On 2/21/24 10:25, Martin KaFai Lau wrote:
On 2/20/24 11:52 PM, thinker.li@xxxxxxxxx wrote:
From: Kui-Feng Lee <thinker.li@xxxxxxxxx>
Recently, cfi_stubs were introduced. However, existing struct_ops types
that are not in the upstream may not be aware of this, resulting in
kernel
crashes. By rejecting struct_ops types that do not provide cfi_stubs
during
registration, these crashes can be avoided.
Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
---
kernel/bpf/bpf_struct_ops.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 0d7be97a2411..c1c502caae08 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -302,6 +302,11 @@ int bpf_struct_ops_desc_init(struct
bpf_struct_ops_desc *st_ops_desc,
}
sprintf(value_name, "%s%s", VALUE_PREFIX, st_ops->name);
+ if (!st_ops->cfi_stubs) {
+ pr_warn("struct %s has no cfi_stubs\n", st_ops->name);
+ return -EINVAL;
+ }
+
type_id = btf_find_by_name_kind(btf, st_ops->name,
BTF_KIND_STRUCT);
if (type_id < 0) {
@@ -339,6 +344,7 @@ int bpf_struct_ops_desc_init(struct
bpf_struct_ops_desc *st_ops_desc,
for_each_member(i, t, member) {
const struct btf_type *func_proto;
+ u32 moff;
mname = btf_name_by_offset(btf, member->name_off);
if (!*mname) {
@@ -361,6 +367,17 @@ int bpf_struct_ops_desc_init(struct
bpf_struct_ops_desc *st_ops_desc,
if (!func_proto)
continue;
+ moff = __btf_member_bit_offset(t, member) / 8;
+ err = st_ops->check_member ?
+ st_ops->check_member(t, member, NULL) : 0;
I don't think it is necessary to make check_member more complicated by
taking
NULL prog. The struct_ops implementer then needs to handle this extra NULL
prog case.
Have you thought about Alexei's earlier suggestion in v3 to reuse the NULL
member in cfi_stubs to flag unsupported member and remove the
unsupported_ops[]
from bpf_tcp_ca.c?
If the verifier can consistently reject loading unsupported bpf prog, it
will
not reach the bpf_struct_ops_map_update_elem and then hits the NULL member
in cfi_stubs during map_update_elem.
Ok! I misunderstood previously. I will go this way.
