From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 30D6C26F458; Mon, 7 Apr 2025 18:16:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744049818; cv=none; b=ZNw8d3EAIDh43j4G2bG+kVcD9i3vORIh0+GX7L6PrXgxDjysJNA7xruXYZl6eO9V31bGCInuZYfPyyTWJECDadOSuhoGstKC0LAI4QivMI0QIgH4Re0TUan4eZ8GkDth6KxH5lO5AvwP4Pj/tZRyDueCN1uzxbhf3quzojnYw5I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744049818; c=relaxed/simple; bh=VsAAArcVh6T7g0FJDwhWVlycVOgzVQQT85romacyIqA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=YZ9BxX92oxBc9sreswzgWjFwGyKkJBlc51OPqMbZsELhbLEXhPic0QYqqebOzK4akLQ/wAvp2YovvEbXPW3EcfCfoXnbjOhtnfeCy9jpbGuO5qWjcAYUsaFPvpDYLlI6vEMqqFiNacctb0cF9a1Kzxf+cg2JXY96gRg6SPrF7l4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Dx0Lq9yr; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Dx0Lq9yr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C976C4CEE7; Mon, 7 Apr 2025 18:16:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744049818; bh=VsAAArcVh6T7g0FJDwhWVlycVOgzVQQT85romacyIqA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Dx0Lq9yr3DxkWZtuKoyhALkANaf2aumscJhLIQ2aQ/z9LBVtqFgsAQ7qzQy4vnbr7 UJs/+lKMTZRtNRtF2lr2arb/16YLXchJB/A7RDrEPWo7/oMMFgssNcfkAGhP5NPWSl ZDpe/M7DfHHSc/bBOMcr7w5aXlwoH2+UgHJGI4qdHMrhURh8576mmXf4SXp/55t3eU DfgTUv3yekTB94teGTCW/TptAm8c3koNtUmGOH/7ZBDB6fVoHSenyQMmPVWUlds9Fr hHZjLq4YOfaanCTQs0Ma/6Rzm0kYPwzyrDms028p41iWE6EF+0RoCOzkEDqrFW9RNf Ey4KADozguAuw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Pavel Begunkov , syzbot+903a2ad71fb3f1e47cf5@syzkaller.appspotmail.com, Jens Axboe , Sasha Levin , io-uring@vger.kernel.org Subject: [PATCH AUTOSEL 6.14 9/9] io_uring: always do atomic put from iowq Date: Mon, 7 Apr 2025 14:16:35 -0400 Message-Id: <20250407181635.3184105-9-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250407181635.3184105-1-sashal@kernel.org> References: <20250407181635.3184105-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.14.1 Content-Transfer-Encoding: 8bit From: Pavel Begunkov [ Upstream commit 390513642ee6763c7ada07f0a1470474986e6c1c ] io_uring always switches requests to atomic refcounting for iowq execution before there is any parallilism by setting REQ_F_REFCOUNT, and the flag is not cleared until the request completes. That should be fine as long as the compiler doesn't make up a non existing value for the flags, however KCSAN still complains when the request owner changes oter flag bits: BUG: KCSAN: data-race in io_req_task_cancel / io_wq_free_work ... read to 0xffff888117207448 of 8 bytes by task 3871 on cpu 0: req_ref_put_and_test io_uring/refs.h:22 [inline] Skip REQ_F_REFCOUNT checks for iowq, we know it's set. Reported-by: syzbot+903a2ad71fb3f1e47cf5@syzkaller.appspotmail.com Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/r/d880bc27fb8c3209b54641be4ff6ac02b0e5789a.1743679736.git.asml.silence@gmail.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- io_uring/io_uring.c | 2 +- io_uring/refs.h | 7 +++++++ 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index f7acae5f7e1d0..67c79e576355a 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1774,7 +1774,7 @@ struct io_wq_work *io_wq_free_work(struct io_wq_work *work) struct io_kiocb *req = container_of(work, struct io_kiocb, work); struct io_kiocb *nxt = NULL; - if (req_ref_put_and_test(req)) { + if (req_ref_put_and_test_atomic(req)) { if (req->flags & IO_REQ_LINK_FLAGS) nxt = io_req_find_next(req); io_free_req(req); diff --git a/io_uring/refs.h b/io_uring/refs.h index 63982ead9f7da..0d928d87c4ed1 100644 --- a/io_uring/refs.h +++ b/io_uring/refs.h @@ -17,6 +17,13 @@ static inline bool req_ref_inc_not_zero(struct io_kiocb *req) return atomic_inc_not_zero(&req->refs); } +static inline bool req_ref_put_and_test_atomic(struct io_kiocb *req) +{ + WARN_ON_ONCE(!(data_race(req->flags) & REQ_F_REFCOUNT)); + WARN_ON_ONCE(req_ref_zero_or_close_to_overflow(req)); + return atomic_dec_and_test(&req->refs); +} + static inline bool req_ref_put_and_test(struct io_kiocb *req) { if (likely(!(req->flags & REQ_F_REFCOUNT))) -- 2.39.5