Commit 78385c72 authored by Caleb Sander Mateos's avatar Caleb Sander Mateos Committed by Jens Axboe
Browse files

io_uring/kbuf: use READ_ONCE() for userspace-mapped memory 



The struct io_uring_buf elements in a buffer ring are in a memory region
accessible from userspace. A malicious/buggy userspace program could
therefore write to them at any time, so they should be accessed with
READ_ONCE() in the kernel. Commit 98b6fa62 ("io_uring/kbuf: always
use READ_ONCE() to read ring provided buffer lengths") already switched
the reads of the len field to READ_ONCE(). Do the same for bid and addr.

Signed-off-by: default avatarCaleb Sander Mateos <csander@purestorage.com>
Fixes: c7fb1942 ("io_uring: add support for ring mapped supplied buffers")
Cc: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 525916ce

io_uring/kbuf.c

+5 −5
Original line number Diff line number Diff line
@@ -44,7 +44,7 @@ static bool io_kbuf_inc_commit(struct io_buffer_list *bl, int len) 
		buf_len -= this_len;

		/* Stop looping for invalid buffer length of 0 */

		if (buf_len || !this_len) {

			buf->addr += this_len;

			buf->addr = READ_ONCE(buf->addr) + this_len;

			buf->len = buf_len;

			return false;

		}
@@ -198,9 +198,9 @@ static struct io_br_sel io_ring_buffer_select(struct io_kiocb *req, size_t *len, 
	if (*len == 0 || *len > buf_len)

		*len = buf_len;

	req->flags |= REQ_F_BUFFER_RING | REQ_F_BUFFERS_COMMIT;

	req->buf_index = buf->bid;

	req->buf_index = READ_ONCE(buf->bid);

	sel.buf_list = bl;

	sel.addr = u64_to_user_ptr(buf->addr);

	sel.addr = u64_to_user_ptr(READ_ONCE(buf->addr));



	if (io_should_commit(req, issue_flags)) {

		io_kbuf_commit(req, sel.buf_list, *len, 1);
@@ -280,7 +280,7 @@ static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg, 
	if (!arg->max_len)

		arg->max_len = INT_MAX;



	req->buf_index = buf->bid;

	req->buf_index = READ_ONCE(buf->bid);

	do {

		u32 len = READ_ONCE(buf->len);
@@ -295,7 +295,7 @@ static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg, 
			}

		}



		iov->iov_base = u64_to_user_ptr(buf->addr);

		iov->iov_base = u64_to_user_ptr(READ_ONCE(buf->addr));

		iov->iov_len = len;

		iov++;