From 649027b56ff24abaac5066a9f2ac7f86c09f357e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marcin=20Wcis=C5=82o?= Date: Sun, 16 Feb 2025 02:53:08 +0100 Subject: [PATCH 1/2] net/sched: sch_hfsc: Ensure inner classes have fsc curve MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit jira VULN-6713 cve CVE-2023-4623 commit-author Budimir Markovic commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f HFSC assumes that inner classes have an fsc curve, but it is currently possible for classes without an fsc curve to become parents. This leads to bugs including a use-after-free. Don't allow non-root classes without HFSC_FSC to become parents. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Budimir Markovic Signed-off-by: Budimir Markovic Acked-by: Jamal Hadi Salim Link: https://lore.kernel.org/r/20230824084905.422-1-markovicbudimir@gmail.com Signed-off-by: Jakub Kicinski (cherry picked from commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f) Signed-off-by: Marcin Wcisło --- net/sched/sch_hfsc.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c index d3979a6000e7d..17ddf314f4e81 100644 --- a/net/sched/sch_hfsc.c +++ b/net/sched/sch_hfsc.c @@ -1012,6 +1012,10 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid, if (parent == NULL) return -ENOENT; } + if (!(parent->cl_flags & HFSC_FSC) && parent != &q->root) { + NL_SET_ERR_MSG(extack, "Invalid parent - parent class must have FSC"); + return -EINVAL; + } if (classid == 0 || TC_H_MAJ(classid ^ sch->handle) != 0) return -EINVAL; From bea021ed918669a5054834eddb5fa4847b62c1fe Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marcin=20Wcis=C5=82o?= Date: Wed, 19 Feb 2025 02:50:19 +0100 Subject: [PATCH 2/2] net/sched: sch_hfsc: upgrade 'rt' to 'sc' when it becomes a inner curve MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit jira VULN-6713 cve CVE-2023-4623 commit-author Pedro Tammela commit a13b67c9a015c4e21601ef9aa4ec9c5d972df1b4 Christian Theune says: I upgraded from 6.1.38 to 6.1.55 this morning and it broke my traffic shaping script, leaving me with a non-functional uplink on a remote router. A 'rt' curve cannot be used as a inner curve (parent class), but we were allowing such configurations since the qdisc was introduced. Such configurations would trigger a UAF as Budimir explains: The parent will have vttree_insert() called on it in init_vf(), but will not have vttree_remove() called on it in update_vf() because it does not have the HFSC_FSC flag set. The qdisc always assumes that inner classes have the HFSC_FSC flag set. This is by design as it doesn't make sense 'qdisc wise' for an 'rt' curve to be an inner curve. Budimir's original patch disallows users to add classes with a 'rt' parent, but this is too strict as it breaks users that have been using 'rt' as a inner class. Another approach, taken by this patch, is to upgrade the inner 'rt' into a 'sc', warning the user in the process. It avoids the UAF reported by Budimir while also being more permissive to bad scripts/users/code using 'rt' as a inner class. Users checking the `tc class ls [...]` or `tc class get [...]` dumps would observe the curve change and are potentially breaking with this change. v1->v2: https://lore.kernel.org/all/20231013151057.2611860-1-pctammela@mojatatu.com/ - Correct 'Fixes' tag and merge with revert (Jakub) Cc: Christian Theune Cc: Budimir Markovic Fixes: b3d26c5702c7 ("net/sched: sch_hfsc: Ensure inner classes have fsc curve") Signed-off-by: Pedro Tammela Acked-by: Jamal Hadi Salim Link: https://lore.kernel.org/r/20231017143602.3191556-1-pctammela@mojatatu.com Signed-off-by: Jakub Kicinski (cherry picked from commit a13b67c9a015c4e21601ef9aa4ec9c5d972df1b4) Signed-off-by: Marcin Wcisło --- net/sched/sch_hfsc.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c index 17ddf314f4e81..d0241990875e1 100644 --- a/net/sched/sch_hfsc.c +++ b/net/sched/sch_hfsc.c @@ -903,6 +903,14 @@ hfsc_change_usc(struct hfsc_class *cl, struct tc_service_curve *usc, cl->cl_flags |= HFSC_USC; } +static void +hfsc_upgrade_rt(struct hfsc_class *cl) +{ + cl->cl_fsc = cl->cl_rsc; + rtsc_init(&cl->cl_virtual, &cl->cl_fsc, cl->cl_vt, cl->cl_total); + cl->cl_flags |= HFSC_FSC; +} + static const struct nla_policy hfsc_policy[TCA_HFSC_MAX + 1] = { [TCA_HFSC_RSC] = { .len = sizeof(struct tc_service_curve) }, [TCA_HFSC_FSC] = { .len = sizeof(struct tc_service_curve) }, @@ -1012,10 +1020,6 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid, if (parent == NULL) return -ENOENT; } - if (!(parent->cl_flags & HFSC_FSC) && parent != &q->root) { - NL_SET_ERR_MSG(extack, "Invalid parent - parent class must have FSC"); - return -EINVAL; - } if (classid == 0 || TC_H_MAJ(classid ^ sch->handle) != 0) return -EINVAL; @@ -1066,6 +1070,12 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid, cl->cf_tree = RB_ROOT; sch_tree_lock(sch); + /* Check if the inner class is a misconfigured 'rt' */ + if (!(parent->cl_flags & HFSC_FSC) && parent != &q->root) { + NL_SET_ERR_MSG(extack, + "Forced curve change on parent 'rt' to 'sc'"); + hfsc_upgrade_rt(parent); + } qdisc_class_hash_insert(&q->clhash, &cl->cl_common); list_add_tail(&cl->siblings, &parent->children); if (parent->level == 0)