linux-kernel - [PATCH 2/3] static_call: Fix static_call_text_reserved() vs _

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Message-ID: <20210628113045.106211657@infradead.org>
Date:   Mon, 28 Jun 2021 13:24:11 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     jpoimboe@...hat.com, jbaron@...mai.com, rostedt@...dmis.org,
        ardb@...nel.org, naveen.n.rao@...ux.ibm.com,
        anil.s.keshavamurthy@...el.com, mhiramat@...nel.org,
        davem@...emloft.net
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: [PATCH 2/3] static_call: Fix static_call_text_reserved() vs __init

It turns out that static_call_text_reserved() was reporting __init
text as being reserved past the time when the __init text was freed
and re-used.

This is mostly harmless and will at worst result in refusing a kprobe.

Fixes: 6333e8f73b83 ("static_call: Avoid kprobes on inline static_call()s")
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/static_call.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -292,13 +292,15 @@ static int addr_conflict(struct static_c
 
 static int __static_call_text_reserved(struct static_call_site *iter_start,
 				       struct static_call_site *iter_stop,
-				       void *start, void *end)
+				       void *start, void *end, bool init)
 {
 	struct static_call_site *iter = iter_start;
 
 	while (iter < iter_stop) {
-		if (addr_conflict(iter, start, end))
-			return 1;
+		if (init || !static_call_is_init(iter)) {
+			if (addr_conflict(iter, start, end))
+				return 1;
+		}
 		iter++;
 	}
 
@@ -324,7 +326,7 @@ static int __static_call_mod_text_reserv
 
 	ret = __static_call_text_reserved(mod->static_call_sites,
 			mod->static_call_sites + mod->num_static_call_sites,
-			start, end);
+			start, end, mod->state == MODULE_STATE_COMING);
 
 	module_put(mod);
 
@@ -459,8 +461,9 @@ static inline int __static_call_mod_text
 
 int static_call_text_reserved(void *start, void *end)
 {
+	bool init = system_state < SYSTEM_RUNNING;
 	int ret = __static_call_text_reserved(__start_static_call_sites,
-			__stop_static_call_sites, start, end);
+			__stop_static_call_sites, start, end, init);
 
 	if (ret)
 		return ret;