[PATCH AUTOSEL 5.10 39/39] io_uring: call req_set_fail_links() on short send[msg]()/recv[msg]() with MSG_WAITALL

Sasha Levin
2021-03-25T11:32:59Z

From: Stefan Metzmacher <metze@samba.org>

[ Upstream commit 0031275d119efe16711cd93519b595e6f9b4b330 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io_uring.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 38a394c6260d..f8a47cebeacd 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4390,6 +4390,7 @@ static int io_sendmsg(struct io_kiocb *req, bool force_nonblock,
struct io_async_msghdr iomsg, *kmsg;
struct socket *sock;
unsigned flags;
+ int min_ret = 0;
int ret;

sock = sock_from_file(req->file, &ret);
@@ -4416,6 +4417,9 @@ static int io_sendmsg(struct io_kiocb *req, bool force_nonblock,
else if (force_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 (force_nonblock && ret == -EAGAIN)
return io_setup_async_msg(req, kmsg);
@@ -4425,7 +4429,7 @@ static int io_sendmsg(struct io_kiocb *req, bool force_nonblock,
if (kmsg->iov != kmsg->fast_iov)
kfree(kmsg->iov);
req->flags &= ~REQ_F_NEED_CLEANUP;
- if (ret < 0)
+ if (ret < min_ret)
req_set_fail_links(req);
__io_req_complete(req, ret, 0, cs);
return 0;
@@ -4439,6 +4443,7 @@ static int io_send(struct io_kiocb *req, bool force_nonblock,
struct iovec iov;
struct socket *sock;
unsigned flags;
+ int min_ret = 0;
int ret;

sock = sock_from_file(req->file, &ret);
@@ -4460,6 +4465,9 @@ static int io_send(struct io_kiocb *req, bool force_nonblock,
else if (force_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 (force_nonblock && ret == -EAGAIN)
@@ -4467,7 +4475,7 @@ static int io_send(struct io_kiocb *req, bool force_nonblock,
if (ret == -ERESTARTSYS)
ret = -EINTR;

- if (ret < 0)
+ if (ret < min_ret)
req_set_fail_links(req);
__io_req_complete(req, ret, 0, cs);
return 0;
@@ -4619,6 +4627,7 @@ static int io_recvmsg(struct io_kiocb *req, bool force_nonblock,
struct socket *sock;
struct io_buffer *kbuf;
unsigned flags;
+ int min_ret = 0;
int ret, cflags = 0;

sock = sock_from_file(req->file, &ret);
@@ -4654,6 +4663,9 @@ static int io_recvmsg(struct io_kiocb *req, bool force_nonblock,
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)
@@ -4666,7 +4678,7 @@ static int io_recvmsg(struct io_kiocb *req, bool force_nonblock,
if (kmsg->iov != kmsg->fast_iov)
kfree(kmsg->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, ret, cflags, cs);
return 0;
@@ -4682,6 +4694,7 @@ static int io_recv(struct io_kiocb *req, bool force_nonblock,
struct socket *sock;
struct iovec iov;
unsigned flags;
+ int min_ret = 0;
int ret, cflags = 0;

sock = sock_from_file(req->file, &ret);
@@ -4712,6 +4725,9 @@ static int io_recv(struct io_kiocb *req, bool force_nonblock,
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;
@@ -4720,7 +4736,7 @@ static int io_recv(struct io_kiocb *req, bool force_nonblock,
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, ret, cflags, cs);
return 0;
--
2.30.1