diff options
| -rw-r--r-- | kernel/bpf/verifier.c | 88 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/progs/dynptr_fail.c | 6 |
2 files changed, 91 insertions, 3 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 76afdbea425a..5c7f29ca94ec 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -769,6 +769,8 @@ static void mark_dynptr_cb_reg(struct bpf_reg_state *reg, __mark_dynptr_reg(reg, type, true); } +static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env *env, + struct bpf_func_state *state, int spi); static int mark_stack_slots_dynptr(struct bpf_verifier_env *env, struct bpf_reg_state *reg, enum bpf_arg_type arg_type, int insn_idx) @@ -863,6 +865,55 @@ static int unmark_stack_slots_dynptr(struct bpf_verifier_env *env, struct bpf_re return 0; } +static void __mark_reg_unknown(const struct bpf_verifier_env *env, + struct bpf_reg_state *reg); + +static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env *env, + struct bpf_func_state *state, int spi) +{ + int i; + + /* We always ensure that STACK_DYNPTR is never set partially, + * hence just checking for slot_type[0] is enough. This is + * different for STACK_SPILL, where it may be only set for + * 1 byte, so code has to use is_spilled_reg. + */ + if (state->stack[spi].slot_type[0] != STACK_DYNPTR) + return 0; + + /* Reposition spi to first slot */ + if (!state->stack[spi].spilled_ptr.dynptr.first_slot) + spi = spi + 1; + + if (dynptr_type_refcounted(state->stack[spi].spilled_ptr.dynptr.type)) { + verbose(env, "cannot overwrite referenced dynptr\n"); + return -EINVAL; + } + + mark_stack_slot_scratched(env, spi); + mark_stack_slot_scratched(env, spi - 1); + + /* Writing partially to one dynptr stack slot destroys both. */ + for (i = 0; i < BPF_REG_SIZE; i++) { + state->stack[spi].slot_type[i] = STACK_INVALID; + state->stack[spi - 1].slot_type[i] = STACK_INVALID; + } + + /* TODO: Invalidate any slices associated with this dynptr */ + + /* Do not release reference state, we are destroying dynptr on stack, + * not using some helper to release it. Just reset register. + */ + __mark_reg_not_init(env, &state->stack[spi].spilled_ptr); + __mark_reg_not_init(env, &state->stack[spi - 1].spilled_ptr); + + /* Same reason as unmark_stack_slots_dynptr above */ + state->stack[spi].spilled_ptr.live |= REG_LIVE_WRITTEN; + state->stack[spi - 1].spilled_ptr.live |= REG_LIVE_WRITTEN; + + return 0; +} + static bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env *env, struct bpf_reg_state *reg) { struct bpf_func_state *state = func(env, reg); @@ -3391,6 +3442,10 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env, env->insn_aux_data[insn_idx].sanitize_stack_spill = true; } + err = destroy_if_dynptr_stack_slot(env, state, spi); + if (err) + return err; + mark_stack_slot_scratched(env, spi); if (reg && !(off % BPF_REG_SIZE) && register_is_bounded(reg) && !register_is_null(reg) && env->bpf_capable) { @@ -3504,6 +3559,14 @@ static int check_stack_write_var_off(struct bpf_verifier_env *env, if (err) return err; + for (i = min_off; i < max_off; i++) { + int spi; + + spi = __get_spi(i); + err = destroy_if_dynptr_stack_slot(env, state, spi); + if (err) + return err; + } /* Variable offset writes destroy any spilled pointers in range. */ for (i = min_off; i < max_off; i++) { @@ -5531,6 +5594,31 @@ static int check_stack_range_initialized( } if (meta && meta->raw_mode) { + /* Ensure we won't be overwriting dynptrs when simulating byte + * by byte access in check_helper_call using meta.access_size. + * This would be a problem if we have a helper in the future + * which takes: + * + * helper(uninit_mem, len, dynptr) + * + * Now, uninint_mem may overlap with dynptr pointer. Hence, it + * may end up writing to dynptr itself when touching memory from + * arg 1. This can be relaxed on a case by case basis for known + * safe cases, but reject due to the possibilitiy of aliasing by + * default. + */ + for (i = min_off; i < max_off + access_size; i++) { + int stack_off = -i - 1; + + spi = __get_spi(i); + /* raw_mode may write past allocated_stack */ + if (state->allocated_stack <= stack_off) + continue; + if (state->stack[spi].slot_type[stack_off % BPF_REG_SIZE] == STACK_DYNPTR) { + verbose(env, "potential write to dynptr at off=%d disallowed\n", i); + return -EACCES; + } + } meta->access_size = access_size; meta->regno = regno; return 0; diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c index 02d57b95cf6e..9dc3f23a8270 100644 --- a/tools/testing/selftests/bpf/progs/dynptr_fail.c +++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c @@ -420,7 +420,7 @@ int invalid_write1(void *ctx) * offset */ SEC("?raw_tp") -__failure __msg("Expected an initialized dynptr as arg #3") +__failure __msg("cannot overwrite referenced dynptr") int invalid_write2(void *ctx) { struct bpf_dynptr ptr; @@ -444,7 +444,7 @@ int invalid_write2(void *ctx) * non-const offset */ SEC("?raw_tp") -__failure __msg("Expected an initialized dynptr as arg #1") +__failure __msg("cannot overwrite referenced dynptr") int invalid_write3(void *ctx) { struct bpf_dynptr ptr; @@ -476,7 +476,7 @@ static int invalid_write4_callback(__u32 index, void *data) * be invalidated as a dynptr */ SEC("?raw_tp") -__failure __msg("arg 1 is an unacquired reference") +__failure __msg("cannot overwrite referenced dynptr") int invalid_write4(void *ctx) { struct bpf_dynptr ptr; |