From: Alexei Starovoitov <ast@xxxxxxxxxx>
Teach the verifier to recognize PTR_TO_MEM | MEM_RDONLY as not NULL
otherwise if (!bpf_ksym_exists(known_kfunc)) doesn't go through
dead code elimination.
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
kernel/bpf/verifier.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8bc44f5dc5b6..5693e4a92752 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -486,8 +486,17 @@ static bool type_is_sk_pointer(enum bpf_reg_type type)
type == PTR_TO_XDP_SOCK;
}
+static bool type_may_be_null(u32 type)
+{
+ return type & PTR_MAYBE_NULL;
+}
+
static bool reg_type_not_null(enum bpf_reg_type type)
{
+ if (type_may_be_null(type))
+ return false;
+
+ type = base_type(type);
return type == PTR_TO_SOCKET ||
type == PTR_TO_TCP_SOCK ||
type == PTR_TO_MAP_VALUE ||
@@ -531,11 +540,6 @@ static bool type_is_rdonly_mem(u32 type)
return type & MEM_RDONLY;
}
-static bool type_may_be_null(u32 type)
-{
- return type & PTR_MAYBE_NULL;
-}
-
static bool is_acquire_function(enum bpf_func_id func_id,
const struct bpf_map *map)
{
--
2.34.1
