From: Alan Maguire <alan.maguire@oracle.com>
To: ast@kernel.org, daniel@iogearbox.net, yhs@fb.com
Cc: kafai@fb.com, songliubraving@fb.com, andriin@fb.com,
john.fastabend@gmail.com, kpsingh@chromium.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org, Alan Maguire <alan.maguire@oracle.com>
Subject: [RFC PATCH bpf-next 2/6] bpf: btf->resolved_[ids,sizes] should not be used for vmlinux BTF
Date: Fri, 17 Apr 2020 11:42:36 +0100 [thread overview]
Message-ID: <1587120160-3030-3-git-send-email-alan.maguire@oracle.com> (raw)
In-Reply-To: <1587120160-3030-1-git-send-email-alan.maguire@oracle.com>
When testing support for print data structures using patches
later in this series, I hit NULL pointer dereference bugs when
printing "struct sk_buff". The problem seems to revolve around
that structure's use of a zero-length array in the middle of
the data structure - headers_start[0].
We see in btf_type_id_size() we consult btf->resolved_ids and
btf->resolved_sizes; both of which are not used in kernel
vmlinux BTF so should not be used when handling vmlinux
BTF data.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
---
kernel/bpf/btf.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 50080ad..a474839 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -1170,7 +1170,7 @@ const struct btf_type *btf_type_id_size(const struct btf *btf,
if (btf_type_has_size(size_type)) {
size = size_type->size;
- } else if (btf_type_is_array(size_type)) {
+ } else if (btf_type_is_array(size_type) && btf->resolved_sizes) {
size = btf->resolved_sizes[size_type_id];
} else if (btf_type_is_ptr(size_type)) {
size = sizeof(void *);
@@ -1179,6 +1179,9 @@ const struct btf_type *btf_type_id_size(const struct btf *btf,
!btf_type_is_var(size_type)))
return NULL;
+ if (!btf->resolved_ids)
+ return NULL;
+
size_type_id = btf->resolved_ids[size_type_id];
size_type = btf_type_by_id(btf, size_type_id);
if (btf_type_nosize_or_null(size_type))
--
1.8.3.1
next prev parent reply other threads:[~2020-04-17 10:43 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-17 10:42 [RFC PATCH bpf-next 0/6] bpf, printk: add BTF-based type printing Alan Maguire
2020-04-17 10:42 ` [RFC PATCH bpf-next 1/6] bpf: provide function to get vmlinux BTF information Alan Maguire
2020-04-17 10:42 ` Alan Maguire [this message]
2020-04-17 10:42 ` [RFC PATCH bpf-next 3/6] bpf: move to generic BTF show support, apply it to seq files/strings Alan Maguire
2020-04-17 10:42 ` [RFC PATCH bpf-next 4/6] checkpatch: add new BTF pointer format specifier Alan Maguire
2020-04-17 10:42 ` [RFC PATCH bpf-next 5/6] printk: add type-printing %pT<type> format specifier which uses BTF Alan Maguire
2020-04-29 12:09 ` Rasmus Villemoes
2020-04-17 10:42 ` [RFC PATCH bpf-next 6/6] printk: extend test_printf to test %pT BTF-based format specifier Alan Maguire
2020-04-17 16:47 ` [RFC PATCH bpf-next 0/6] bpf, printk: add BTF-based type printing Arnaldo Carvalho de Melo
2020-04-17 17:06 ` Alan Maguire
2020-04-18 16:05 ` Alexei Starovoitov
2020-04-18 20:31 ` Arnaldo Melo
2020-04-20 15:29 ` Alan Maguire
2020-04-20 16:32 ` Joe Perches
2020-04-29 12:15 ` Rasmus Villemoes
2020-04-30 10:03 ` Alan Maguire
2020-05-02 0:25 ` Joe Perches
2020-04-20 20:54 ` Arnaldo Carvalho de Melo
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