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Thu, 04 Dec 2025 14:43:37 -0800 (PST) X-Relaying-Domain: purestorage.com Received: from dev-csander.dev.purestorage.com (unknown [IPv6:2620:125:9007:640:ffff::1199]) by c7-smtp-2023.dev.purestorage.com (Postfix) with ESMTP id D77613400EA; Thu, 4 Dec 2025 15:43:36 -0700 (MST) Received: by dev-csander.dev.purestorage.com (Postfix, from userid 1557716354) id C6533E42318; Thu, 4 Dec 2025 15:43:36 -0700 (MST) From: Caleb Sander Mateos To: Jens Axboe Cc: Caleb Sander Mateos , Joanne Koong , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] io_uring/kbuf: use READ_ONCE() for userspace-mapped memory Date: Thu, 4 Dec 2025 15:43:31 -0700 Message-ID: <20251204224332.1181383-1-csander@purestorage.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 98b6fa62c84f ("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: Caleb Sander Mateos Fixes: c7fb19428d67 ("io_uring: add support for ring mapped supplied buffers") Cc: Joanne Koong --- io_uring/kbuf.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index 8a329556f8df..52b636d00a6b 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -42,11 +42,11 @@ static bool io_kbuf_inc_commit(struct io_buffer_list *bl, int len) buf_len = READ_ONCE(buf->len); this_len = min_t(u32, len, buf_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; } buf->len = 0; bl->head++; @@ -196,13 +196,13 @@ static struct io_br_sel io_ring_buffer_select(struct io_kiocb *req, size_t *len, buf = io_ring_head_to_buf(br, head, bl->mask); buf_len = READ_ONCE(buf->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); sel.buf_list = NULL; } @@ -278,11 +278,11 @@ static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg, /* set it to max, if not set, so we can use it unconditionally */ 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); /* truncate end piece, if needed, for non partial buffers */ if (len > arg->max_len) { @@ -293,11 +293,11 @@ static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg, break; buf->len = len; } } - 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++; arg->out_len += len; arg->max_len -= len; -- 2.45.2