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 62D6B3191D2; Fri, 9 Jan 2026 12:29:48 +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=1767961788; cv=none; b=ni+HFxy4KXyBFx3z3VKIqz67PbL6JA7s4sWV6ZFisqjsXoDwMruI960TjapFyXibvjU779ERJrn5OJEWbMighibBlGhvSmgsDB/JisevC5ROinu5RDJ/2Om7OizxOmO9R0tX545pGtB4lXhBPU+79F33YWYdwZ2NBsAsYc0bq0A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767961788; c=relaxed/simple; bh=RwcYMYUJ/u6DcDvpyrkO+h7I8ppD13fEShLCzuGXwMg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ug7acXAs1+iO2CpzRU6nKNjkX/VNnluyLnOcXaJGq6NIVSr7NaKfWavJWxuy0IPZmgXlKO1cd0L9YKha9qNBJspu0suR/KmoX221iViGXxpIsfAzOUThpPlYwi8NxgaggbXKJqmcJurPPJXvGJEY9qzUQJKwjv+mO9L0syAEmXA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=OIDG9fFn; 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="OIDG9fFn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E38C6C4CEF1; Fri, 9 Jan 2026 12:29:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767961788; bh=RwcYMYUJ/u6DcDvpyrkO+h7I8ppD13fEShLCzuGXwMg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OIDG9fFnW79R5fsLjPzKjMY25yO0RcYcOKrZ1BVDXXWCd87FUzjiC2d1JrLY2wV7U v9LcgPQO2mE1EzXm+3EurVUaHUV3GKJkMC47wBVnahHgc2iHfeelTzRsAoVNs7u9iL Vl4qN94j9aSIBTU/UdYewCJDDINQEOqvMPKwGDsc= 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 6.1 103/634] nbd: defer config unlock in nbd_genl_connect Date: Fri, 9 Jan 2026 12:36:21 +0100 Message-ID: <20260109112121.308489611@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260109112117.407257400@linuxfoundation.org> References: <20260109112117.407257400@linuxfoundation.org> User-Agent: quilt/0.69 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 6.1-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 80a2d346a51cc..008534aad0a18 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -2116,12 +2116,13 @@ 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