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 6A09A1F5EBE; Fri, 4 Oct 2024 18:22:56 +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=1728066176; cv=none; b=kK2bJnNc/TJgRAR6+CiJHBUsOJXEgytd4ozkcrKxtsjWg8I3dYEV6QTScio8M+FtJeMPOiP1LynhyNnz7U8HXTiuqrk18iqVa6bA2tWrJzinFZllc/M8vqHMoRI505awVxfWabl6Rwgd2eRAYcEAvuklM3AJypQzSh0WEV+bxlA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728066176; c=relaxed/simple; bh=eD6tgJpXpuwcA0P/8bt187/KbE9ZeB+577xiRd3iLOs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dzpUPslQimPTZbXPMGkCbx9WQY4msZn+D59GV4doQ+Lo1DG3RfvbEgqfWDDQowb5V3/mew0M88eRHVdMfWZjBSISqFfMiZOy2+5telFg3g13Jv5UCpoMOTei881cpqTwJtMmk1tqPZo8KrWfDl4Ncc3X12yUZSaQqT6L0+dlUzE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XLb4aUxX; 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="XLb4aUxX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 795E9C4CECC; Fri, 4 Oct 2024 18:22:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728066176; bh=eD6tgJpXpuwcA0P/8bt187/KbE9ZeB+577xiRd3iLOs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XLb4aUxXw4kWyGoDjBM23gSS2P4rJy79kj4fr8tiWzgdQt3IyATMgMaQTI5s8URsU 1xDpgSSvs38/9TRAKN2CBfaf7ThugWVm/ATRZXCuKvU/2Iaq229xUw5quW5yFrCbjr k8nn67YuwAQq9PGdkPuAYRjME7hPphwtjv/peZwL5K2uar+481S29a80O+ZFIi/6jW L1b57tIPrvAKJGpUVfZS33KLFWfcaSvmIAPLud0BdRJ8IpQFjxX/ZcfWNmNReU0tYB J47F1zgy839O7WOdzAkcgyA67eg/DfqsBP0/uOiM8Npk/WJWLdDppCvlX3vSTAoL5E oB3Klir2FK84g== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Jens Axboe , syzbot+5fca234bd7eb378ff78e@syzkaller.appspotmail.com, Sasha Levin , asml.silence@gmail.com, io-uring@vger.kernel.org Subject: [PATCH AUTOSEL 6.10 31/70] io_uring: check if we need to reschedule during overflow flush Date: Fri, 4 Oct 2024 14:20:29 -0400 Message-ID: <20241004182200.3670903-31-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241004182200.3670903-1-sashal@kernel.org> References: <20241004182200.3670903-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.10.13 Content-Transfer-Encoding: 8bit From: Jens Axboe [ Upstream commit eac2ca2d682f94f46b1973bdf5e77d85d77b8e53 ] In terms of normal application usage, this list will always be empty. And if an application does overflow a bit, it'll have a few entries. However, nothing obviously prevents syzbot from running a test case that generates a ton of overflow entries, and then flushing them can take quite a while. Check for needing to reschedule while flushing, and drop our locks and do so if necessary. There's no state to maintain here as overflows always prune from head-of-list, hence it's fine to drop and reacquire the locks at the end of the loop. Link: https://lore.kernel.org/io-uring/66ed061d.050a0220.29194.0053.GAE@google.com/ Reported-by: syzbot+5fca234bd7eb378ff78e@syzkaller.appspotmail.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- io_uring/io_uring.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 896e707e06187..f295102789cef 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -696,6 +696,21 @@ static void __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool dying) } list_del(&ocqe->list); kfree(ocqe); + + /* + * For silly syzbot cases that deliberately overflow by huge + * amounts, check if we need to resched and drop and + * reacquire the locks if so. Nothing real would ever hit this. + * Ideally we'd have a non-posting unlock for this, but hard + * to care for a non-real case. + */ + if (need_resched()) { + io_cq_unlock_post(ctx); + mutex_unlock(&ctx->uring_lock); + cond_resched(); + mutex_lock(&ctx->uring_lock); + io_cq_lock(ctx); + } } if (list_empty(&ctx->cq_overflow_list)) { -- 2.43.0