[PATCH 5.5 223/367] io_uring: dont map read/write iovec potentially twice

Greg Kroah-Hartman
2020-02-10T12:59:55Z

From: Jens Axboe <axboe@kernel.dk>

commit 5d204bcfa09330972ad3428a8f81c23f371d3e6d upstream.

If we have a read/write that is deferred, we already setup the async IO
context for that request, and mapped it. When we later try and execute
the request and we get -EAGAIN, we don't want to attempt to re-map it.
If we do, we end up with garbage in the iovec, which typically leads
to an -EFAULT or -EINVAL completion.

Cc: stable@vger.kernel.org # 5.5
Reported-by: Dan Melnic <dmm@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/io_uring.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1789,10 +1789,12 @@ static int io_setup_async_rw(struct io_k
if (req->opcode == IORING_OP_READ_FIXED ||
req->opcode == IORING_OP_WRITE_FIXED)
return 0;
- if (!req->io && io_alloc_async_ctx(req))
- return -ENOMEM;
+ if (!req->io) {
+ if (io_alloc_async_ctx(req))
+ return -ENOMEM;

- io_req_map_rw(req, io_size, iovec, fast_iov, iter);
+ io_req_map_rw(req, io_size, iovec, fast_iov, iter);
+ }
req->work.func = io_rw_async;
return 0;
}