netdev - [PATCH v6 bpf-next 01/14] bpf: fix bpf_put_raw_tracepoint()'s use of __module

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Date:   Thu, 3 Dec 2020 12:46:21 -0800
From:   Andrii Nakryiko <andrii@...nel.org>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>
CC:     <andrii@...nel.org>, <kernel-team@...com>,
        Martin KaFai Lau <kafai@...com>
Subject: [PATCH v6 bpf-next 01/14] bpf: fix bpf_put_raw_tracepoint()'s use of __module_address()

__module_address() needs to be called with preemption disabled or with
module_mutex taken. preempt_disable() is enough for read-only uses, which is
what this fix does. Also, module_put() does internal check for NULL, so drop
it as well.

Fixes: a38d1107f937 ("bpf: support raw tracepoints in modules")
Acked-by: Martin KaFai Lau <kafai@...com>
Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
---
 kernel/trace/bpf_trace.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d255bc9b2bfa..23a390aac524 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2060,10 +2060,12 @@ struct bpf_raw_event_map *bpf_get_raw_tracepoint(const char *name)
 
 void bpf_put_raw_tracepoint(struct bpf_raw_event_map *btp)
 {
-	struct module *mod = __module_address((unsigned long)btp);
+	struct module *mod;
 
-	if (mod)
-		module_put(mod);
+	preempt_disable();
+	mod = __module_address((unsigned long)btp);
+	module_put(mod);
+	preempt_enable();
 }
 
 static __always_inline
-- 
2.24.1