6.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Xu Kuohai xukuohai@huawei.com
[ Upstream commit 763aa759d3b2c4f95b11855e3d37b860860107e2 ]
After checking lsm hook return range in verifier, the test case "test_progs -t test_lsm" failed, and the failure log says:
libbpf: prog 'test_int_hook': BPF program load failed: Invalid argument libbpf: prog 'test_int_hook': -- BEGIN PROG LOAD LOG -- 0: R1=ctx() R10=fp0 ; int BPF_PROG(test_int_hook, struct vm_area_struct *vma, @ lsm.c:89 0: (79) r0 = *(u64 *)(r1 +24) ; R0_w=scalar(smin=smin32=-4095,smax=smax32=0) R1=ctx()
[...]
24: (b4) w0 = -1 ; R0_w=0xffffffff ; int BPF_PROG(test_int_hook, struct vm_area_struct *vma, @ lsm.c:89 25: (95) exit At program exit the register R0 has smin=4294967295 smax=4294967295 should have been in [-4095, 0]
It can be seen that instruction "w0 = -1" zero extended -1 to 64-bit register r0, setting both smin and smax values of r0 to 4294967295. This resulted in a false reject when r0 was checked with range [-4095, 0].
Given bpf lsm does not return 64-bit values, this patch fixes it by changing the compare between r0 and return range from 64-bit operation to 32-bit operation for bpf lsm.
Fixes: 8fa4ecd49b81 ("bpf: enforce exact retval range on subprog/callback exit") Signed-off-by: Xu Kuohai xukuohai@huawei.com Acked-by: Shung-Hsi Yu shung-hsi.yu@suse.com Link: https://lore.kernel.org/r/20240719110059.797546-5-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/verifier.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b95f7f5bd5a49..203ce12e687d2 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9952,9 +9952,13 @@ static bool in_rbtree_lock_required_cb(struct bpf_verifier_env *env) return is_rbtree_lock_required_kfunc(kfunc_btf_id); }
-static bool retval_range_within(struct bpf_retval_range range, const struct bpf_reg_state *reg) +static bool retval_range_within(struct bpf_retval_range range, const struct bpf_reg_state *reg, + bool return_32bit) { - return range.minval <= reg->smin_value && reg->smax_value <= range.maxval; + if (return_32bit) + return range.minval <= reg->s32_min_value && reg->s32_max_value <= range.maxval; + else + return range.minval <= reg->smin_value && reg->smax_value <= range.maxval; }
static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) @@ -9991,8 +9995,8 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) if (err) return err;
- /* enforce R0 return value range */ - if (!retval_range_within(callee->callback_ret_range, r0)) { + /* enforce R0 return value range, and bpf_callback_t returns 64bit */ + if (!retval_range_within(callee->callback_ret_range, r0, false)) { verbose_invalid_scalar(env, r0, callee->callback_ret_range, "At callback return", "R0"); return -EINVAL; @@ -15613,6 +15617,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char int err; struct bpf_func_state *frame = env->cur_state->frame[0]; const bool is_subprog = frame->subprogno; + bool return_32bit = false;
/* LSM and struct_ops func-ptr's return type could be "void" */ if (!is_subprog || frame->in_exception_callback_fn) { @@ -15724,6 +15729,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char /* no restricted range, any return value is allowed */ if (range.minval == S32_MIN && range.maxval == S32_MAX) return 0; + return_32bit = true; } else if (!env->prog->aux->attach_func_proto->type) { /* Make sure programs that attach to void * hooks don't try to modify return value. @@ -15754,7 +15760,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char if (err) return err;
- if (!retval_range_within(range, reg)) { + if (!retval_range_within(range, reg, return_32bit)) { verbose_invalid_scalar(env, reg, range, exit_ctx, reg_name); if (!is_subprog && prog->expected_attach_type == BPF_LSM_CGROUP &&