Re: [PATCH v2 net-next] net: hsr: fix suspicious usage in hsr_node_get_first()
From: Eric Dumazet <hidden>
Date: 2022-02-10 17:47:50
On 2/10/22 08:23, Juhee Kang wrote:
Currently, to dereference hlist_node which is result of hlist_first_rcu(),
rcu_dereference() is used. But, suspicious RCU warnings occur because
the caller doesn't acquire RCU. So it was solved by adding rcu_read_lock().
The kernel test robot reports:
[ 53.750001][ T3597] =============================
[ 53.754849][ T3597] WARNING: suspicious RCU usage
[ 53.759833][ T3597] 5.17.0-rc2-syzkaller-00903-g45230829827b #0 Not tainted
[ 53.766947][ T3597] -----------------------------
[ 53.771840][ T3597] net/hsr/hsr_framereg.c:34 suspicious rcu_dereference_check() usage!
[ 53.780129][ T3597] other info that might help us debug this:
[ 53.790594][ T3597] rcu_scheduler_active = 2, debug_locks = 1
[ 53.798896][ T3597] 2 locks held by syz-executor.0/3597:Please include whole stack.
quoted hunk ↗ jump to hunk
Fixes: 4acc45db7115 ("net: hsr: use hlist_head instead of list_head for mac addresses") Reported-by: Eric Dumazet <redacted> Reported-by: syzbot+f0eb4f3876de066b128c@syzkaller.appspotmail.com Signed-off-by: Juhee Kang <redacted> --- v2: - rebase current net-next tree net/hsr/hsr_framereg.c | 3 +++ 1 file changed, 3 insertions(+)diff --git a/net/hsr/hsr_framereg.c b/net/hsr/hsr_framereg.c index b3c6ffa1894d..92abdf855327 100644 --- a/net/hsr/hsr_framereg.c +++ b/net/hsr/hsr_framereg.c@@ -31,7 +31,10 @@ struct hsr_node *hsr_node_get_first(struct hlist_head *head) { struct hlist_node *first; + rcu_read_lock(); first = rcu_dereference(hlist_first_rcu(head)); + rcu_read_unlock(); + if (first) return hlist_entry(first, struct hsr_node, mac_list);
This is not fixing anything, just silence the warning.