netdev - [PATCH bpf-next] bpf: Fix bpf jit kallsym access

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Date:   Wed, 30 Oct 2019 16:30:19 -0700
From:   Alexei Starovoitov <ast@...nel.org>
To:     <davem@...emloft.net>
CC:     <daniel@...earbox.net>, <jolsa@...hat.com>,
        <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
        <kernel-team@...com>
Subject: [PATCH bpf-next] bpf: Fix bpf jit kallsym access

Jiri reported crash when JIT is on, but net.core.bpf_jit_kallsyms is off.
bpf_prog_kallsyms_find() was skipping addr->bpf_prog resolution
logic in oops and stack traces. That's incorrect.
It should only skip addr->name resolution for 'cat /proc/kallsyms'.
That's what bpf_jit_kallsyms and bpf_jit_harden protect.

Reported-by: Jiri Olsa <jolsa@...hat.com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Fixes: 3dec541b2e63 ("bpf: Add support for BTF pointers to x86 JIT")
---
 kernel/bpf/core.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 673f5d40a93e..8d3fbc86ca5e 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -668,9 +668,6 @@ static struct bpf_prog *bpf_prog_kallsyms_find(unsigned long addr)
 {
 	struct latch_tree_node *n;
 
-	if (!bpf_jit_kallsyms_enabled())
-		return NULL;
-
 	n = latch_tree_find((void *)addr, &bpf_tree, &bpf_tree_ops);
 	return n ?
 	       container_of(n, struct bpf_prog_aux, ksym_tnode)->prog :
-- 
2.17.1