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 2394B1A0BE7; Mon, 14 Oct 2024 14:25:25 +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=1728915925; cv=none; b=jjxPu/xZw359KG799Wviv49BtpFDIXKzH+K4lK3hRfBiV7i+Z0fa7k/WNeM3rkif0WYtzWCAWsz+rH5ZujHK1nqzyPlzf60hJDaYp31tvUyzrmMjR7J9gf3DVUub2GEiYUH/5HeP0ZNh0eFjisAoeVUPKQ2T74Z+HAb4gT+4qXM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728915925; c=relaxed/simple; bh=iIuu1rMdxUQUFhvIpHWx7+RTSiVu2bjRUnGsEPzYQ44=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=G4lKRmvh0CDeWARhqrf6JyXp+KXW0rH+K8bUzM4KHVObcMxE0R7RIhuwgSTvVCAco3RMF1uMYfag6pPb4iqD1O9YtT14N/5+YIRC2tV7hAbjLDf5O0vBTbQyaqdKl2CHWBdrQKbPvqHHqjeEvxqNX0TbHkoPu2lHZ2Ogjww2EUM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=M0Xr1kSd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="M0Xr1kSd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8A954C4CEC3; Mon, 14 Oct 2024 14:25:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1728915925; bh=iIuu1rMdxUQUFhvIpHWx7+RTSiVu2bjRUnGsEPzYQ44=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=M0Xr1kSdSA49vXLJEoiQ/KNxMsIqmHVrhgWsr341UdvOeWl24SKHxo7u+mplMpq0K KLWNt4ip+eIyff6CTGEaPqYE6IRTDM+EMz7AcBafxsOUSeUJJdMedRkJdJjMtAAe0F hDUMLjm9dpT+AVRhe9rxVYOBeZiwHSdeAqEpSMpQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+5fca234bd7eb378ff78e@syzkaller.appspotmail.com, Jens Axboe , Sasha Levin Subject: [PATCH 6.11 039/214] io_uring: check if we need to reschedule during overflow flush Date: Mon, 14 Oct 2024 16:18:22 +0200 Message-ID: <20241014141046.516220094@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241014141044.974962104@linuxfoundation.org> References: <20241014141044.974962104@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.11-stable review patch. If anyone has any objections, please let me know. ------------------ 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 7a166120a45c3..7057d942fb2b0 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -627,6 +627,21 @@ 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