perf bpf: Return value with unlocking in perf_env__find_btf() [Linux 5.1]

perf bpf: Return value with unlocking in perf_env__find_btf() [Linux 5.1]

This Linux kernel change "perf bpf: Return value with unlocking in perf_env__find_btf()" is included in the Linux 5.1 release. This change is authored by Bo YU <tsu.yubo [at] gmail.com> on Mon Apr 22 04:01:38 2019 -0400. The commit for this change in Linux stable tree is 2e71267 (patch).

perf bpf: Return value with unlocking in perf_env__find_btf()

In perf_env__find_btf(), we're returning without unlocking
"env->bpf_progs.lock". There may be cause lockdep issue.

Detected by CoversityScan, CID# 1444762:(program hangs(LOCK))

Signed-off-by: Bo YU <tsu.yubo@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org
Fixes: 2db7b1e0bd49d: (perf bpf: Return NULL when RB tree lookup fails in perf_env__find_btf())
Link: http://lkml.kernel.org/r/20190422080138.10088-1-tsu.yubo@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

There are 2 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 tools/perf/util/env.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
index 9494f9d..6a3eaf7 100644
--- a/tools/perf/util/env.c
+++ b/tools/perf/util/env.c
@@ -115,8 +115,8 @@ struct btf_node *perf_env__find_btf(struct perf_env *env, __u32 btf_id)
    }
    node = NULL;

-   up_read(&env->bpf_progs.lock);
 out:
+   up_read(&env->bpf_progs.lock);
    return node;
 }

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