[PATCH 5.10 295/717] bpf: Fix bpf_put_raw_tracepoint()s use of __module_address()

Greg Kroah-Hartman
2020-12-28T15:01:23Z

From: Andrii Nakryiko <andrii@kernel.org>

[ Upstream commit 12cc126df82c96c89706aa207ad27c56f219047c ]

__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")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-2-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.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 a125ea5e04cd7..0dde84b9d29fe 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2041,10 +2041,12 @@ 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
--
2.27.0