From patchwork Thu Jul 11 11:38:21 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xu Kuohai X-Patchwork-Id: 13730556 X-Patchwork-Delegate: paul@paul-moore.com Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4892F15F318; Thu, 11 Jul 2024 11:33:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720697597; cv=none; b=fAHarFmmwOnf3xW2gfSUk1ovMPW1WDOVpbeXf0a5pmnSl98wUR4Aa3A5WlaIm2v2Ws/VzWqPAjTTB5ztgzmhmeNkrcSKLSCxp175mKYomTd4POfJhk8yoswhfKkkeHOXW3lI2SQB0GlYyo/Lzo/Vq2T8twJU2QQkQ7UpUsEgS2M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720697597; c=relaxed/simple; bh=U/aVWd6GcCcklvM0eKm4aTu1GkOwloBt3ViFsr52kvc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=p+NqO5Ol6APBE7sqfORSd5tWgKySjzfLxEFiRdEIjbG3LJF0RDfjHpEh3ZH8LI8J2y/YMIaZDasLRO3V3tNgRwU6cKQ8GzPBujjffZp7XuoeciWkn62qNrEE6og/1CvVzOSpz8aBC/yWCNMJtweqskdF8o00Mi/3NYAKFPf/KCw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.235]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4WKXf70MWFz4f3kKV; Thu, 11 Jul 2024 19:33:03 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id AFA8E1A058E; Thu, 11 Jul 2024 19:33:10 +0800 (CST) Received: from k01.huawei.com (unknown [10.67.174.197]) by APP4 (Coremail) with SMTP id gCh0CgDXKvT0wo9mzI8hBw--.25380S2; Thu, 11 Jul 2024 19:33:10 +0800 (CST) From: Xu Kuohai To: bpf@vger.kernel.org, netdev@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-integrity@vger.kernel.org, apparmor@lists.ubuntu.com, selinux@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Matt Bobrowski , Brendan Jackman , Paul Moore , James Morris , "Serge E . Hallyn" , Khadija Kamran , Casey Schaufler , Ondrej Mosnacek , Kees Cook , John Johansen , Lukas Bulwahn , Roberto Sassu , Shung-Hsi Yu , Edward Cree , Alexander Viro , Christian Brauner , Trond Myklebust , Anna Schumaker , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Stephen Smalley Subject: [PATCH bpf-next v4 13/20] bpf, lsm: Add check for BPF LSM return value Date: Thu, 11 Jul 2024 19:38:21 +0800 Message-Id: <20240711113828.3818398-1-xukuohai@huaweicloud.com> X-Mailer: git-send-email 2.30.2 Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: gCh0CgDXKvT0wo9mzI8hBw--.25380S2 X-Coremail-Antispam: 1UD129KBjvJXoW3Wr1UAr1rGrykuFW8Ar4xJFb_yoWfArWxpF sxGryDAr4vvrW3uFnrtan7ZF1rJry0g3yIkF9rGryFyFWav3s5XF1qgryjvr1fCrWDCw1x Gr4jgrW5u347ZaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkIb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Gr0_Xr1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Cr0_Gr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I 0E14v26rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40E x7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x 0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1l42xK82IY c2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s 026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26rWY6r4UJwCIc40Y0x0EwIxGrwCI 42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42 IY6xAIw20EY4v20xvaj40_Wr1j6rW3Jr1lIxAIcVC2z280aVAFwI0_Gr0_Cr1lIxAIcVC2 z280aVCY1x0267AKxVWxJr0_GcJvcSsGvfC2KfnxnUUI43ZEXa7IU1c4S7UUUUU== X-CM-SenderInfo: 50xn30hkdlqx5xdzvxpfor3voofrz/ From: Xu Kuohai A bpf prog returning a positive number attached to file_alloc_security hook makes kernel panic. This happens because file system can not filter out the positive number returned by the LSM prog using IS_ERR, and misinterprets this positive number as a file pointer. Given that hook file_alloc_security never returned positive number before the introduction of BPF LSM, and other BPF LSM hooks may encounter similar issues, this patch adds LSM return value check in verifier, to ensure no unexpected value is returned. Fixes: 520b7aa00d8c ("bpf: lsm: Initialize the BPF LSM hooks") Reported-by: Xin Liu Signed-off-by: Xu Kuohai Acked-by: Eduard Zingerman --- include/linux/bpf.h | 1 + include/linux/bpf_lsm.h | 9 +++++++ kernel/bpf/bpf_lsm.c | 30 ++++++++++++++++++++- kernel/bpf/btf.c | 5 +++- kernel/bpf/verifier.c | 60 ++++++++++++++++++++++++++++++++++------- 5 files changed, 94 insertions(+), 11 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 4f1d4a97b9d1..d255201035c4 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -927,6 +927,7 @@ struct bpf_insn_access_aux { }; }; struct bpf_verifier_log *log; /* for verbose logs */ + bool is_retval; /* is accessing function return value ? */ }; static inline void diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h index 73e1f6dbec4a..ca5f2176c940 100644 --- a/include/linux/bpf_lsm.h +++ b/include/linux/bpf_lsm.h @@ -9,6 +9,7 @@ #include #include +#include #include #ifdef CONFIG_BPF_LSM @@ -47,6 +48,8 @@ void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, bpf_func_t *bpf_func) bool bpf_lsm_has_retval_param(const struct bpf_prog *prog); +int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *range); #else /* !CONFIG_BPF_LSM */ static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id) @@ -84,6 +87,12 @@ static inline bool bpf_lsm_has_retval_param(const struct bpf_prog *prog) { return false; } + +static inline int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *range) +{ + return -EOPNOTSUPP; +} #endif /* CONFIG_BPF_LSM */ #endif /* _LINUX_BPF_LSM_H */ diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index a8f8358c77e3..9dd338099d4a 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -11,7 +11,6 @@ #include #include #include -#include #include #include #include @@ -420,3 +419,32 @@ bool bpf_lsm_has_retval_param(const struct bpf_prog *prog) return btf_id_set_contains(&retval_param_lsm_hooks, prog->aux->attach_btf_id); } + +/* hooks return 0 or 1 */ +BTF_SET_START(bool_lsm_hooks) +BTF_ID(func, bpf_lsm_xfrm_state_pol_flow_match) +BTF_ID(func, bpf_lsm_audit_rule_known) +BTF_ID(func, bpf_lsm_inode_xattr_skipcap) +BTF_SET_END(bool_lsm_hooks) + +int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *retval_range) +{ + /* no return value range for void hooks */ + if (!prog->aux->attach_func_proto->type) + return -EINVAL; + + if (btf_id_set_contains(&bool_lsm_hooks, prog->aux->attach_btf_id)) { + retval_range->minval = 0; + retval_range->maxval = 1; + } else { + /* All other LSM hooks, except task_prctl, return 0 on success + * and negative error code on failure. + * To keep things simple, we only allow bpf progs to return 0 + * or negative errno for task_prctl. + */ + retval_range->minval = -MAX_ERRNO; + retval_range->maxval = 0; + } + return 0; +} diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index df299d600b10..ce892565367d 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6416,8 +6416,11 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, if (arg == nr_args) { switch (prog->expected_attach_type) { - case BPF_LSM_CGROUP: case BPF_LSM_MAC: + /* mark we are accessing the return value */ + info->is_retval = true; + fallthrough; + case BPF_LSM_CGROUP: case BPF_TRACE_FEXIT: /* When LSM programs are attached to void LSM hooks * they use FEXIT trampolines and when attached to diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a0bbef2d14e4..6f5d8ca995d6 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2334,6 +2334,25 @@ static void mark_reg_unknown(struct bpf_verifier_env *env, __mark_reg_unknown(env, regs + regno); } +static int __mark_reg_s32_range(struct bpf_verifier_env *env, + struct bpf_reg_state *regs, + u32 regno, + s32 s32_min, + s32 s32_max) +{ + struct bpf_reg_state *reg = regs + regno; + + reg->s32_min_value = max_t(s32, reg->s32_min_value, s32_min); + reg->s32_max_value = min_t(s32, reg->s32_max_value, s32_max); + + reg->smin_value = max_t(s64, reg->smin_value, s32_min); + reg->smax_value = min_t(s64, reg->smax_value, s32_max); + + reg_bounds_sync(reg); + + return reg_bounds_sanity_check(env, reg, "s32_range"); +} + static void __mark_reg_not_init(const struct bpf_verifier_env *env, struct bpf_reg_state *reg) { @@ -5587,11 +5606,12 @@ static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, /* check access to 'struct bpf_context' fields. Supports fixed offsets only */ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size, enum bpf_access_type t, enum bpf_reg_type *reg_type, - struct btf **btf, u32 *btf_id) + struct btf **btf, u32 *btf_id, bool *is_retval) { struct bpf_insn_access_aux info = { .reg_type = *reg_type, .log = &env->log, + .is_retval = false, }; if (env->ops->is_valid_access && @@ -5604,6 +5624,7 @@ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, * type of narrower access. */ *reg_type = info.reg_type; + *is_retval = info.is_retval; if (base_type(*reg_type) == PTR_TO_BTF_ID) { *btf = info.btf; @@ -6803,6 +6824,17 @@ static int check_stack_access_within_bounds( return grow_stack_state(env, state, -min_off /* size */); } +static bool get_func_retval_range(struct bpf_prog *prog, + struct bpf_retval_range *range) +{ + if (prog->type == BPF_PROG_TYPE_LSM && + prog->expected_attach_type == BPF_LSM_MAC && + !bpf_lsm_get_retval_range(prog, range)) { + return true; + } + return false; +} + /* check whether memory at (regno + off) is accessible for t = (read | write) * if t==write, value_regno is a register which value is stored into memory * if t==read, value_regno is a register which will receive the value from memory @@ -6907,6 +6939,8 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn if (!err && value_regno >= 0 && (t == BPF_READ || rdonly_mem)) mark_reg_unknown(env, regs, value_regno); } else if (reg->type == PTR_TO_CTX) { + bool is_retval = false; + struct bpf_retval_range range; enum bpf_reg_type reg_type = SCALAR_VALUE; struct btf *btf = NULL; u32 btf_id = 0; @@ -6922,7 +6956,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn return err; err = check_ctx_access(env, insn_idx, off, size, t, ®_type, &btf, - &btf_id); + &btf_id, &is_retval); if (err) verbose_linfo(env, insn_idx, "; "); if (!err && t == BPF_READ && value_regno >= 0) { @@ -6931,7 +6965,14 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn * case, we know the offset is zero. */ if (reg_type == SCALAR_VALUE) { - mark_reg_unknown(env, regs, value_regno); + if (is_retval && get_func_retval_range(env->prog, &range)) { + err = __mark_reg_s32_range(env, regs, value_regno, + range.minval, range.maxval); + if (err) + return err; + } else { + mark_reg_unknown(env, regs, value_regno); + } } else { mark_reg_known_zero(env, regs, value_regno); @@ -15782,12 +15823,13 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char case BPF_PROG_TYPE_LSM: if (env->prog->expected_attach_type != BPF_LSM_CGROUP) { - /* Regular BPF_PROG_TYPE_LSM programs can return - * any value. - */ - return 0; - } - if (!env->prog->aux->attach_func_proto->type) { + /* no range found, any return value is allowed */ + if (!get_func_retval_range(env->prog, &range)) + return 0; + /* no restricted range, any return value is allowed */ + if (range.minval == S32_MIN && range.maxval == S32_MAX) + return 0; + } else if (!env->prog->aux->attach_func_proto->type) { /* Make sure programs that attach to void * hooks don't try to modify return value. */