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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, "Daniel T. Lee" <danieltimlee@gmail.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 190/276] selftests/bpf: ksym_search wont check symbols exists
Date:   Wed, 29 May 2019 20:05:48 -0700
Message-Id: <20190530030537.066337512@linuxfoundation.org>
In-Reply-To: <20190530030523.133519668@linuxfoundation.org>
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[ Upstream commit 0979ff7992fb6f4eb837995b12f4071dcafebd2d ]

Currently, ksym_search located at trace_helpers won't check symbols are
existing or not.

In ksym_search, when symbol is not found, it will return &syms[0](_stext).
But when the kernel symbols are not loaded, it will return NULL, which is
not a desired action.

This commit will add verification logic whether symbols are loaded prior
to the symbol search.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 tools/testing/selftests/bpf/trace_helpers.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index cabe2a3a3b300..cf156b3536798 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -51,6 +51,10 @@ struct ksym *ksym_search(long key)
 	int start = 0, end = sym_cnt;
 	int result;
 
+	/* kallsyms not loaded. return NULL */
+	if (sym_cnt <= 0)
+		return NULL;
+
 	while (start < end) {
 		size_t mid = start + (end - start) / 2;
 
-- 
2.20.1