KEYS: Add an iovec version of KEYCTL_INSTANTIATE

Add a keyctl op (KEYCTL_INSTANTIATE_IOV) that is like KEYCTL_INSTANTIATE, but
takes an iovec array and concatenates the data in-kernel into one buffer.
Since the KEYCTL_INSTANTIATE copies the data anyway, this isn't too much of a
problem.

Signed-off-by: David Howells <[e-mail]>
Signed-off-by: James Morris <[e-mail]>

Documentation/keys.txt

···
 	long keyctl(KEYCTL_INSTANTIATE, key_serial_t key,
 		    const void *payload, size_t plen,
 		    key_serial_t keyring);
+	long keyctl(KEYCTL_INSTANTIATE_IOV, key_serial_t key,
+		    const struct iovec *payload_iov, unsigned ioc,
+		    key_serial_t keyring);
 
      If the kernel calls back to userspace to complete the instantiation of a
      key, userspace should use this call to supply data for the key before the
···
      this case too.
 
      The payload and plen arguments describe the payload data as for add_key().
+
+     The payload_iov and ioc arguments describe the payload data in an iovec
+     array instead of a single buffer.
 
 
  (*) Negatively instantiate a partially constructed key.
···
 example, the KDE desktop manager).
 
 The program (or whatever it calls) should finish construction of the key by
-calling KEYCTL_INSTANTIATE, which also permits it to cache the key in one of
-the keyrings (probably the session ring) before returning. Alternatively, the
-key can be marked as negative with KEYCTL_NEGATE or KEYCTL_REJECT; this also
-permits the key to be cached in one of the keyrings.
+calling KEYCTL_INSTANTIATE or KEYCTL_INSTANTIATE_IOV, which also permits it to
+cache the key in one of the keyrings (probably the session ring) before
+returning.  Alternatively, the key can be marked as negative with KEYCTL_NEGATE
+or KEYCTL_REJECT; this also permits the key to be cached in one of the
+keyrings.
 
 If it returns with the key remaining in the unconstructed state, the key will
 be marked as being negative, it will be added to the session keyring, and an

arch/x86/Kconfig

···
 	def_bool y
 	depends on COMPAT && SYSVIPC
 
+config KEYS_COMPAT
+	bool
+	depends on COMPAT && KEYS
+	default y
+
 endmenu
 
 

include/linux/keyctl.h

···
 #define KEYCTL_GET_SECURITY		17	/* get key security label */
 #define KEYCTL_SESSION_TO_PARENT	18	/* apply session keyring to parent process */
 #define KEYCTL_REJECT			19	/* reject a partially constructed key */
+#define KEYCTL_INSTANTIATE_IOV		20	/* instantiate a partially constructed key */
 
 #endif /*  _LINUX_KEYCTL_H */

security/keys/compat.c

···
 #include <linux/syscalls.h>
 #include <linux/keyctl.h>
 #include <linux/compat.h>
+#include <linux/slab.h>
 #include "internal.h"
+
+/*
+ * Instantiate a key with the specified compatibility multipart payload and
+ * link the key into the destination keyring if one is given.
+ *
+ * The caller must have the appropriate instantiation permit set for this to
+ * work (see keyctl_assume_authority).  No other permissions are required.
+ *
+ * If successful, 0 will be returned.
+ */
+long compat_keyctl_instantiate_key_iov(
+	key_serial_t id,
+	const struct compat_iovec __user *_payload_iov,
+	unsigned ioc,
+	key_serial_t ringid)
+{
+	struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
+	long ret;
+
+	if (_payload_iov == 0 || ioc == 0)
+		goto no_payload;
+
+	ret = compat_rw_copy_check_uvector(WRITE, _payload_iov, ioc,
+					   ARRAY_SIZE(iovstack),
+					   iovstack, &iov);
+	if (ret < 0)
+		return ret;
+	if (ret == 0)
+		goto no_payload_free;
+
+	ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid);
+
+	if (iov != iovstack)
+		kfree(iov);
+	return ret;
+
+no_payload_free:
+	if (iov != iovstack)
+		kfree(iov);
+no_payload:
+	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
+}
 
 /*
  * The key control system call, 32-bit compatibility version for 64-bit archs
···
 
 	case KEYCTL_REJECT:
 		return keyctl_reject_key(arg2, arg3, arg4, arg5);
+
+	case KEYCTL_INSTANTIATE_IOV:
+		return compat_keyctl_instantiate_key_iov(
+			arg2, compat_ptr(arg3), arg4, arg5);
 
 	default:
 		return -EOPNOTSUPP;

security/keys/internal.h

···
 				size_t buflen);
 extern long keyctl_session_to_parent(void);
 extern long keyctl_reject_key(key_serial_t, unsigned, unsigned, key_serial_t);
+extern long keyctl_instantiate_key_iov(key_serial_t,
+				       const struct iovec __user *,
+				       unsigned, key_serial_t);
+
+extern long keyctl_instantiate_key_common(key_serial_t,
+					  const struct iovec __user *,
+					  unsigned, size_t, key_serial_t);
 
 /*
  * Debugging key validation

security/keys/keyctl.c

···
 }
 
 /*
+ * Copy the iovec data from userspace
+ */
+static long copy_from_user_iovec(void *buffer, const struct iovec *iov,
+				 unsigned ioc)
+{
+	for (; ioc > 0; ioc--) {
+		if (copy_from_user(buffer, iov->iov_base, iov->iov_len) != 0)
+			return -EFAULT;
+		buffer += iov->iov_len;
+		iov++;
+	}
+	return 0;
+}
+
+/*
  * Instantiate a key with the specified payload and link the key into the
  * destination keyring if one is given.
  *
···
  *
  * If successful, 0 will be returned.
  */
-long keyctl_instantiate_key(key_serial_t id,
-			    const void __user *_payload,
-			    size_t plen,
-			    key_serial_t ringid)
+long keyctl_instantiate_key_common(key_serial_t id,
+				   const struct iovec *payload_iov,
+				   unsigned ioc,
+				   size_t plen,
+				   key_serial_t ringid)
 {
 	const struct cred *cred = current_cred();
 	struct request_key_auth *rka;
···
 	/* pull the payload in if one was supplied */
 	payload = NULL;
 
-	if (_payload) {
+	if (payload_iov) {
 		ret = -ENOMEM;
 		payload = kmalloc(plen, GFP_KERNEL);
 		if (!payload) {
···
 				goto error;
 		}
 
-		ret = -EFAULT;
-		if (copy_from_user(payload, _payload, plen) != 0)
+		ret = copy_from_user_iovec(payload, payload_iov, ioc);
+		if (ret < 0)
 			goto error2;
 	}
 
···
 		vfree(payload);
 error:
 	return ret;
+}
+
+/*
+ * Instantiate a key with the specified payload and link the key into the
+ * destination keyring if one is given.
+ *
+ * The caller must have the appropriate instantiation permit set for this to
+ * work (see keyctl_assume_authority).  No other permissions are required.
+ *
+ * If successful, 0 will be returned.
+ */
+long keyctl_instantiate_key(key_serial_t id,
+			    const void __user *_payload,
+			    size_t plen,
+			    key_serial_t ringid)
+{
+	if (_payload && plen) {
+		struct iovec iov[1] = {
+			[0].iov_base = (void __user *)_payload,
+			[0].iov_len  = plen
+		};
+
+		return keyctl_instantiate_key_common(id, iov, 1, plen, ringid);
+	}
+
+	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
+}
+
+/*
+ * Instantiate a key with the specified multipart payload and link the key into
+ * the destination keyring if one is given.
+ *
+ * The caller must have the appropriate instantiation permit set for this to
+ * work (see keyctl_assume_authority).  No other permissions are required.
+ *
+ * If successful, 0 will be returned.
+ */
+long keyctl_instantiate_key_iov(key_serial_t id,
+				const struct iovec __user *_payload_iov,
+				unsigned ioc,
+				key_serial_t ringid)
+{
+	struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
+	long ret;
+
+	if (_payload_iov == 0 || ioc == 0)
+		goto no_payload;
+
+	ret = rw_copy_check_uvector(WRITE, _payload_iov, ioc,
+				    ARRAY_SIZE(iovstack), iovstack, &iov);
+	if (ret < 0)
+		return ret;
+	if (ret == 0)
+		goto no_payload_free;
+
+	ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid);
+
+	if (iov != iovstack)
+		kfree(iov);
+	return ret;
+
+no_payload_free:
+	if (iov != iovstack)
+		kfree(iov);
+no_payload:
+	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
 }
 
 /*
···
 					 (unsigned) arg3,
 					 (unsigned) arg4,
 					 (key_serial_t) arg5);
+
+	case KEYCTL_INSTANTIATE_IOV:
+		return keyctl_instantiate_key_iov(
+			(key_serial_t) arg2,
+			(const struct iovec __user *) arg3,
+			(unsigned) arg4,
+			(key_serial_t) arg5);
 
 	default:
 		return -EOPNOTSUPP;