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 C2DBE342526; Tue, 16 Dec 2025 11:26:25 +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=1765884385; cv=none; b=JMDEKMkM56chILil4aYoJ3qPgMHBp8AjuWhdeR3BMQNqB3sCXES53hzsy9c4HzEP3Z8pL5w4pRNW9CW2DSsB4K+ZOFAYAHA1DQJpgatuX9YuUPGToZ89NWPqF7wPS92IvVletihKOm+cy9Yfcm4Rr8kNpjcoc7bK/6ZwLwkpqow= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765884385; c=relaxed/simple; bh=zVjDF2gWWXusloLV1kTdu0bSnNXEBirHExkdyTIFbnU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=u5o00fWWFbZlISJVZwLTslE6zZT4m1Ax389b9LqksbsEvb5lcqMMj1tfqa4aIQDCyylcCNnrdnsLfK9j3rE/0CbMfhIGgaxxwjegHaC+VqJxCRJqD7pcy0xcfFE4soCH+EoIiENwnYdX7Ky0I6jui0fhOusS5uwbE44IqiQhqdw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bSKKvX6D; 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="bSKKvX6D" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2B4BC4CEF5; Tue, 16 Dec 2025 11:26:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1765884385; bh=zVjDF2gWWXusloLV1kTdu0bSnNXEBirHExkdyTIFbnU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bSKKvX6D3eQwysONO3D0+v/ersXKQPF7MWuJ8LD7W+e4fQo/V8ddbiOazHUW07i9A 1UD95TFuBueDGCVzmqTS6KQvXzsp2eet7NpT8vynKSXrXkTNltZAKNXVfiqDqsCRi/ MwmnRjleToSk/W/lei7py4KXArb4HFh2sZ1pH9mc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zheng Qixing , Yu Kuai , Jens Axboe , Sasha Levin Subject: [PATCH 6.12 144/354] nbd: defer config unlock in nbd_genl_connect Date: Tue, 16 Dec 2025 12:11:51 +0100 Message-ID: <20251216111326.133454326@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251216111320.896758933@linuxfoundation.org> References: <20251216111320.896758933@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zheng Qixing [ Upstream commit 1649714b930f9ea6233ce0810ba885999da3b5d4 ] There is one use-after-free warning when running NBD_CMD_CONNECT and NBD_CLEAR_SOCK: nbd_genl_connect nbd_alloc_and_init_config // config_refs=1 nbd_start_device // config_refs=2 set NBD_RT_HAS_CONFIG_REF open nbd // config_refs=3 recv_work done // config_refs=2 NBD_CLEAR_SOCK // config_refs=1 close nbd // config_refs=0 refcount_inc -> uaf ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 24 PID: 1014 at lib/refcount.c:25 refcount_warn_saturate+0x12e/0x290 nbd_genl_connect+0x16d0/0x1ab0 genl_family_rcv_msg_doit+0x1f3/0x310 genl_rcv_msg+0x44a/0x790 The issue can be easily reproduced by adding a small delay before refcount_inc(&nbd->config_refs) in nbd_genl_connect(): mutex_unlock(&nbd->config_lock); if (!ret) { set_bit(NBD_RT_HAS_CONFIG_REF, &config->runtime_flags); + printk("before sleep\n"); + mdelay(5 * 1000); + printk("after sleep\n"); refcount_inc(&nbd->config_refs); nbd_connect_reply(info, nbd->index); } Fixes: e46c7287b1c2 ("nbd: add a basic netlink interface") Signed-off-by: Zheng Qixing Reviewed-by: Yu Kuai Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/block/nbd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index e6b756c475cde..958bd115a3417 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -2169,12 +2169,13 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) ret = nbd_start_device(nbd); out: - mutex_unlock(&nbd->config_lock); if (!ret) { set_bit(NBD_RT_HAS_CONFIG_REF, &config->runtime_flags); refcount_inc(&nbd->config_refs); nbd_connect_reply(info, nbd->index); } + mutex_unlock(&nbd->config_lock); + nbd_config_put(nbd); if (put_dev) nbd_put(nbd); -- 2.51.0