io_uring: correctly handle non ->{read,write}_iter() file_operations

Currently we just -EINVAL a read or write to an fd that isn't backed
by ->read_iter() or ->write_iter(). But we can handle them just fine,
as long as we punt fo async context first.

Implement a simple loop function for doing ->read() or ->write()
instead, and ensure we call it appropriately.

Reported-by: 李通洲 <carter.li@eoitek.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 54 insertions, 6 deletions

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 9d8e703bc851..ca7570aca430 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1298,6 +1298,51 @@ static void io_async_list_note(int rw, struct io_kiocb *req, size_t len)
         }
 }
 
+/*
+ * For files that don't have ->read_iter() and ->write_iter(), handle them
+ * by looping over ->read() or ->write() manually.
+ */
+static ssize_t loop_rw_iter(int rw, struct file *file, struct kiocb *kiocb,
+                           struct iov_iter *iter)
+{
+        ssize_t ret = 0;
+
+        /*
+         * Don't support polled IO through this interface, and we can't
+         * support non-blocking either. For the latter, this just causes
+         * the kiocb to be handled from an async context.
+         */
+        if (kiocb->ki_flags & IOCB_HIPRI)
+                return -EOPNOTSUPP;
+        if (kiocb->ki_flags & IOCB_NOWAIT)
+                return -EAGAIN;
+
+        while (iov_iter_count(iter)) {
+                struct iovec iovec = iov_iter_iovec(iter);
+                ssize_t nr;
+
+                if (rw == READ) {
+                        nr = file->f_op->read(file, iovec.iov_base,
+                                              iovec.iov_len, &kiocb->ki_pos);
+                } else {
+                        nr = file->f_op->write(file, iovec.iov_base,
+                                               iovec.iov_len, &kiocb->ki_pos);
+                }
+
+                if (nr < 0) {
+                        if (!ret)
+                                ret = nr;
+                        break;
+                }
+                ret += nr;
+                if (nr != iovec.iov_len)
+                        break;
+                iov_iter_advance(iter, nr);
+        }
+
+        return ret;
+}
+
 static int io_read(struct io_kiocb *req, const struct sqe_submit *s,
                    bool force_nonblock)
 {
@@ -1315,8 +1360,6 @@ static int io_read(struct io_kiocb *req, const struct sqe_submit *s,
 
         if (unlikely(!(file->f_mode & FMODE_READ)))
                 return -EBADF;
-        if (unlikely(!file->f_op->read_iter))
-                return -EINVAL;
 
         ret = io_import_iovec(req->ctx, READ, s, &iovec, &iter);
         if (ret < 0)
@@ -1331,7 +1374,11 @@ static int io_read(struct io_kiocb *req, const struct sqe_submit *s,
         if (!ret) {
                 ssize_t ret2;
 
-                ret2 = call_read_iter(file, kiocb, &iter);
+                if (file->f_op->read_iter)
+                        ret2 = call_read_iter(file, kiocb, &iter);
+                else
+                        ret2 = loop_rw_iter(READ, file, kiocb, &iter);
+
                 /*
                  * In case of a short read, punt to async. This can happen
                  * if we have data partially cached. Alternatively we can
@@ -1376,8 +1423,6 @@ static int io_write(struct io_kiocb *req, const struct sqe_submit *s,
         file = kiocb->ki_filp;
         if (unlikely(!(file->f_mode & FMODE_WRITE)))
                 return -EBADF;
-        if (unlikely(!file->f_op->write_iter))
-                return -EINVAL;
 
         ret = io_import_iovec(req->ctx, WRITE, s, &iovec, &iter);
         if (ret < 0)
@@ -1415,7 +1460,10 @@ static int io_write(struct io_kiocb *req, const struct sqe_submit *s,
                 }
                 kiocb->ki_flags |= IOCB_WRITE;
 
-                ret2 = call_write_iter(file, kiocb, &iter);
+                if (file->f_op->write_iter)
+                        ret2 = call_write_iter(file, kiocb, &iter);
+                else
+                        ret2 = loop_rw_iter(WRITE, file, kiocb, &iter);
                 if (!force_nonblock || ret2 != -EAGAIN) {
                         io_rw_done(kiocb, ret2);
                 } else {