From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87241C07E9C for ; Thu, 8 Jul 2021 03:00:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 66E5D61CD8 for ; Thu, 8 Jul 2021 03:00:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230388AbhGHDDZ (ORCPT ); Wed, 7 Jul 2021 23:03:25 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:10429 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230201AbhGHDDY (ORCPT ); Wed, 7 Jul 2021 23:03:24 -0400 Received: from dggeme751-chm.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4GL1DS0scPzZqyG; Thu, 8 Jul 2021 10:57:28 +0800 (CST) Received: from [10.67.110.55] (10.67.110.55) by dggeme751-chm.china.huawei.com (10.3.19.97) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Thu, 8 Jul 2021 11:00:39 +0800 From: He Fengqing Subject: Re: [bpf-next 3/3] bpf: Fix a use after free in bpf_check() To: Song Liu CC: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , "David S . Miller" , Jakub Kicinski , Networking , bpf , open list References: <20210707043811.5349-1-hefengqing@huawei.com> <20210707043811.5349-4-hefengqing@huawei.com> Message-ID: <1c5b393d-6848-3d10-30cf-7063a331f76c@huawei.com> Date: Thu, 8 Jul 2021 11:00:39 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.110.55] X-ClientProxiedBy: dggeme714-chm.china.huawei.com (10.1.199.110) To dggeme751-chm.china.huawei.com (10.3.19.97) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/7/7 15:25, Song Liu 写道: > On Tue, Jul 6, 2021 at 8:53 PM He Fengqing wrote: >> >> In bpf_patch_insn_data, env->prog was input parameter of >> bpf_patch_insn_single function. bpf_patch_insn_single call >> bpf_prog_realloc to realloc ebpf prog. When we need to malloc new prog, >> bpf_prog_realloc will free the old prog, in this scenery is the >> env->prog. >> Then bpf_patch_insn_data function call adjust_insn_aux_data function, if >> adjust_insn_aux_data function return error, bpf_patch_insn_data will >> return NULL. >> In bpf_check->convert_ctx_accesses->bpf_patch_insn_data call chain, if >> bpf_patch_insn_data return NULL, env->prog has been freed in >> bpf_prog_realloc, then bpf_check will use the freed env->prog. > > Besides "what is the bug", please also describe "how to fix it". For example, > add "Fix it by adding a free_old argument to bpf_prog_realloc(), and ...". > Also, for the subject of 0/3, it is better to say "fix potential > memory leak and ...". Thanks for your suggestion. > >> >> Signed-off-by: He Fengqing >> --- >> include/linux/filter.h | 2 +- >> kernel/bpf/core.c | 9 ++++--- >> kernel/bpf/verifier.c | 53 ++++++++++++++++++++++++++++++++---------- >> net/core/filter.c | 2 +- >> 4 files changed, 49 insertions(+), 17 deletions(-) >> >> diff --git a/include/linux/filter.h b/include/linux/filter.h >> index f39e008a377d..ec11a5ae92c2 100644 >> --- a/include/linux/filter.h >> +++ b/include/linux/filter.h >> @@ -881,7 +881,7 @@ void bpf_prog_jit_attempt_done(struct bpf_prog *prog); >> struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags); >> struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flags); >> struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size, >> - gfp_t gfp_extra_flags); >> + gfp_t gfp_extra_flags, bool free_old); >> void __bpf_prog_free(struct bpf_prog *fp); >> >> static inline void bpf_prog_clone_free(struct bpf_prog *fp) >> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c >> index 49b0311f48c1..e5616bb1665b 100644 >> --- a/kernel/bpf/core.c >> +++ b/kernel/bpf/core.c >> @@ -218,7 +218,7 @@ void bpf_prog_fill_jited_linfo(struct bpf_prog *prog, >> } >> >> struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size, >> - gfp_t gfp_extra_flags) >> + gfp_t gfp_extra_flags, bool free_old) >> { >> gfp_t gfp_flags = GFP_KERNEL_ACCOUNT | __GFP_ZERO | gfp_extra_flags; >> struct bpf_prog *fp; >> @@ -238,7 +238,8 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size, >> /* We keep fp->aux from fp_old around in the new >> * reallocated structure. >> */ >> - bpf_prog_clone_free(fp_old); >> + if (free_old) >> + bpf_prog_clone_free(fp_old); >> } >> >> return fp; >> @@ -456,7 +457,7 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off, >> * last page could have large enough tailroom. >> */ >> prog_adj = bpf_prog_realloc(prog, bpf_prog_size(insn_adj_cnt), >> - GFP_USER); >> + GFP_USER, false); >> if (!prog_adj) >> return ERR_PTR(-ENOMEM); >> >> @@ -1150,6 +1151,8 @@ struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *prog) >> return tmp; >> } >> >> + if (tmp != clone) >> + bpf_prog_clone_free(clone); >> clone = tmp; >> insn_delta = rewritten - 1; >> >> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >> index 41109f49b724..e75b933f69e4 100644 >> --- a/kernel/bpf/verifier.c >> +++ b/kernel/bpf/verifier.c >> @@ -11855,7 +11855,10 @@ static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env, >> new_prog = bpf_patch_insn_data(env, adj_idx, patch, patch_len); >> if (!new_prog) >> return -ENOMEM; >> - env->prog = new_prog; >> + if (new_prog != env->prog) { >> + bpf_prog_clone_free(env->prog); >> + env->prog = new_prog; >> + } > > Can we move this check into bpf_patch_insn_data()? Ok, I will change this in next version. > >> insns = new_prog->insnsi; >> aux = env->insn_aux_data; >> delta += patch_len - 1; > [...] > >> diff --git a/net/core/filter.c b/net/core/filter.c >> index d70187ce851b..8a8d1a3ba5c2 100644 >> --- a/net/core/filter.c >> +++ b/net/core/filter.c >> @@ -1268,7 +1268,7 @@ static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp) >> >> /* Expand fp for appending the new filter representation. */ >> old_fp = fp; >> - fp = bpf_prog_realloc(old_fp, bpf_prog_size(new_len), 0); >> + fp = bpf_prog_realloc(old_fp, bpf_prog_size(new_len), 0, true); > > Can we add some logic here and not add free_old to bpf_prog_realloc()? Ok, maybe we can free old_fp here, never in bpf_prog_realloc. > > Thanks, > Song > . >