On Thu, Apr 11, 2024 at 5:24 AM Xu Kuohai <[email protected]> wrote: > > From: Xu Kuohai <[email protected]> > > 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_retval_range is a 32-bit range, this patch fixes it by > changing the compare between r0 and return range from 64-bit > operation to 32-bit operation. > > Fixes: 8fa4ecd49b81 ("bpf: enforce exact retval range on subprog/callback > exit") > Signed-off-by: Xu Kuohai <[email protected]> > --- > kernel/bpf/verifier.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 05c7c5f2bec0..5393d576c76f 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -9879,7 +9879,7 @@ static bool in_rbtree_lock_required_cb(struct > bpf_verifier_env *env) > > static bool retval_range_within(struct bpf_retval_range range, const struct > bpf_reg_state *reg) > { > - return range.minval <= reg->smin_value && reg->smax_value <= > range.maxval; > + return range.minval <= reg->s32_min_value && reg->s32_max_value <= > range.maxval;
are all BPF programs treated as if they return int instead of long? If not, we probably should have a bool flag in bpf_retval_range whether comparison should be 32-bit or 64-bit? > } > > static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) > -- > 2.30.2 >
