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authorMasami Hiramatsu <mhiramat@kernel.org>2020-05-12 17:02:33 +0900
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2020-06-16 21:21:01 -0400
commit6743ad432ec92e680cd0d9db86cb17b949cf5a43 (patch)
treeaba82276d117d68f61e22d309199040cc889454d /kernel
parent4ef57b21d6fb49d2b25c47e4cff467a0c2c8b6b7 (diff)
kprobes: Suppress the suspicious RCU warning on kprobes
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 hlist_for_each_entry_rcu(). Add lockdep_is_held(&kprobe_mutex) at the end of the hlist_for_each_entry_rcu() to suppress the warning. Link: http://lkml.kernel.org/r/158927055350.27680.10261450713467997503.stgit@devnote2 Reported-by: Anders Roxell <anders.roxell@linaro.org> Suggested-by: Joel Fernandes <joel@joelfernandes.org> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/kprobes.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 50cd84f53df0..8b2fd4145ab3 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;
}