diff mbox series

[v5,bpf-next,01/14] bpf: fix bpf_put_raw_tracepoint()'s use of __module_address()

Message ID 20201203035204.1411380-2-andrii@kernel.org (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series Support BTF-powered BPF tracing programs for kernel modules | expand

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netdev/tree_selection success Clearly marked for bpf-next
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netdev/source_inline success Was 0 now: 0
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netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 33 this patch: 33
netdev/kdoc success Errors and warnings before: 0 this patch: 0
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netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 15 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 33 this patch: 33
netdev/header_inline success Link
netdev/stable success Stable not CCed

Commit Message

Andrii Nakryiko Dec. 3, 2020, 3:51 a.m. UTC
__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@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 kernel/trace/bpf_trace.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Comments

John Fastabend Dec. 3, 2020, 4:36 a.m. UTC | #1
Andrii Nakryiko wrote:
> __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@fb.com>
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> ---

Acked-by: John Fastabend <john.fastabend@gmail.com>
diff mbox series

Patch

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