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 6BD141FCFE2; Mon, 2 Jun 2025 14:36:09 +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=1748874969; cv=none; b=YAC3LB9A3jfNWsKoxzXivG4bMlD1VcjZrPPR8sdD5i9hh+Ep3nEyxQ8+fOuSpgHdY5lQXH37LKz1bysIamzSz18qFw5t8Z3ZmTfU/BdqlugOp/xRC6JuH8vIw5dBvdIcSzwXquH8sPpwsRB4m7SjMq6/z0vHL8Pvh4aQUfu2MZM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748874969; c=relaxed/simple; bh=Scj1jNnUhTOcS8NZupQqRSQ0da6+/k+1zneoPSqZ5CI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YSEE6qhxZejuDn+6sgMcbFLCD0ooEMvuhBPUQaMeMG1OB1wymsM6jY3B5EdyiR5Xw7ZoT3hactZKhAmuTpD6Jiz23+aMUse1+zsTv+FQX2VFiU0ZNDmYyR33O6YXGMJGFm4U2iSywAulfepqQN8VfZl6nzQ4G6qBrZO114nO2YA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0k/KGCR4; 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="0k/KGCR4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 942C6C4CEEB; Mon, 2 Jun 2025 14:36:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1748874968; bh=Scj1jNnUhTOcS8NZupQqRSQ0da6+/k+1zneoPSqZ5CI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0k/KGCR4KvZxOrBFEC0ut66btjOCq7L9fghQNbZgqq8P5rgygB8BwE/woHHrjF/IV MVbjuhTTnplxQlCf4xS6jOHwoUBDjEfF+chW2wP5sIV4CUWNlw6YNLswueh7tMo0fh bRWLFJGqYgkLWKc9Lr3pEHYAI6okowYmOBfzg7jw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Savino Dicanosa , William Liu , Jamal Hadi Salim , Victor Nogueira , Pedro Tammela , Paolo Abeni Subject: [PATCH 5.4 191/204] net_sched: hfsc: Address reentrant enqueue adding class to eltree twice Date: Mon, 2 Jun 2025 15:48:44 +0200 Message-ID: <20250602134303.183783087@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250602134255.449974357@linuxfoundation.org> References: <20250602134255.449974357@linuxfoundation.org> User-Agent: quilt/0.68 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 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pedro Tammela commit ac9fe7dd8e730a103ae4481147395cc73492d786 upstream. Savino says: "We are writing to report that this recent patch (141d34391abbb315d68556b7c67ad97885407547) [1] can be bypassed, and a UAF can still occur when HFSC is utilized with NETEM. The patch only checks the cl->cl_nactive field to determine whether it is the first insertion or not [2], but this field is only incremented by init_vf [3]. By using HFSC_RSC (which uses init_ed) [4], it is possible to bypass the check and insert the class twice in the eltree. Under normal conditions, this would lead to an infinite loop in hfsc_dequeue for the reasons we already explained in this report [5]. However, if TBF is added as root qdisc and it is configured with a very low rate, it can be utilized to prevent packets from being dequeued. This behavior can be exploited to perform subsequent insertions in the HFSC eltree and cause a UAF." To fix both the UAF and the infinite loop, with netem as an hfsc child, check explicitly in hfsc_enqueue whether the class is already in the eltree whenever the HFSC_RSC flag is set. [1] https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=141d34391abbb315d68556b7c67ad97885407547 [2] https://elixir.bootlin.com/linux/v6.15-rc5/source/net/sched/sch_hfsc.c#L1572 [3] https://elixir.bootlin.com/linux/v6.15-rc5/source/net/sched/sch_hfsc.c#L677 [4] https://elixir.bootlin.com/linux/v6.15-rc5/source/net/sched/sch_hfsc.c#L1574 [5] https://lore.kernel.org/netdev/8DuRWwfqjoRDLDmBMlIfbrsZg9Gx50DHJc1ilxsEBNe2D6NMoigR_eIRIG0LOjMc3r10nUUZtArXx4oZBIdUfZQrwjcQhdinnMis_0G7VEk=@willsroot.io/T/#u Fixes: 37d9cf1a3ce3 ("sched: Fix detection of empty queues in child qdiscs") Reported-by: Savino Dicanosa Reported-by: William Liu Acked-by: Jamal Hadi Salim Tested-by: Victor Nogueira Signed-off-by: Pedro Tammela Link: https://patch.msgid.link/20250522181448.1439717-2-pctammela@mojatatu.com Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman --- net/sched/sch_hfsc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/net/sched/sch_hfsc.c +++ b/net/sched/sch_hfsc.c @@ -176,6 +176,11 @@ struct hfsc_sched { #define HT_INFINITY 0xffffffffffffffffULL /* infinite time value */ +static bool cl_in_el_or_vttree(struct hfsc_class *cl) +{ + return ((cl->cl_flags & HFSC_FSC) && cl->cl_nactive) || + ((cl->cl_flags & HFSC_RSC) && !RB_EMPTY_NODE(&cl->el_node)); +} /* * eligible tree holds backlogged classes being sorted by their eligible times. @@ -1038,6 +1043,8 @@ hfsc_change_class(struct Qdisc *sch, u32 if (cl == NULL) return -ENOBUFS; + RB_CLEAR_NODE(&cl->el_node); + err = tcf_block_get(&cl->block, &cl->filter_list, sch, extack); if (err) { kfree(cl); @@ -1576,7 +1583,7 @@ hfsc_enqueue(struct sk_buff *skb, struct sch->qstats.backlog += len; sch->q.qlen++; - if (first && !cl->cl_nactive) { + if (first && !cl_in_el_or_vttree(cl)) { if (cl->cl_flags & HFSC_RSC) init_ed(cl, len); if (cl->cl_flags & HFSC_FSC)