq,
        } __packed * msg = ap_msg->message;
        int size;
 
+       /*
+        * The inputdatalength was a selection criteria in the dispatching
+        * function zcrypt_rsa_crt(). However, make sure the following
+        * copy_from_user() never exceeds the allocated buffer space.
+        */
+       if (WARN_ON_ONCE(crt->inputdatalength > PAGE_SIZE))
+               return -EINVAL;
+
        /* VUD.ciphertext */
        msg->length = crt->inputdatalength + 2;
        if (copy_from_user(msg->text, crt->inputdata, crt->inputdatalength))