6.14-stable review patch. If anyone has any objections, please let me know.
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From: Breno Leitao leitao@debian.org
[ Upstream commit 9dda18a32b4a6693fccd3f7c0738af646147b1cf ]
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.
Link: https://lore.kernel.org/all/20250410-fprobe-v1-1-068ef5f41436@debian.org/
Fixes: a3dc2983ca7b90 ("tracing: fprobe: Cleanup fprobe hash when module unloading") Signed-off-by: Breno Leitao leitao@debian.org Tested-by: Antonio Quartulli antonio@mandelbit.com Tested-by: Matthieu Baerts (NGI0) matttbe@kernel.org Signed-off-by: Masami Hiramatsu (Google) mhiramat@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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))