From: Dylan Yudaken <dylany@fb.com>
Date: Thu, 30 Jun 2022 09:12:20 +0000 (-0700)
Subject: io_uring: allow 0 length for buffer select
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b8c015598c8ef9195b8a2a5089e275c4f64ca999;p=linux.git

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@fb.com>
Link: https://lore.kernel.org/r/20220630091231.1456789-2-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 5e00f16e89b86..e538fa7cb727c 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;