From: Charalampos Mitrodimas Date: Wed, 11 Jun 2025 17:20:43 +0000 (+0000) Subject: net, bpf: Fix RCU usage in task_cls_state() for BPF programs X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7f12c33850482521c961c5c15a50ebe9b9a88d1e;p=thirdparty%2Flinux.git net, bpf: Fix RCU usage in task_cls_state() for BPF programs The commit ee971630f20f ("bpf: Allow some trace helpers for all prog types") made bpf_get_cgroup_classid_curr helper available to all BPF program types, not just networking programs. This helper calls __task_get_classid() which internally calls task_cls_state() requiring rcu_read_lock_bh_held(). This works in networking/tc context where RCU BH is held, but triggers an RCU warning when called from other contexts like BPF syscall programs that run under rcu_read_lock_trace(): WARNING: suspicious RCU usage 6.15.0-rc4-syzkaller-g079e5c56a5c4 #0 Not tainted ----------------------------- net/core/netclassid_cgroup.c:24 suspicious rcu_dereference_check() usage! Fix this by also accepting rcu_read_lock_held() and rcu_read_lock_trace_held() as valid RCU contexts in the task_cls_state() function. This ensures the helper works correctly in all needed RCU contexts where it might be called, regular RCU, RCU BH (for networking), and RCU trace (for BPF syscall programs). Fixes: ee971630f20f ("bpf: Allow some trace helpers for all prog types") Reported-by: syzbot+b4169a1cfb945d2ed0ec@syzkaller.appspotmail.com Signed-off-by: Charalampos Mitrodimas Signed-off-by: Daniel Borkmann Acked-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20250611-rcu-fix-task_cls_state-v3-1-3d30e1de753f@posteo.net Closes: https://syzkaller.appspot.com/bug?extid=b4169a1cfb945d2ed0ec --- diff --git a/net/core/netclassid_cgroup.c b/net/core/netclassid_cgroup.c index d22f0919821e9..dff66d8fb325d 100644 --- a/net/core/netclassid_cgroup.c +++ b/net/core/netclassid_cgroup.c @@ -21,7 +21,9 @@ static inline struct cgroup_cls_state *css_cls_state(struct cgroup_subsys_state struct cgroup_cls_state *task_cls_state(struct task_struct *p) { return css_cls_state(task_css_check(p, net_cls_cgrp_id, - rcu_read_lock_bh_held())); + rcu_read_lock_held() || + rcu_read_lock_bh_held() || + rcu_read_lock_trace_held())); } EXPORT_SYMBOL_GPL(task_cls_state);