From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792680606; b=MjMHpssuZPWLPsnCLen6Pjvv4wX8nAnARYVkVCYq7lMa0N/CEIq3AqETY8QEgybBey1Z mEZjIFklQoNLgTs/yq6N2KMDxwF7xlKO9yPdTQQwmhE7esBXPjCR64d1GD/oShoUg4DL1 LiZzhZ5kDtdW2RWjAu8KHoMNjBmfdI7LRyNQ6ScpESgR3BtkzrJwVFTIKSLwZMmu20Mee BjKDO2p3/rCLtYOLTzenz2pI99xUGj9Flo/kZuW2Z57qR1Hk/O3J5FWoNljOOfB4s5vTA IOFURputEweJKeiyJdVrsvopwmXwECR0AqVOoHpwvnA3kXesHRSO7+WzNTFtwOK2TPA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792680606; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=0nxzWjWTncpXKqMiUQkEcupUXgWcJgw0HwU/2CIau6I=; b=VgNUDs4AMiI10FXiT794MTHttqY5g0CtnQ3/VGmkO451+//g7VNyY4ShvSNypfqLwaou 8bzY7EgakTUbFh9y+Izb9ynH8waaCoktCWg+G1OGX3fZFXQT4iu48KonVWLBdHJ7+XWBJ KrvRpLZJHo16YY/+3jgXzZZmYQdfy6PUxn6rATQIqat+6pw7WWv5+r+oqAeBw/V2/YtFe XxfBXvaxCvzpM/d0E5PmkdE6ClGFvFXjeqWMidKwh9yt0vxYeSqKH1GrdhmOJChOTMaxI 74p11sHG9mzqi46jQcMWgJQUcrGwhZS39YF5dRxg1B+x7yASaLaYMmkdXLmfaN6HobA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=IegnJPI5; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D2CE5606A320 for ; Thu, 22 Oct 2026 14:50:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=IegnJPI5 Received: by smtp.kernel.org (Postfix) with ESMTPSA id E411D1F000C1; Thu, 22 Oct 2026 14:50:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792680605; bh=0nxzWjWTncpXKqMiUQkEcupUXgWcJgw0HwU/2CIau6I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=IegnJPI56vm8KFSwf70GBi3SOvkws8wlmGj1j8PF3NEny7oHK06brPzBBnXV7y5Ey GtKuMwHT1D7WSkEUBVTayGvCeQzKedd/5eKFnFftktQWMBsaUvJqtgOU1QuzOfIU34 psnBpjbul04771rvRgPqC9AR+FFNwGPXBg4hPjfgklqq/T0lgeG2QUbHcv2eZgj0bQ 0X0yXp1s8kHqvlfQKyXUcsNEoTnkqONF/GO88ktiOG2EZuBtUqL1HPpl5hEa52dCsm a1Os6ue7HdT8ZxR5c4a3/wXDtteYnxV1a9Q2JGhuOSQkHSxrx6jGw2KCp3YY0ZFB7Z Sm8fThYRYkuBQ== From: Sasha Levin To: stable@vger.kernel.org Cc: "Cen Zhang (Microsoft Security FORGE Labs)" , AutonomousCodeSecurity@microsoft.com, Jens Axboe , Sasha Levin Subject: [PATCH 6.12.y] io_uring/cancel: don't spin on local work the task can't run Date: Thu, 22 Oct 2026 10:50:03 -0400 Message-ID: <20261022144856.1619302-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026102128-salvation-quack-0ba4@gregkh> References: <2026102128-salvation-quack-0ba4@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Cen Zhang (Microsoft Security FORGE Labs)" [ Upstream commit fddcf4c5321b3ea5f72166c3fd36a9d1c34f80c7 ] io_uring_cancel_generic() refuses to sleep while any ring on the exiting task's tctx has local work pending. It assumes the task is that ring's submitter and that the next io_uring_try_cancel_requests() pass will run the work. This does not hold for a ring that was still IORING_SETUP_R_DISABLED when the task got its tctx node from io_uring_create() or io_ringfd_register(). The submitter is set later by IORING_REGISTER_ENABLE_RINGS, possibly from another task, and only the submitter may run local work on an IORING_SETUP_DEFER_TASKRUN ring. To the exiting task the work stays pending forever, the loop never reaches schedule(), and the task trips the WARN_ON_ONCE() once and then spins in do_exit(). An unprivileged user can set this up at will by creating a disabled ring, having a child enable it and stop, posting to the ring with IORING_OP_MSG_RING and exiting with a request in flight that only the child can complete. The exiting thread burns a CPU until the child runs or dies, and with panic_on_warn set the WARN panics the kernel. Fix by skipping the sleep only when io_allowed_defer_tw_run() allows the task to run the work. This is reasonable since work it cannot run cannot complete any of its requests either, so nothing is lost by sleeping. Drop the WARN_ON_ONCE() since handing a disabled ring to another thread is a supported scenario, not a bug state. Fixes: 360cd42c4e95 ("io_uring: optimise io_req_local_work_add") Reported-by: AutonomousCodeSecurity@microsoft.com Signed-off-by: Cen Zhang (Microsoft Security FORGE Labs) Link: https://patch.msgid.link/20261008191602.45101-1-cenzhang@linux.microsoft.com Signed-off-by: Jens Axboe [ sashal: Used !llist_empty(&node->ctx->work_llist) instead of the unavailable io_local_work_pending() helper. ] Signed-off-by: Sasha Levin --- io_uring/io_uring.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 0076c7599c947..68a21552a186f 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -3190,12 +3190,11 @@ __cold void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd) prepare_to_wait(&tctx->wait, &wait, TASK_INTERRUPTIBLE); io_run_task_work(); io_uring_drop_tctx_refs(current); + /* only skip the sleep for local work this task may run */ xa_for_each(&tctx->xa, index, node) { - if (!llist_empty(&node->ctx->work_llist)) { - WARN_ON_ONCE(node->ctx->submitter_task && - node->ctx->submitter_task != current); + if (!llist_empty(&node->ctx->work_llist) && + io_allowed_defer_tw_run(node->ctx)) goto end_wait; - } } /* * If we've seen completions, retry without waiting. This -- 2.53.0