Commit c2c185be authored Mar 12, 2026 by Jens Axboe

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: c7fb1942 ("io_uring: add support for ring mapped supplied buffers")
Reported-by: Keenan Dong <keenanat2000@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 6f02c6b1

io_uring/kbuf.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -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);
		/*
		* 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;