From patchwork Tue Aug 9 21:40:54 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joanne Koong X-Patchwork-Id: 12939953 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 791D4C19F2D for ; Tue, 9 Aug 2022 21:42:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229460AbiHIVlw (ORCPT ); Tue, 9 Aug 2022 17:41:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229818AbiHIVla (ORCPT ); Tue, 9 Aug 2022 17:41:30 -0400 Received: from 66-220-155-178.mail-mxout.facebook.com (66-220-155-178.mail-mxout.facebook.com [66.220.155.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 897AC6556A for ; Tue, 9 Aug 2022 14:41:27 -0700 (PDT) Received: by devbig010.atn6.facebook.com (Postfix, from userid 115148) id D15D61031CEF1; Tue, 9 Aug 2022 14:41:13 -0700 (PDT) From: Joanne Koong To: bpf@vger.kernel.org Cc: kafai@fb.com, void@manifault.com, andrii@kernel.org, daniel@iogearbox.net, ast@kernel.org, Joanne Koong Subject: [PATCH bpf-next v4 1/2] bpf: Fix ref_obj_id for dynptr data slices in verifier Date: Tue, 9 Aug 2022 14:40:54 -0700 Message-Id: <20220809214055.4050604-1-joannelkoong@gmail.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net When a data slice is obtained from a dynptr (through the bpf_dynptr_data API), the ref obj id of the dynptr must be found and then associated with the data slice. The ref obj id of the dynptr must be found *before* the caller saved regs are reset. Without this fix, the ref obj id tracking is not correct for dynptrs that are at an offset from the frame pointer. Please also note that the data slice's ref obj id must be assigned after the ret types are parsed, since RET_PTR_TO_ALLOC_MEM-type return regs get zero-marked. Fixes: 34d4ef5775f776ec4b0d53a02d588bf3195cada6 ("bpf: Add dynptr data slices"); Signed-off-by: Joanne Koong Acked-by: David Vernet --- kernel/bpf/verifier.c | 38 ++++++++++++++++++++------------------ 1 file changed, 20 insertions(+), 18 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 01e7f48b4d8c..28b02dc67a2a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -504,7 +504,7 @@ static bool is_ptr_cast_function(enum bpf_func_id func_id) func_id == BPF_FUNC_skc_to_tcp_request_sock; } -static bool is_dynptr_acquire_function(enum bpf_func_id func_id) +static bool is_dynptr_ref_function(enum bpf_func_id func_id) { return func_id == BPF_FUNC_dynptr_data; } @@ -518,7 +518,7 @@ static bool helper_multiple_ref_obj_use(enum bpf_func_id func_id, ref_obj_uses++; if (is_acquire_function(func_id, map)) ref_obj_uses++; - if (is_dynptr_acquire_function(func_id)) + if (is_dynptr_ref_function(func_id)) ref_obj_uses++; return ref_obj_uses > 1; @@ -7320,6 +7320,23 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn } } break; + case BPF_FUNC_dynptr_data: + for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) { + if (arg_type_is_dynptr(fn->arg_type[i])) { + if (meta.ref_obj_id) { + verbose(env, "verifier internal error: meta.ref_obj_id already set\n"); + return -EFAULT; + } + /* Find the id of the dynptr we're tracking the reference of */ + meta.ref_obj_id = stack_slot_get_id(env, ®s[BPF_REG_1 + i]); + break; + } + } + if (i == MAX_BPF_FUNC_REG_ARGS) { + verbose(env, "verifier internal error: no dynptr in bpf_dynptr_data()\n"); + return -EFAULT; + } + break; } if (err) @@ -7457,7 +7474,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn return -EFAULT; } - if (is_ptr_cast_function(func_id)) { + if (is_ptr_cast_function(func_id) || is_dynptr_ref_function(func_id)) { /* For release_reference() */ regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id; } else if (is_acquire_function(func_id, meta.map_ptr)) { @@ -7469,21 +7486,6 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn regs[BPF_REG_0].id = id; /* For release_reference() */ regs[BPF_REG_0].ref_obj_id = id; - } else if (is_dynptr_acquire_function(func_id)) { - int dynptr_id = 0, i; - - /* Find the id of the dynptr we're tracking the reference of */ - for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) { - if (arg_type_is_dynptr(fn->arg_type[i])) { - if (dynptr_id) { - verbose(env, "verifier internal error: multiple dynptr args in func\n"); - return -EFAULT; - } - dynptr_id = stack_slot_get_id(env, ®s[BPF_REG_1 + i]); - } - } - /* For release_reference() */ - regs[BPF_REG_0].ref_obj_id = dynptr_id; } do_refine_retval_range(regs, fn->ret_type, func_id, &meta); From patchwork Tue Aug 9 21:40:55 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joanne Koong X-Patchwork-Id: 12939954 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EFB5C25B08 for ; Tue, 9 Aug 2022 21:42:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229541AbiHIVly (ORCPT ); Tue, 9 Aug 2022 17:41:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229819AbiHIVla (ORCPT ); Tue, 9 Aug 2022 17:41:30 -0400 Received: from 66-220-155-178.mail-mxout.facebook.com (66-220-155-178.mail-mxout.facebook.com [66.220.155.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A2A26556F for ; Tue, 9 Aug 2022 14:41:27 -0700 (PDT) Received: by devbig010.atn6.facebook.com (Postfix, from userid 115148) id E0F321031CF01; Tue, 9 Aug 2022 14:41:15 -0700 (PDT) From: Joanne Koong To: bpf@vger.kernel.org Cc: kafai@fb.com, void@manifault.com, andrii@kernel.org, daniel@iogearbox.net, ast@kernel.org, Joanne Koong Subject: [PATCH bpf-next v4 2/2] selftests/bpf: add extra test for using dynptr data slice after release Date: Tue, 9 Aug 2022 14:40:55 -0700 Message-Id: <20220809214055.4050604-2-joannelkoong@gmail.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220809214055.4050604-1-joannelkoong@gmail.com> References: <20220809214055.4050604-1-joannelkoong@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Add an additional test, "data_slice_use_after_release2", for ensuring that data slices are correctly invalidated by the verifier after the dynptr whose ref obj id they track is released. In particular, this tests data slice invalidation for dynptrs located at a non-zero offset from the frame pointer. Signed-off-by: Joanne Koong Acked-by: Martin KaFai Lau --- .../testing/selftests/bpf/prog_tests/dynptr.c | 3 +- .../testing/selftests/bpf/progs/dynptr_fail.c | 38 ++++++++++++++++++- 2 files changed, 39 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c index 3c7aa82b98e2..bcf80b9f7c27 100644 --- a/tools/testing/selftests/bpf/prog_tests/dynptr.c +++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c @@ -22,7 +22,8 @@ static struct { {"add_dynptr_to_map2", "invalid indirect read from stack"}, {"data_slice_out_of_bounds_ringbuf", "value is outside of the allowed memory range"}, {"data_slice_out_of_bounds_map_value", "value is outside of the allowed memory range"}, - {"data_slice_use_after_release", "invalid mem access 'scalar'"}, + {"data_slice_use_after_release1", "invalid mem access 'scalar'"}, + {"data_slice_use_after_release2", "invalid mem access 'scalar'"}, {"data_slice_missing_null_check1", "invalid mem access 'mem_or_null'"}, {"data_slice_missing_null_check2", "invalid mem access 'mem_or_null'"}, {"invalid_helper1", "invalid indirect read from stack"}, diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c index b5e0a87f0a36..b0f08ff024fb 100644 --- a/tools/testing/selftests/bpf/progs/dynptr_fail.c +++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c @@ -248,7 +248,7 @@ int data_slice_out_of_bounds_map_value(void *ctx) /* A data slice can't be used after it has been released */ SEC("?raw_tp") -int data_slice_use_after_release(void *ctx) +int data_slice_use_after_release1(void *ctx) { struct bpf_dynptr ptr; struct sample *sample; @@ -272,6 +272,42 @@ int data_slice_use_after_release(void *ctx) return 0; } +/* A data slice can't be used after it has been released. + * + * This tests the case where the data slice tracks a dynptr (ptr2) + * that is at a non-zero offset from the frame pointer (ptr1 is at fp, + * ptr2 is at fp - 16). + */ +SEC("?raw_tp") +int data_slice_use_after_release2(void *ctx) +{ + struct bpf_dynptr ptr1, ptr2; + struct sample *sample; + + bpf_ringbuf_reserve_dynptr(&ringbuf, 64, 0, &ptr1); + bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(*sample), 0, &ptr2); + + sample = bpf_dynptr_data(&ptr2, 0, sizeof(*sample)); + if (!sample) + goto done; + + sample->pid = 23; + + bpf_ringbuf_submit_dynptr(&ptr2, 0); + + /* this should fail */ + sample->pid = 23; + + bpf_ringbuf_submit_dynptr(&ptr1, 0); + + return 0; + +done: + bpf_ringbuf_discard_dynptr(&ptr2, 0); + bpf_ringbuf_discard_dynptr(&ptr1, 0); + return 0; +} + /* A data slice must be first checked for NULL */ SEC("?raw_tp") int data_slice_missing_null_check1(void *ctx)