[PATCH] io_files_update_prep shouldn't consider all the flags invalid

[Daniele Salvatore Albano <d.albano@gmail.com>]

Currently when an IORING_OP_FILES_UPDATE is submitted with the
IOSQE_IO_LINK flag it fails with EINVAL even if it's considered a
valid because the expectation is that there are no flags set for the
sqe.

The patch updates the check to allow IOSQE_IO_LINK and ensure that
EINVAL is returned only for IOSQE_FIXED_FILE and IOSQE_BUFFER_SELECT.

Signed-off-by: Daniele Albano <d.albano@gmail.com>
---
 fs/io_uring.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ba70dc62f15f..7058b1a0bd39 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5205,7 +5205,14 @@ static int io_async_cancel(struct io_kiocb *req)
 static int io_files_update_prep(struct io_kiocb *req,
                                const struct io_uring_sqe *sqe)
 {
-       if (sqe->flags || sqe->ioprio || sqe->rw_flags)
+       unsigned flags = 0;
+
+       if (sqe->ioprio || sqe->rw_flags)
+               return -EINVAL;
+
+       flags = READ_ONCE(sqe->flags);
+
+       if (flags & (IOSQE_FIXED_FILE | IOSQE_BUFFER_SELECT))
                return -EINVAL;

        req->files_update.offset = READ_ONCE(sqe->off);
--
2.25.1