linux-kernel - [PATCH v2 for-next 01/12] io_uring: allow 0 length for buffer select

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Date:   Thu, 30 Jun 2022 02:12:20 -0700
From:   Dylan Yudaken <dylany@...com>
To:     Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>,
        <io-uring@...r.kernel.org>
CC:     <Kernel-team@...com>, <linux-kernel@...r.kernel.org>,
        Dylan Yudaken <dylany@...com>
Subject: [PATCH v2 for-next 01/12] io_uring: allow 0 length for buffer select

If user gives 0 for length, we can set it from the available buffer size.

Signed-off-by: Dylan Yudaken <dylany@...com>
---
 io_uring/kbuf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 8e4f1e8aaf4a..4ed5102461bf 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -115,7 +115,7 @@ static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
 
 		kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
 		list_del(&kbuf->list);
-		if (*len > kbuf->len)
+		if (*len == 0 || *len > kbuf->len)
 			*len = kbuf->len;
 		req->flags |= REQ_F_BUFFER_SELECTED;
 		req->kbuf = kbuf;
@@ -145,7 +145,7 @@ static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len,
 		buf = page_address(bl->buf_pages[index]);
 		buf += off;
 	}
-	if (*len > buf->len)
+	if (*len == 0 || *len > buf->len)
 		*len = buf->len;
 	req->flags |= REQ_F_BUFFER_RING;
 	req->buf_list = bl;
-- 
2.30.2