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 1A33A37A839; Mon, 13 Jul 2026 11:07:54 +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=1783940874; cv=none; b=OyI/YAUarbzGH0KlaQM4b/K4lyUPY6MwuvQqaDmOoAlHZHh+RGuKAh4XGUe6rTgjfP/KlkFhlTQMa0M/oYwjC2+MV+a0mQ1hENCghp+rY+NSloYVZ8hSBiyU1P6ns5uKluT908YKQ6sO6qj928/wGXctd8qUNLKoW4/+q0LcOxk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783940874; c=relaxed/simple; bh=gFPfNAZb5Emut5tl59jtS1GCSawh67g0IOaptPFibj4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=GWYRxsUty+wLcsMpnbfHJJWMAUu8+8jg62cmjmBdts+oKht/WX+5IAVEMeG196UjLjXIRY+tevO3TN/vQ4coFP92r16LPo97nj67/Gium+xE7jGhMg7f70WlrjDV0JTq8UDb1EbWEUVw4AXbP2LIOxytiN3ejksN2GhuHynSN8o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OoTPnIF6; 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="OoTPnIF6" Received: by smtp.kernel.org (Postfix) with ESMTPS id C59C1C2BCF5; Mon, 13 Jul 2026 11:07:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1783940873; bh=gFPfNAZb5Emut5tl59jtS1GCSawh67g0IOaptPFibj4=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=OoTPnIF6SRLmVMupyhjeUKZcJU6AwKweMwZvPnhmtHyFwjFGZN6LED68Pg9kUqDIh QnIthYMOQS0FSZyN1buNkwC7IBnD/H8mjUCso0YSIVQgD3rz7hwLyyHbzgQHsM/7et ZMhrwojxoZ1IP71Bxifb4A/pv98lRSCNrDNqk2b+hWFAtomwindDIrfc8DsdmItmku 9UWDy/4ZhoDm6QwHErqcuP1uhsqGZI4fOzzRpLoXobSgVpMST0T+HlbbsFjoxIVHg/ J3TRolG2lzwG4pisXO7RHNB6bmwRtJM2ALur1waxVeb26jVXjtOo06m7mJb102PZH8 SjIX+F9U8UW0w== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id A3BBCC44507; Mon, 13 Jul 2026 11:07:53 +0000 (UTC) From: Joel Granados Date: Mon, 13 Jul 2026 13:07:42 +0200 Subject: [PATCH RFC net-next v3 1/3] net: enforce net sysctl registration Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260713-jag-net_const_qualify-v3-1-7289fe9eaea6@kernel.org> References: <20260713-jag-net_const_qualify-v3-0-7289fe9eaea6@kernel.org> In-Reply-To: <20260713-jag-net_const_qualify-v3-0-7289fe9eaea6@kernel.org> To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , David Ahern , Ido Schimmel , Pablo Neira Ayuso , Florian Westphal , Phil Sutter , Marcelo Ricardo Leitner , Xin Long , Steffen Klassert , Herbert Xu , "D. Wythe" , Dust Li , Sidraya Jayagond , Wenjia Zhang , Mahanta Jambigi , Tony Lu , Wen Gu , Kuniyuki Iwashima , Stefano Garzarella Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, linux-sctp@vger.kernel.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, virtualization@lists.linux.dev, Joel Granados X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=3574; i=joel.granados@kernel.org; h=from:subject:message-id; bh=gFPfNAZb5Emut5tl59jtS1GCSawh67g0IOaptPFibj4=; b=owJ4nAHtARL+kA0DAAoBupfNUreWQU8ByyZiAGpUxwZskgenDOU98txc57mfzp9zCAPadshX1 w9t16Ag3hXFGYkBswQAAQoAHRYhBK5HCVcl5jElzssnkLqXzVK3lkFPBQJqVMcGAAoJELqXzVK3 lkFPFuML/RuQe3IepvdaZwOqXPTFSxjiaQ9bHG5EjMlqTZJymTxUXke4CX6cffYqR8LOCXv/zqI Xz6yMTCeEaKdC/KbKlarrXHYnX0dUo/F3SqzxbWAoouVQN77rnoI7iQbY+TDK0GEy2zZONsm95u Vf+EfOQeGZuxwgpbCYUR8IBhhpqcVfuF0vI8vaxi7bhmmK30aRoBtLG+WYyHIgf/N7CXmGwRFxC yDHVArNMtiBNObUr0CVTFLxn8/BXuAIVrsNttsPGQm6aDvm3AQd87+wUS2otzOefZp82bJUl73e IzkI9JlAq/XN9dgNUEPdpolmegObR57+ikTaZzNrILLpVchdIIKBR4cZfPkGGVcjwBnrXrvM9Zy kksDs+AIzzP/SDuNq8GseNIMT37Jo/NFsSdfK+eblk8DVjuKx+gEwV7GHjkzZkGe6PEWWgIhT8f uCYW4EEdIC4+bpgG8ygVgbaTDyA1+W81V10LuKN5vBvLR6iuqzESCQGH1rg5ryeHGO+tKQvK3f8 Ig= X-Developer-Key: i=joel.granados@kernel.org; a=openpgp; fpr=F1F8E46D30F0F6C4A45FF4465895FAAC338C6E77 X-Endpoint-Received: by B4 Relay for joel.granados@kernel.org/default with auth_id=239 Replace the warning and file permission change with an error when an "unsafe" net sysctl registration is detected. One of the barriers preventing the const qualification of the ctl_tables in the net directory is the permission (->mode) change in ensure_safe_net_sysctl. This prep commit removes that barrier and ensures that the received ctl_table pointer to the net ctl_table register function is const. Signed-off-by: Joel Granados --- include/net/net_namespace.h | 4 ++-- net/sysctl_net.c | 24 ++++++++++++------------ 2 files changed, 14 insertions(+), 14 deletions(-) diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h index 80de5e98a66d6c9273aa7c5b9d489b22cef8559a..dca0ec809483bec604f4ca3d99dfea32834af8fa 100644 --- a/include/net/net_namespace.h +++ b/include/net/net_namespace.h @@ -522,12 +522,12 @@ struct ctl_table; #ifdef CONFIG_SYSCTL int net_sysctl_init(void); struct ctl_table_header *register_net_sysctl_sz(struct net *net, const char *path, - struct ctl_table *table, size_t table_size); + const struct ctl_table *table, size_t table_size); void unregister_net_sysctl_table(struct ctl_table_header *header); #else static inline int net_sysctl_init(void) { return 0; } static inline struct ctl_table_header *register_net_sysctl_sz(struct net *net, - const char *path, struct ctl_table *table, size_t table_size) + const char *path, const struct ctl_table *table, size_t table_size) { return NULL; } diff --git a/net/sysctl_net.c b/net/sysctl_net.c index 19e8048241bacb18de853d3b904d0f97fd2fe78a..4714887113d90a191c300c9c49a6317d5609efeb 100644 --- a/net/sysctl_net.c +++ b/net/sysctl_net.c @@ -114,16 +114,16 @@ __init int net_sysctl_init(void) goto out; } -/* Verify that sysctls for non-init netns are safe by either: +/* Return error when sysctls for non-init netns are unsafe by verifying: * 1) being read-only, or * 2) having a data pointer which points outside of the global kernel/module * data segment, and rather into the heap where a per-net object was * allocated. */ -static void ensure_safe_net_sysctl(struct net *net, const char *path, - struct ctl_table *table, size_t table_size) +static int ensure_safe_net_sysctl(struct net *net, const char *path, + const struct ctl_table *table, size_t table_size) { - struct ctl_table *ent; + const struct ctl_table *ent; pr_debug("Registering net sysctl (net %p): %s\n", net, path); ent = table; @@ -149,24 +149,24 @@ static void ensure_safe_net_sysctl(struct net *net, const char *path, else continue; - /* If it is writable and points to kernel/module global - * data, then it's probably a netns leak. - */ + /* Warn on netns leak. */ WARN(1, "sysctl %s/%s: data points to %s global data: %ps\n", - path, ent->procname, where, ent->data); + path, ent->procname, where, ent->data); - /* Make it "safe" by dropping writable perms */ - ent->mode &= ~0222; + return -EACCES; } + + return 0; } struct ctl_table_header *register_net_sysctl_sz(struct net *net, const char *path, - struct ctl_table *table, + const struct ctl_table *table, size_t table_size) { if (!net_eq(net, &init_net)) - ensure_safe_net_sysctl(net, path, table, table_size); + if (ensure_safe_net_sysctl(net, path, table, table_size)) + return NULL; return __register_sysctl_table(&net->sysctls, path, table, table_size); } -- 2.50.1