From: Aldo Ariel Panzardo <qwe.aldo@gmail.com> stable inclusion from stable-v6.6.153 commit 4131dd0b6f67acddd616ed7c244e1d3eedd46e7b category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16947 CVE: CVE-2026-68138 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit f43ee0c0730d6191629b5ee1ceae27b1ebfdc047 ] qdisc_get_rtab() and qdisc_put_rtab() mutate the process-global singly linked list qdisc_rtab_list and a plain non-atomic 'int refcnt' with no lock. This was only safe because every caller historically held the RTNL mutex, which serialized all rate-table lookups, inserts and frees. That invariant no longer holds. cls_flower sets TCF_PROTO_OPS_DOIT_UNLOCKED, so tc_new_tfilter() keeps rtnl_held == false for it and sets TCA_ACT_FLAGS_NO_RTNL. That flag propagates through tcf_exts_validate_ex() -> tcf_action_init() -> tcf_action_init_1() -> tcf_police_init(), which calls qdisc_get_rtab()/qdisc_put_rtab() with the RTNL mutex NOT held. Two RTM_NEWTFILTER requests on different CPUs, each adding a flower filter with a police action carrying the same rate, then race on qdisc_rtab_list and on the non-atomic refcnt, leading to a use-after-free / double-free of the kmalloc-2k struct qdisc_rate_table. qdisc_rtab_list is a single global (not per-netns), so the corrupted object is shared system-wide. BUG: KASAN: slab-use-after-free in qdisc_put_rtab+0x12f/0x160 qdisc_put_rtab+0x12f/0x160 tcf_police_init+0xda9/0x1590 tcf_action_init_1+0x460/0x6b0 tcf_action_init+0x439/0xa40 tcf_exts_validate_ex+0x42d/0x550 fl_change+0xddd/0x7da0 tc_new_tfilter+0xaa7/0x2420 rtnetlink_rcv_msg+0x95e/0xe90 which belongs to the cache kmalloc-2k of size 2048 Protect qdisc_rtab_list and the refcount with a dedicated spinlock. The (sleeping, GFP_KERNEL) allocation in qdisc_get_rtab() is performed before taking the lock; if a concurrent inserter added an identical table in the meantime the freshly allocated one is freed under the lock, so no duplicate is leaked. qdisc_put_rtab() now decrements the refcount and unlinks under the same lock. Fixes: 470502de5bdb ("net: sched: unlock rules update API") Suggested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@gmail.com> Cc: stable@vger.kernel.org Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/20260715114114.446841-1-qwe.aldo@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- net/sched/sch_api.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index ff7bad762496..3f5db8d378a8 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -411,33 +411,39 @@ static __u8 __detect_linklayer(struct tc_ratespec *r, __u32 *rtab) } return TC_LINKLAYER_ETHERNET; } static struct qdisc_rate_table *qdisc_rtab_list; +static DEFINE_SPINLOCK(qdisc_rtab_lock); struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r, struct nlattr *tab, struct netlink_ext_ack *extack) { - struct qdisc_rate_table *rtab; + struct qdisc_rate_table *rtab, *new_rtab; if (tab == NULL || r->rate == 0 || r->cell_log == 0 || r->cell_log >= 32 || nla_len(tab) != TC_RTAB_SIZE) { NL_SET_ERR_MSG(extack, "Invalid rate table parameters for searching"); return NULL; } + new_rtab = kmalloc(sizeof(*new_rtab), GFP_KERNEL); + + spin_lock(&qdisc_rtab_lock); for (rtab = qdisc_rtab_list; rtab; rtab = rtab->next) { if (!memcmp(&rtab->rate, r, sizeof(struct tc_ratespec)) && !memcmp(&rtab->data, nla_data(tab), 1024)) { rtab->refcnt++; + spin_unlock(&qdisc_rtab_lock); + kfree(new_rtab); return rtab; } } - rtab = kmalloc(sizeof(*rtab), GFP_KERNEL); + rtab = new_rtab; if (rtab) { rtab->rate = *r; rtab->refcnt = 1; memcpy(rtab->data, nla_data(tab), 1024); if (r->linklayer == TC_LINKLAYER_UNAWARE) @@ -445,30 +451,38 @@ struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r, rtab->next = qdisc_rtab_list; qdisc_rtab_list = rtab; } else { NL_SET_ERR_MSG(extack, "Failed to allocate new qdisc rate table"); } + spin_unlock(&qdisc_rtab_lock); return rtab; } EXPORT_SYMBOL(qdisc_get_rtab); void qdisc_put_rtab(struct qdisc_rate_table *tab) { struct qdisc_rate_table *rtab, **rtabp; - if (!tab || --tab->refcnt) + if (!tab) return; + spin_lock(&qdisc_rtab_lock); + if (--tab->refcnt) { + spin_unlock(&qdisc_rtab_lock); + return; + } + for (rtabp = &qdisc_rtab_list; (rtab = *rtabp) != NULL; rtabp = &rtab->next) { if (rtab == tab) { *rtabp = rtab->next; - kfree(rtab); - return; + break; } } + spin_unlock(&qdisc_rtab_lock); + kfree(tab); } EXPORT_SYMBOL(qdisc_put_rtab); static LIST_HEAD(qdisc_stab_list); -- 2.43.0