Now kfunc call uses s32 to represent the offset between the address of kfunc and __bpf_call_base, but it doesn't check whether or not s32 will be overflowed, so add an extra checking to reject these invalid kfunc calls. Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> --- v2: * instead of checking the overflow in selftests, just reject these kfunc calls directly in verifier v1: https://lore.kernel.org/bpf/20220206043107.18549-1-houtao1@xxxxxxxxxx --- kernel/bpf/verifier.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a39eedecc93a..fd836e64b701 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1832,6 +1832,13 @@ static struct btf *find_kfunc_desc_btf(struct bpf_verifier_env *env, return btf_vmlinux ?: ERR_PTR(-ENOENT); } +static inline bool is_kfunc_call_imm_overflowed(unsigned long addr) +{ + unsigned long offset = BPF_CALL_IMM(addr); + + return (unsigned long)(s32)offset != offset; +} + static int add_kfunc_call(struct bpf_verifier_env *env, u32 func_id, s16 offset) { const struct btf_type *func, *func_proto; @@ -1925,6 +1932,12 @@ static int add_kfunc_call(struct bpf_verifier_env *env, u32 func_id, s16 offset) return -EINVAL; } + if (is_kfunc_call_imm_overflowed(addr)) { + verbose(env, "address of kernel function %s is out of range\n", + func_name); + return -EINVAL; + } + desc = &tab->descs[tab->nr_descs++]; desc->func_id = func_id; desc->imm = BPF_CALL_IMM(addr); -- 2.29.2
