From 2bec95d7a4e576201c41380432f88cfc63cca107 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Stefan=20B=C3=BChler?= Date: Thu, 15 Apr 2021 17:30:50 +0800 Subject: [PATCH] io_uring: fix race condition when sq threads goes sleeping MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit mainline inclusion from mainline-5.1-rc7 commit 0d7bae69c574c5f25802f8a71252e7d66933a3ab category: feature bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27 CVE: NA --------------------------- Reading the SQ tail needs to come after setting IORING_SQ_NEED_WAKEUP in flags; there is no cheap barrier for ordering a store before a load, a full memory barrier is required. Userspace needs a full memory barrier between updating SQ tail and checking for the IORING_SQ_NEED_WAKEUP too. Signed-off-by: Stefan Bühler Signed-off-by: Jens Axboe Signed-off-by: Zhihao Cheng Signed-off-by: yangerkun Reviewed-by: zhangyi (F) Signed-off-by: Cheng Jian --- fs/io_uring.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 9507ef2b399e..68f0ac9470c3 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1862,7 +1862,8 @@ static int io_sq_thread(void *data) /* Tell userspace we may need a wakeup call */ ctx->sq_ring->flags |= IORING_SQ_NEED_WAKEUP; - smp_wmb(); + /* make sure to read SQ tail after writing flags */ + smp_mb(); if (!io_get_sqring(ctx, &sqes[0])) { if (kthread_should_stop()) { -- GitLab