From d4d305e149f5d844567a1d43b41277c7de3f91b6 Mon Sep 17 00:00:00 2001 From: Victor Nogueira Date: Thu, 14 Aug 2025 21:11:02 +0800 Subject: [PATCH 1/3] net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc mainline inclusion from mainline-v6.15-rc5 commit 141d34391abbb315d68556b7c67ad97885407547 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IC8Y28 CVE: CVE-2025-37890 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=141d34391abbb315d68556b7c67ad97885407547 -------------------------------- As described in Gerrard's report [1], we have a UAF case when an hfsc class has a netem child qdisc. The crux of the issue is that hfsc is assuming that checking for cl->qdisc->q.qlen == 0 guarantees that it hasn't inserted the class in the vttree or eltree (which is not true for the netem duplicate case). This patch checks the n_active class variable to make sure that the code won't insert the class in the vttree or eltree twice, catering for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/ Fixes: 37d9cf1a3ce3 ("sched: Fix detection of empty queues in child qdiscs") Reported-by: Gerrard Tai Acked-by: Jamal Hadi Salim Signed-off-by: Victor Nogueira Link: https://patch.msgid.link/20250425220710.3964791-3-victor@mojatatu.com Signed-off-by: Jakub Kicinski Signed-off-by: Dong Chenchen --- net/sched/sch_hfsc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c index f0075e42df3f..7daaffe9df68 100644 --- a/net/sched/sch_hfsc.c +++ b/net/sched/sch_hfsc.c @@ -1566,7 +1566,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) return err; } - if (first) { + if (first && !cl->cl_nactive) { if (cl->cl_flags & HFSC_RSC) init_ed(cl, len); if (cl->cl_flags & HFSC_FSC) -- Gitee From 4c57c3b35236e3a1d6067442b085e5505e6296c9 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Thu, 14 Aug 2025 21:11:03 +0800 Subject: [PATCH 2/3] sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() mainline inclusion from mainline-v6.15-rc6 commit 3f981138109f63232a5fb7165938d4c945cc1b9d category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IC8Y28 CVE: CVE-2025-37890 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3f981138109f63232a5fb7165938d4c945cc1b9d -------------------------------- When enqueuing the first packet to an HFSC class, hfsc_enqueue() calls the child qdisc's peek() operation before incrementing sch->q.qlen and sch->qstats.backlog. If the child qdisc uses qdisc_peek_dequeued(), this may trigger an immediate dequeue and potential packet drop. In such cases, qdisc_tree_reduce_backlog() is called, but the HFSC qdisc's qlen and backlog have not yet been updated, leading to inconsistent queue accounting. This can leave an empty HFSC class in the active list, causing further consequences like use-after-free. This patch fixes the bug by moving the increment of sch->q.qlen and sch->qstats.backlog before the call to the child qdisc's peek() operation. This ensures that queue length and backlog are always accurate when packet drops or dequeues are triggered during the peek. Fixes: 12d0ad3be9c3 ("net/sched/sch_hfsc.c: handle corner cases where head may change invalidating calculated deadline") Reported-by: Mingi Cho Signed-off-by: Cong Wang Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250518222038.58538-2-xiyou.wangcong@gmail.com Reviewed-by: Jamal Hadi Salim Signed-off-by: Paolo Abeni Signed-off-by: Dong Chenchen --- net/sched/sch_hfsc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c index 7daaffe9df68..6f6fd2bbd949 100644 --- a/net/sched/sch_hfsc.c +++ b/net/sched/sch_hfsc.c @@ -1566,6 +1566,9 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) return err; } + sch->qstats.backlog += len; + sch->q.qlen++; + if (first && !cl->cl_nactive) { if (cl->cl_flags & HFSC_RSC) init_ed(cl, len); @@ -1581,9 +1584,6 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) } - sch->qstats.backlog += len; - sch->q.qlen++; - return NET_XMIT_SUCCESS; } -- Gitee From 9c6109068e599c4ae26d391ab8f11d13000e10a1 Mon Sep 17 00:00:00 2001 From: Pedro Tammela Date: Thu, 14 Aug 2025 21:11:04 +0800 Subject: [PATCH 3/3] net_sched: hfsc: Address reentrant enqueue adding class to eltree twice mainline inclusion from mainline-v6.15-rc7 commit ac9fe7dd8e730a103ae4481147395cc73492d786 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IC8Y28 CVE: CVE-2025-37890 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ac9fe7dd8e730a103ae4481147395cc73492d786 -------------------------------- 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: Dong Chenchen --- net/sched/sch_hfsc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c index 6f6fd2bbd949..69d75bbfc20f 100644 --- 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. @@ -1033,6 +1038,8 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid, 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); @@ -1569,7 +1576,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) 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) -- Gitee