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 D9E702FF144; Wed, 8 Apr 2026 18:29:57 +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=1775672997; cv=none; b=kXbeYpHxJfJAlWixdMR5mvqmSFA9NvYLfZzY+7oJqfCq9nSAHpwwcrFURO023ncu5P9ggqyJ7h/pdYBQt9YyT94Aj8uuM9q0o8/BCk1S7r8ChE99k7l292r+UVFJePrAL9opPt0yeMkd4UOW6wJdRo2R/8CN3HnHqtilG65vvgk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775672997; c=relaxed/simple; bh=/SMjH8ERygbfkJYbW/HwKLci+TSpZIwunHPd4amatiU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UEO7YYEtYmoFzCrCmu80OG4RgrXz8bc+8NUJVoEvX85dif5ZEwTjesMQwuGcyv+dWQypq1nHBGKf1xMtdSLUW3/pK6eDr05+tK+mLNLxoGw0nkXi8pAcdNhJOc4hkd827HuSkI3F2RQsPJEIYKcfl1fUZWZXBZ05XzbviRIrJD4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=sEKei2hg; 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="sEKei2hg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70116C19421; Wed, 8 Apr 2026 18:29:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775672997; bh=/SMjH8ERygbfkJYbW/HwKLci+TSpZIwunHPd4amatiU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sEKei2hgYFNg+LnvTzcahTlmbjpqj0+BZKPoC1bAayL3OLKxTJ2R1GAfGDMrLtnL7 RUJGAPqTFg9kxOimhdsIOLw/nk6BOtbEndCwozmwVTVj+ahvkcQYItdKnGfGXTUftf DSbk0aFze8FALClI6OcIwojrUG5a0WsUsNZ608Uc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yifan Wu , Juefei Pu , Yuan Tan , Xin Liu , Ren Wei , Zhengchuan Liang , Ren Wei , Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18 061/277] net: ipv6: flowlabel: defer exclusive option free until RCU teardown Date: Wed, 8 Apr 2026 20:00:46 +0200 Message-ID: <20260408175936.137937216@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175933.836769063@linuxfoundation.org> References: <20260408175933.836769063@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zhengchuan Liang [ Upstream commit 9ca562bb8e66978b53028fa32b1a190708e6a091 ] `ip6fl_seq_show()` walks the global flowlabel hash under the seq-file RCU read-side lock and prints `fl->opt->opt_nflen` when an option block is present. Exclusive flowlabels currently free `fl->opt` as soon as `fl->users` drops to zero in `fl_release()`. However, the surrounding `struct ip6_flowlabel` remains visible in the global hash table until later garbage collection removes it and `fl_free_rcu()` finally tears it down. A concurrent `/proc/net/ip6_flowlabel` reader can therefore race that early `kfree()` and dereference freed option state, triggering a crash in `ip6fl_seq_show()`. Fix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches the lifetime already required for the enclosing flowlabel while readers can still reach it under RCU. Fixes: d3aedd5ebd4b ("ipv6 flowlabel: Convert hash list to RCU.") Reported-by: Yifan Wu Reported-by: Juefei Pu Co-developed-by: Yuan Tan Signed-off-by: Yuan Tan Suggested-by: Xin Liu Tested-by: Ren Wei Signed-off-by: Zhengchuan Liang Signed-off-by: Ren Wei Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/07351f0ec47bcee289576f39f9354f4a64add6e4.1774855883.git.zcliangcn@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv6/ip6_flowlabel.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c index 60d0be47a9f31..8aa29b3d3daca 100644 --- a/net/ipv6/ip6_flowlabel.c +++ b/net/ipv6/ip6_flowlabel.c @@ -133,11 +133,6 @@ static void fl_release(struct ip6_flowlabel *fl) if (time_after(ttd, fl->expires)) fl->expires = ttd; ttd = fl->expires; - if (fl->opt && fl->share == IPV6_FL_S_EXCL) { - struct ipv6_txoptions *opt = fl->opt; - fl->opt = NULL; - kfree(opt); - } if (!timer_pending(&ip6_fl_gc_timer) || time_after(ip6_fl_gc_timer.expires, ttd)) mod_timer(&ip6_fl_gc_timer, ttd); -- 2.53.0