kernel: Use BStackOrHeapArray in fd & port vector I/O syscalls.

The socket syscall needs to still use the heap. Also add a comment
around get_iovecs_from_user() indicating what callers must do.

headers/private/kernel/util/iovec_support.h

@@ -41,36 +41,31 @@ generic_memcpy(generic_addr_t dest, bool destPhysical, generic_addr_t src, bool
 
 #ifdef IS_USER_ADDRESS
 
+/*!
+ * Copies an array of `iovec`s from userland.
+ * Callers must verify vecCount <= IOV_MAX and supply their own vecs buffer.
+ */
 static inline status_t
-get_iovecs_from_user(const iovec* userVecs, size_t vecCount, iovec*& vecs,
+get_iovecs_from_user(const iovec* userVecs, size_t vecCount, iovec* vecs,
 	bool permitNull = false)
 {
-	// prevent integer overflow
-	if (vecCount > IOV_MAX || vecCount == 0)
+	if (vecCount == 0)
 		return B_BAD_VALUE;
 
 	if (!IS_USER_ADDRESS(userVecs))
 		return B_BAD_ADDRESS;
 
-	vecs = (iovec*)malloc(sizeof(iovec) * vecCount);
-	if (vecs == NULL)
-		return B_NO_MEMORY;
-
-	if (user_memcpy(vecs, userVecs, sizeof(iovec) * vecCount) != B_OK) {
-		free(vecs);
+	if (user_memcpy(vecs, userVecs, sizeof(iovec) * vecCount) != B_OK)
 		return B_BAD_ADDRESS;
-	}
 
 	size_t total = 0;
 	for (size_t i = 0; i < vecCount; i++) {
 		if (permitNull && vecs[i].iov_base == NULL)
 			continue;
 		if (!is_user_address_range(vecs[i].iov_base, vecs[i].iov_len)) {
-			free(vecs);
 			return B_BAD_ADDRESS;
 		}
 		if (vecs[i].iov_len > SSIZE_MAX || total > (SSIZE_MAX - vecs[i].iov_len)) {
-			free(vecs);
 			return B_BAD_VALUE;
 		}
 		total += vecs[i].iov_len;

src/system/kernel/fs/fd.cpp

@@ -19,6 +19,7 @@
 #include <AutoDeleter.h>
 #include <AutoDeleterDrivers.h>
 #include <BytePointer.h>
+#include <StackOrHeapArray.h>
 
 #include <syscalls.h>
 #include <syscall_restart.h>
@@ -759,12 +760,16 @@ common_user_vector_io(int fd, off_t pos, const iovec* userVecs, size_t count,
 {
 	if (pos < -1)
 		return B_BAD_VALUE;
+	if (count > IOV_MAX)
+		return B_BAD_VALUE;
+
+	BStackOrHeapArray<iovec, 16> vecs(count);
+	if (!vecs.IsValid())
+		return B_NO_MEMORY;
 
-	iovec* vecs;
 	status_t error = get_iovecs_from_user(userVecs, count, vecs, true);
 	if (error != B_OK)
 		return error;
-	MemoryDeleter _(vecs);
 
 	FileDescriptorPutter descriptor(get_fd(get_current_io_context(false), fd));
 	if (!descriptor.IsSet())

src/system/kernel/fs/socket.cpp

@@ -164,11 +164,14 @@ prepare_userland_msghdr(const msghdr* userMessage, msghdr& message,
 	if (message.msg_iovlen < 0 || message.msg_iovlen > IOV_MAX)
 		return EMSGSIZE;
 	if (userVecs != NULL && message.msg_iovlen > 0) {
-		iovec* vecs;
+		iovec* vecs = (iovec*)malloc(sizeof(iovec) * message.msg_iovlen);
+		if (vecs == NULL)
+			return B_NO_MEMORY;
+		vecsDeleter.SetTo(vecs);
+
 		status_t error = get_iovecs_from_user(message.msg_iov, message.msg_iovlen, vecs);
 		if (error != B_OK)
 			return error;
-		vecsDeleter.SetTo(vecs);
 		message.msg_iov = vecs;
 	} else {
 		message.msg_iov = NULL;

src/system/kernel/port.cpp

@@ -22,6 +22,7 @@
 #include <OS.h>
 
 #include <AutoDeleter.h>
+#include <StackOrHeapArray.h>
 
 #include <arch/int.h>
 #include <heap.h>
@@ -1920,10 +1921,13 @@ _user_writev_port_etc(port_id port, int32 messageCode, const iovec *userVecs,
 
 	if (userVecs == NULL && bufferSize != 0)
 		return B_BAD_VALUE;
-	if (userVecs != NULL && !IS_USER_ADDRESS(userVecs))
-		return B_BAD_ADDRESS;
+	if (vecCount > IOV_MAX)
+		return B_BAD_VALUE;
+
+	BStackOrHeapArray<iovec, 16> vecs(vecCount);
+	if (!vecs.IsValid())
+		return B_NO_MEMORY;
 
-	iovec *vecs = NULL;
 	if (userVecs != NULL && vecCount != 0) {
 		status_t status = get_iovecs_from_user(userVecs, vecCount, vecs);
 		if (status != B_OK)
@@ -1934,7 +1938,6 @@ _user_writev_port_etc(port_id port, int32 messageCode, const iovec *userVecs,
 		bufferSize, flags | PORT_FLAG_USE_USER_MEMCPY | B_CAN_INTERRUPT,
 		timeout);
 
-	free(vecs);
 	return syscall_restart_handle_timeout_post(status, timeout);
 }