From: Yonghong Song <yhs@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>
Subject: [PATCH bpf 1/2] bpf: fix a bug when getting subprog 0 jited image in check_attach_btf_id
Date: Wed, 4 Dec 2019 17:06:06 -0800 [thread overview]
Message-ID: <20191205010606.177774-1-yhs@fb.com> (raw)
In-Reply-To: <20191205010606.177712-1-yhs@fb.com>
For jited bpf program, if the subprogram count is 1, i.e.,
there is no callees in the program, prog->aux->func will be NULL
and prog->bpf_func points to image address of the program.
If there is more than one subprogram, prog->aux->func is populated,
and subprogram 0 can be accessed through either prog->bpf_func or
prog->aux->func[0]. Other subprograms should be accessed through
prog->aux->func[subprog_id].
This patch fixed a bug in check_attach_btf_id(), where
prog->aux->func[subprog_id] is used to access any subprogram which
caused a segfault like below:
[79162.619208] BUG: kernel NULL pointer dereference, address:
0000000000000000
......
[79162.634255] Call Trace:
[79162.634974] ? _cond_resched+0x15/0x30
[79162.635686] ? kmem_cache_alloc_trace+0x162/0x220
[79162.636398] ? selinux_bpf_prog_alloc+0x1f/0x60
[79162.637111] bpf_prog_load+0x3de/0x690
[79162.637809] __do_sys_bpf+0x105/0x1740
[79162.638488] do_syscall_64+0x5b/0x180
[79162.639147] entry_SYSCALL_64_after_hwframe+0x44/0xa9
......
Fixes: 5b92a28aae4d ("bpf: Support attaching tracing BPF program to other BPF programs")
Reported-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
kernel/bpf/verifier.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a0482e1c4a77..034ef81f935b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9636,7 +9636,10 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
ret = -EINVAL;
goto out;
}
- addr = (long) tgt_prog->aux->func[subprog]->bpf_func;
+ if (subprog == 0)
+ addr = (long) tgt_prog->bpf_func;
+ else
+ addr = (long) tgt_prog->aux->func[subprog]->bpf_func;
} else {
addr = kallsyms_lookup_name(tname);
if (!addr) {
--
2.17.1
next prev parent reply other threads:[~2019-12-05 1:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-05 1:06 [PATCH bpf 0/2] fix a verifier bug in check_attach_btf_id() Yonghong Song
2019-12-05 1:06 ` Yonghong Song [this message]
2019-12-05 5:33 ` [PATCH bpf 1/2] bpf: fix a bug when getting subprog 0 jited image in check_attach_btf_id Alexei Starovoitov
2019-12-05 1:06 ` [PATCH bpf 2/2] selftests/bpf: add a fexit/bpf2bpf test with target bpf prog no callees Yonghong Song
2019-12-05 5:37 ` Alexei Starovoitov
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