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Subject[PATCH 5.4 135/178] kprobes: Suppress the suspicious RCU warning on kprobes
From: Masami Hiramatsu <>

[ Upstream commit 6743ad432ec92e680cd0d9db86cb17b949cf5a43 ]

Anders reported that the lockdep warns that suspicious
RCU list usage in register_kprobe() (detected by
CONFIG_PROVE_RCU_LIST.) This is because get_kprobe()
access kprobe_table[] by hlist_for_each_entry_rcu()
without rcu_read_lock.

If we call get_kprobe() from the breakpoint handler context,
it is run with preempt disabled, so this is not a problem.
But in other cases, instead of rcu_read_lock(), we locks
kprobe_mutex so that the kprobe_table[] is not updated.
So, current code is safe, but still not good from the view
point of RCU.

Joel suggested that we can silent that warning by passing
lockdep_is_held() to the last argument of

Add lockdep_is_held(&kprobe_mutex) at the end of the
hlist_for_each_entry_rcu() to suppress the warning.


Reported-by: Anders Roxell <>
Suggested-by: Joel Fernandes <>
Reviewed-by: Joel Fernandes (Google) <>
Signed-off-by: Masami Hiramatsu <>
Signed-off-by: Steven Rostedt (VMware) <>
Signed-off-by: Sasha Levin <>
kernel/kprobes.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 195ecb955fcc5..950a5cfd262ce 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -326,7 +326,8 @@ struct kprobe *get_kprobe(void *addr)
struct kprobe *p;

head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
- hlist_for_each_entry_rcu(p, head, hlist) {
+ hlist_for_each_entry_rcu(p, head, hlist,
+ lockdep_is_held(&kprobe_mutex)) {
if (p->addr == addr)
return p;
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