Kernel: Make sys$recvfrom() with MSG_DONTWAIT not so racy

Instead of temporary changing the open file description's "blocking"
flag while doing a non-waiting recvfrom, we instead plumb the currently
wanted blocking behavior all the way through to the underlying socket.

1 files changed, 2 insertions, 7 deletions

diff --git a/Kernel/Syscalls/socket.cpp b/Kernel/Syscalls/socket.cpp
index 70eded6dc4..d7e292011f 100644
--- a/Kernel/Syscalls/socket.cpp
+++ b/Kernel/Syscalls/socket.cpp
@@ -241,15 +241,10 @@ ErrorOr<FlatPtr> Process::sys$recvmsg(int sockfd, Userspace<struct msghdr*> user
     if (socket.is_shut_down_for_reading())
         return 0;
 
-    bool original_blocking = description->is_blocking();
-    if (flags & MSG_DONTWAIT)
-        description->set_blocking(false);
-
     auto data_buffer = TRY(UserOrKernelBuffer::for_user_buffer((u8*)iovs[0].iov_base, iovs[0].iov_len));
     Time timestamp {};
-    auto result = socket.recvfrom(*description, data_buffer, iovs[0].iov_len, flags, user_addr, user_addr_length, timestamp);
-    if (flags & MSG_DONTWAIT)
-        description->set_blocking(original_blocking);
+    bool blocking = (flags & MSG_DONTWAIT) ? false : description->is_blocking();
+    auto result = socket.recvfrom(*description, data_buffer, iovs[0].iov_len, flags, user_addr, user_addr_length, timestamp, blocking);
 
     if (result.is_error())
         return result.release_error();