From: Alexei Starovoitov <ast@kernel.org>
To: <davem@davemloft.net>
Cc: <daniel@iogearbox.net>, <netdev@vger.kernel.org>,
<bpf@vger.kernel.org>, <kernel-team@fb.com>
Subject: [PATCH bpf] bpf: Fix modifier skipping logic
Date: Fri, 31 Jan 2020 16:03:14 -0800 [thread overview]
Message-ID: <20200201000314.261392-1-ast@kernel.org> (raw)
Fix the way modifiers are skipped while walking pointers. Otherwise second
level dereferences of 'const struct foo *' will be rejected by the verifier.
Fixes: 9e15db66136a ("bpf: Implement accurate raw_tp context access via BTF")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
kernel/bpf/btf.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index b7c1660fb594..a289f2915ba8 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3931,6 +3931,7 @@ int btf_struct_access(struct bpf_verifier_log *log,
if (btf_type_is_ptr(mtype)) {
const struct btf_type *stype;
+ u32 id;
if (msize != size || off != moff) {
bpf_log(log,
@@ -3939,12 +3940,9 @@ int btf_struct_access(struct bpf_verifier_log *log,
return -EACCES;
}
- stype = btf_type_by_id(btf_vmlinux, mtype->type);
- /* skip modifiers */
- while (btf_type_is_modifier(stype))
- stype = btf_type_by_id(btf_vmlinux, stype->type);
+ stype = btf_type_skip_modifiers(btf_vmlinux, mtype->type, &id);
if (btf_type_is_struct(stype)) {
- *next_btf_id = mtype->type;
+ *next_btf_id = id;
return PTR_TO_BTF_ID;
}
}
--
2.23.0
next reply other threads:[~2020-02-01 0:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-01 0:03 Alexei Starovoitov [this message]
2020-02-01 0:46 ` [PATCH bpf] bpf: Fix modifier skipping logic Yonghong Song
2020-02-03 23:10 ` Daniel Borkmann
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