Re: [PATCH] tracing: fprobe: fix suspicious rcu usage in fprobe_entry
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: 2025-09-02 09:17:18
Also in:
lkml
Menglong Dong [off-list ref] wrote:
quoted hunk ↗ jump to hunk
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index fb127fa95f21..fece0f849c1c 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c@@ -269,7 +269,9 @@ static int fprobe_entry(struct ftrace_graph_ent *trace, struct fgraph_ops *gops, if (WARN_ON_ONCE(!fregs)) return 0; + rcu_read_lock(); head = rhltable_lookup(&fprobe_ip_table, &func, fprobe_rht_params); + rcu_read_unlock(); reserved_words = 0; rhl_for_each_entry_rcu(node, pos, head, hlist) { if (node->addr != func)
Actually this isn't quite right. I know that it is a false-positive so that it's actually safe, but if you're going to mark it with rcu_read_lock, it should cover both the lookup as well as the dereference which happens in the loop rhl_for_each_entry_rcu. Thanks, -- Email: Herbert Xu [off-list ref] Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt