When CONFIG_PROVE_RCU_LIST is enabled, fprobe triggers the following
warning:
WARNING: suspicious RCU usage
kernel/trace/fprobe.c:457 RCU-list traversed in non-reader section!!
other info that might help us debug this:
#1: ffffffff863c4e08 (fprobe_mutex){+.+.}-{4:4}, at:
fprobe_module_callback+0x7b/0x8c0
Call Trace:
fprobe_module_callback
notifier_call_chain
blocking_notifier_call_chain
This warning occurs because fprobe_remove_node_in_module() traverses an
RCU list using RCU primitives without holding an RCU read lock. However,
the function is only called from fprobe_module_callback(), which holds
the fprobe_mutex lock that provides sufficient protection for safely
traversing the list.
Fix the warning by specifying the locking design to the
CONFIG_PROVE_RCU_LIST mechanism. Add the lockdep_is_held() argument to
hlist_for_each_entry_rcu() to inform the RCU checker that fprobe_mutex
provides the required protection.
Fixes: a3dc2983ca7b90 ("tracing: fprobe: Cleanup fprobe hash when module
unloading")
Signed-off-by: Breno Leitao <[email protected]>
---
kernel/trace/fprobe.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 95c6e3473a76b..ba7ff14f5339b 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -454,7 +454,8 @@ static void fprobe_remove_node_in_module(struct module
*mod, struct hlist_head *
struct fprobe_hlist_node *node;
int ret = 0;
- hlist_for_each_entry_rcu(node, head, hlist) {
+ hlist_for_each_entry_rcu(node, head, hlist,
+ lockdep_is_held(&fprobe_mutex)) {
if (!within_module(node->addr, mod))
continue;
if (delete_fprobe_node(node))
---
base-commit: 3b07108ada81a8ebcebf1fe61367b4e436c895bd
change-id: 20250410-fprobe-dfe91798f03c
Best regards,
--
Breno Leitao <[email protected]>
