From patchwork Tue Sep 6 17:02:55 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 12967967 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 B7E80C6FA89 for ; Tue, 6 Sep 2022 17:49:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229681AbiIFRt1 (ORCPT ); Tue, 6 Sep 2022 13:49:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229473AbiIFRt0 (ORCPT ); Tue, 6 Sep 2022 13:49:26 -0400 X-Greylist: delayed 1500 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Tue, 06 Sep 2022 10:49:17 PDT Received: from frasgout11.his.huawei.com (frasgout11.his.huawei.com [14.137.139.23]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95474895C5; Tue, 6 Sep 2022 10:49:16 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.18.147.229]) by frasgout11.his.huawei.com (SkyGuard) with ESMTP id 4MMWmd6CcNz9v7Hb; Wed, 7 Sep 2022 00:58:25 +0800 (CST) Received: from huaweicloud.com (unknown [10.204.63.22]) by APP1 (Coremail) with SMTP id LxC2BwA34JNSfRdjftYoAA--.8234S3; Tue, 06 Sep 2022 18:03:37 +0100 (CET) From: Roberto Sassu To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, mykolal@fb.com, shuah@kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, jakub@cloudflare.com Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, houtao1@huawei.com, Roberto Sassu , stable@vger.kernel.org Subject: [PATCH 1/7] bpf: Add missing fd modes check for map iterators Date: Tue, 6 Sep 2022 19:02:55 +0200 Message-Id: <20220906170301.256206-2-roberto.sassu@huaweicloud.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220906170301.256206-1-roberto.sassu@huaweicloud.com> References: <20220906170301.256206-1-roberto.sassu@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: LxC2BwA34JNSfRdjftYoAA--.8234S3 X-Coremail-Antispam: 1UD129KBjvJXoW3XrWkCF43Kr4xJFyDKryxAFb_yoWxWr1rpF 15tryxCay0qrW7urZ5Xw4DA345Aw4UXw13Ga9Yqa4F9rsagrnrXr18uF1aqFy5ZFW8KFya yrsFk3yrA3yxZrDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPqb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6r1S6rWUM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUGw A2048vs2IY020Ec7CjxVAFwI0_Xr0E3s1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxS w2x7M28EF7xvwVC0I7IYx2IY67AKxVWUCVW8JwA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxV W8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_Gr0_Cr1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6r4UJVWxJr1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2 WlYx0E2Ix0cI8IcVAFwI0_Jrv_JF1lYx0Ex4A2jsIE14v26r4j6F4UMcvjeVCFs4IE7xkE bVWUJVW8JwACjcxG0xvY0x0EwIxGrwACI402YVCY1x02628vn2kIc2xKxwCY1x0262kKe7 AKxVW8ZVWrXwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02 F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_GFv_Wr ylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI42IY6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI 0_Gr0_Cr1lIxAIcVC2z280aVCY1x0267AKxVW8Jr0_Cr1UYxBIdaVFxhVjvjDU0xZFpf9x 07jaeHgUUUUU= X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAgAHBF1jj36uhwAAsn X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Roberto Sassu Commit 6e71b04a82248 ("bpf: Add file mode configuration into bpf maps") added the BPF_F_RDONLY and BPF_F_WRONLY flags, to let user space specify whether it will just read or modify a map. Map access control is done in two steps. First, when user space wants to obtain a map fd, it provides to the kernel the eBPF-defined flags, which are converted into open flags and passed to the security_bpf_map() security hook for evaluation by LSMs. Second, if user space successfully obtained an fd, it passes that fd to the kernel when it requests a map operation (e.g. lookup or update). The kernel first checks if the fd has the modes required to perform the requested operation and, if yes, continues the execution and returns the result to user space. While the fd modes check was added for map_*_elem() functions, it is currently missing for map iterators, added more recently with commit a5cbe05a6673 ("bpf: Implement bpf iterator for map elements"). A map iterator executes a chosen eBPF program for each key/value pair of a map and allows that program to read and/or modify them. Whether a map iterator allows only read or also write depends on whether the MEM_RDONLY flag in the ctx_arg_info member of the bpf_iter_reg structure is set. Also, write needs to be supported at verifier level (for example, it is currently not supported for sock maps). Since map iterators obtain a map from a user space fd with bpf_map_get_with_uref(), add the new req_modes parameter to that function, so that map iterators can provide the required fd modes to access a map. If the user space fd doesn't include the required modes, bpf_map_get_with_uref() returns with an error, and the map iterator will not be created. If a map iterator marks both the key and value as read-only, it calls bpf_map_get_with_uref() with FMODE_CAN_READ as value for req_modes. If it also allows write access to either the key or the value, it calls that function with FMODE_CAN_READ | FMODE_CAN_WRITE as value for req_modes, regardless of whether or not the write is supported by the verifier (the write is intentionally allowed). bpf_fd_probe_obj() does not require any fd mode, as the fd is only used for the purpose of finding the eBPF object type, for pinning the object to the bpffs filesystem. Finally, it is worth to mention that the fd modes check was not added for the cgroup iterator, although it registers an attach_target method like the other iterators. The reason is that the fd is not the only way for user space to reference a cgroup object (also by ID and by path). For the protection to be effective, all reference methods need to be evaluated consistently. This work is deferred to a separate patch. Cc: stable@vger.kernel.org # 5.10.x Fixes: a5cbe05a6673 ("bpf: Implement bpf iterator for map elements") Signed-off-by: Roberto Sassu --- include/linux/bpf.h | 2 +- kernel/bpf/inode.c | 2 +- kernel/bpf/map_iter.c | 3 ++- kernel/bpf/syscall.c | 8 +++++++- net/core/bpf_sk_storage.c | 3 ++- net/core/sock_map.c | 3 ++- 6 files changed, 15 insertions(+), 6 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 9c1674973e03..6cd2ca910553 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1628,7 +1628,7 @@ bool bpf_map_equal_kptr_off_tab(const struct bpf_map *map_a, const struct bpf_ma void bpf_map_free_kptrs(struct bpf_map *map, void *map_value); struct bpf_map *bpf_map_get(u32 ufd); -struct bpf_map *bpf_map_get_with_uref(u32 ufd); +struct bpf_map *bpf_map_get_with_uref(u32 ufd, fmode_t req_modes); struct bpf_map *__bpf_map_get(struct fd f); void bpf_map_inc(struct bpf_map *map); void bpf_map_inc_with_uref(struct bpf_map *map); diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index 4f841e16779e..862e1caa8b0f 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -71,7 +71,7 @@ static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type) { void *raw; - raw = bpf_map_get_with_uref(ufd); + raw = bpf_map_get_with_uref(ufd, 0); if (!IS_ERR(raw)) { *type = BPF_TYPE_MAP; return raw; diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c index b0fa190b0979..1143f8960135 100644 --- a/kernel/bpf/map_iter.c +++ b/kernel/bpf/map_iter.c @@ -110,7 +110,8 @@ static int bpf_iter_attach_map(struct bpf_prog *prog, if (!linfo->map.map_fd) return -EBADF; - map = bpf_map_get_with_uref(linfo->map.map_fd); + map = bpf_map_get_with_uref(linfo->map.map_fd, + FMODE_CAN_READ | FMODE_CAN_WRITE); if (IS_ERR(map)) return PTR_ERR(map); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 4e9d4622aef7..4a2063d8e99c 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1232,7 +1232,7 @@ struct bpf_map *bpf_map_get(u32 ufd) } EXPORT_SYMBOL(bpf_map_get); -struct bpf_map *bpf_map_get_with_uref(u32 ufd) +struct bpf_map *bpf_map_get_with_uref(u32 ufd, fmode_t req_modes) { struct fd f = fdget(ufd); struct bpf_map *map; @@ -1241,7 +1241,13 @@ struct bpf_map *bpf_map_get_with_uref(u32 ufd) if (IS_ERR(map)) return map; + if ((map_get_sys_perms(map, f) & req_modes) != req_modes) { + map = ERR_PTR(-EPERM); + goto out; + } + bpf_map_inc_with_uref(map); +out: fdput(f); return map; diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c index 1b7f385643b4..bf9c6afed8ac 100644 --- a/net/core/bpf_sk_storage.c +++ b/net/core/bpf_sk_storage.c @@ -897,7 +897,8 @@ static int bpf_iter_attach_map(struct bpf_prog *prog, if (!linfo->map.map_fd) return -EBADF; - map = bpf_map_get_with_uref(linfo->map.map_fd); + map = bpf_map_get_with_uref(linfo->map.map_fd, + FMODE_CAN_READ | FMODE_CAN_WRITE); if (IS_ERR(map)) return PTR_ERR(map); diff --git a/net/core/sock_map.c b/net/core/sock_map.c index a660baedd9e7..7f7375dc39b2 100644 --- a/net/core/sock_map.c +++ b/net/core/sock_map.c @@ -1636,7 +1636,8 @@ static int sock_map_iter_attach_target(struct bpf_prog *prog, if (!linfo->map.map_fd) return -EBADF; - map = bpf_map_get_with_uref(linfo->map.map_fd); + map = bpf_map_get_with_uref(linfo->map.map_fd, + FMODE_CAN_READ | FMODE_CAN_WRITE); if (IS_ERR(map)) return PTR_ERR(map);