io_uring/kbuf: check if target buffer list is still legacy on recycle

There's a gap between when the buffer was grabbed and when it
potentially gets recycled, where if the list is empty, someone could've
upgraded it to a ring provided type. This can happen if the request
is forced via io-wq. The legacy recycling is missing checking if the
buffer_list still exists, and if it's of the correct type. Add those
checks.

Cc: stable@vger.kernel.org
Fixes: c7fb19428d67 ("io_uring: add support for ring mapped supplied buffers")
Reported-by: Keenan Dong <keenanat2000@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index dae5b4ab3819c632b5c5305340c7bea4c44f2009..e7f444953dfb3d5ff8834f6894ab109c09c5a4cd 100644 (file)
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -111,9 +111,18 @@ bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
 
        buf = req->kbuf;
        bl = io_buffer_get_list(ctx, buf->bgid);
-       list_add(&buf->list, &bl->buf_list);
-       bl->nbufs++;
+       /*
+        * If the buffer list was upgraded to a ring-based one, or removed,
+        * while the request was in-flight in io-wq, drop it.
+        */
+       if (bl && !(bl->flags & IOBL_BUF_RING)) {
+               list_add(&buf->list, &bl->buf_list);
+               bl->nbufs++;
+       } else {
+               kfree(buf);
+       }
        req->flags &= ~REQ_F_BUFFER_SELECTED;
+       req->kbuf = NULL;
 
        io_ring_submit_unlock(ctx, issue_flags);
        return true;