io_uring: call req_set_fail_links() on short send[msg]()/recv[msg]() with MSG_WAITALL

Without that it's not safe to use them in a linked combination with
others.

Now combinations like IORING_OP_SENDMSG followed by IORING_OP_SPLICE
should be possible.

We already handle short reads and writes for the following opcodes:

- IORING_OP_READV
- IORING_OP_READ_FIXED
- IORING_OP_READ
- IORING_OP_WRITEV
- IORING_OP_WRITE_FIXED
- IORING_OP_WRITE
- IORING_OP_SPLICE
- IORING_OP_TEE

Now we have it for these as well:

- IORING_OP_SENDMSG
- IORING_OP_SEND
- IORING_OP_RECVMSG
- IORING_OP_RECV

For IORING_OP_RECVMSG we also check for the MSG_TRUNC and MSG_CTRUNC
flags in order to call req_set_fail_links().

There might be applications arround depending on the behavior
that even short send[msg]()/recv[msg]() retuns continue an
IOSQE_IO_LINK chain.

It's very unlikely that such applications pass in MSG_WAITALL,
which is only defined in 'man 2 recvmsg', but not in 'man 2 sendmsg'.

It's expected that the low level sock_sendmsg() call just ignores
MSG_WAITALL, as MSG_ZEROCOPY is also ignored without explicitly set
SO_ZEROCOPY.

We also expect the caller to know about the implicit truncation to
MAX_RW_COUNT, which we don't detect.

cc: netdev@vger.kernel.org
Link: https://lore.kernel.org/r/c4e1a4cc0d905314f4d5dc567e65a7b09621aab3.1615908477.git.metze@samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ea2d3e1..543551d 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4386,6 +4386,7 @@ static int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
        struct io_async_msghdr iomsg, *kmsg;
        struct socket *sock;
        unsigned flags;
+       int min_ret = 0;
        int ret;
 
        sock = sock_from_file(req->file);
@@ -4406,6 +4407,9 @@ static int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
        else if (issue_flags & IO_URING_F_NONBLOCK)
                flags |= MSG_DONTWAIT;
 
+       if (flags & MSG_WAITALL)
+               min_ret = iov_iter_count(&kmsg->msg.msg_iter);
+
        ret = __sys_sendmsg_sock(sock, &kmsg->msg, flags);
        if ((issue_flags & IO_URING_F_NONBLOCK) && ret == -EAGAIN)
                return io_setup_async_msg(req, kmsg);
@@ -4416,7 +4420,7 @@ static int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
        if (kmsg->free_iov)
                kfree(kmsg->free_iov);
        req->flags &= ~REQ_F_NEED_CLEANUP;
-       if (ret < 0)
+       if (ret < min_ret)
                req_set_fail_links(req);
        __io_req_complete(req, issue_flags, ret, 0);
        return 0;
@@ -4429,6 +4433,7 @@ static int io_send(struct io_kiocb *req, unsigned int issue_flags)
        struct iovec iov;
        struct socket *sock;
        unsigned flags;
+       int min_ret = 0;
        int ret;
 
        sock = sock_from_file(req->file);
@@ -4450,6 +4455,9 @@ static int io_send(struct io_kiocb *req, unsigned int issue_flags)
        else if (issue_flags & IO_URING_F_NONBLOCK)
                flags |= MSG_DONTWAIT;
 
+       if (flags & MSG_WAITALL)
+               min_ret = iov_iter_count(&msg.msg_iter);
+
        msg.msg_flags = flags;
        ret = sock_sendmsg(sock, &msg);
        if ((issue_flags & IO_URING_F_NONBLOCK) && ret == -EAGAIN)
@@ -4457,7 +4465,7 @@ static int io_send(struct io_kiocb *req, unsigned int issue_flags)
        if (ret == -ERESTARTSYS)
                ret = -EINTR;
 
-       if (ret < 0)
+       if (ret < min_ret)
                req_set_fail_links(req);
        __io_req_complete(req, issue_flags, ret, 0);
        return 0;
@@ -4609,6 +4617,7 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
        struct socket *sock;
        struct io_buffer *kbuf;
        unsigned flags;
+       int min_ret = 0;
        int ret, cflags = 0;
        bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
 
@@ -4640,6 +4649,9 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
        else if (force_nonblock)
                flags |= MSG_DONTWAIT;
 
+       if (flags & MSG_WAITALL)
+               min_ret = iov_iter_count(&kmsg->msg.msg_iter);
+
        ret = __sys_recvmsg_sock(sock, &kmsg->msg, req->sr_msg.umsg,
                                        kmsg->uaddr, flags);
        if (force_nonblock && ret == -EAGAIN)
@@ -4653,7 +4665,7 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
        if (kmsg->free_iov)
                kfree(kmsg->free_iov);
        req->flags &= ~REQ_F_NEED_CLEANUP;
-       if (ret < 0)
+       if (ret < min_ret || ((flags & MSG_WAITALL) && (kmsg->msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC))))
                req_set_fail_links(req);
        __io_req_complete(req, issue_flags, ret, cflags);
        return 0;
@@ -4668,6 +4680,7 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
        struct socket *sock;
        struct iovec iov;
        unsigned flags;
+       int min_ret = 0;
        int ret, cflags = 0;
        bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
 
@@ -4699,6 +4712,9 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
        else if (force_nonblock)
                flags |= MSG_DONTWAIT;
 
+       if (flags & MSG_WAITALL)
+               min_ret = iov_iter_count(&msg.msg_iter);
+
        ret = sock_recvmsg(sock, &msg, flags);
        if (force_nonblock && ret == -EAGAIN)
                return -EAGAIN;
@@ -4707,7 +4723,7 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 out_free:
        if (req->flags & REQ_F_BUFFER_SELECTED)
                cflags = io_put_recv_kbuf(req);
-       if (ret < 0)
+       if (ret < min_ret || ((flags & MSG_WAITALL) && (msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC))))
                req_set_fail_links(req);
        __io_req_complete(req, issue_flags, ret, cflags);
        return 0;