io_uring: ensure registered buffer import returns the IO length
A test case was reported where two linked reads with registered buffers
failed the second link always. This is because we set the expected value
of a request in req->result, and if we don't get this result, then we
fail the dependent links. For some reason the registered buffer import
returned -ERROR/0, while the normal import returns -ERROR/length. This
broke linked commands with registered buffers.
Fix this by making io_import_fixed() correctly return the mapped length.
Cc: stable@vger.kernel.org # v5.3
Reported-by: 李通洲 <carter.li@eoitek.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 57ea54d..2c819c3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1230,7 +1230,7 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw,
}
}
- return 0;
+ return len;
}
static ssize_t io_import_iovec(struct io_ring_ctx *ctx, int rw,
