Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933577AbcJRKGz (ORCPT ); Tue, 18 Oct 2016 06:06:55 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:6856 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1759518AbcJRKGg (ORCPT ); Tue, 18 Oct 2016 06:06:36 -0400 X-IronPort-AV: E=Sophos;i="5.22,518,1449504000"; d="scan'208";a="12059140" From: Cao Shufeng To: CC: , , , , , , , , Subject: [PATCH v3.1 2/3] Limit dump_pipe program's permission to init for container Date: Tue, 18 Oct 2016 18:06:36 +0800 Message-ID: <1476785197-5048-3-git-send-email-caosf.fnst@cn.fujitsu.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1476785197-5048-1-git-send-email-caosf.fnst@cn.fujitsu.com> References: <1476785197-5048-1-git-send-email-caosf.fnst@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.167.226.94] X-yoursite-MailScanner-ID: 1F70D41B5F44.A11E5 X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: caosf.fnst@cn.fujitsu.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6085 Lines: 212 From: Zhao Lei Currently when we set core_pattern to a pipe, the pipe program is forked by kthread running with root's permission, and write dumpfile into host's filesystem. Same thing happened for container, the dumper and dumpfile are also in host(not in container). It have following program: 1: Not consistent with file_type core_pattern When we set core_pattern to a file, the container will write dump into container's filesystem instead of host. 2: Not safe for privileged container In a privileged container, user can destroy host system by following command: # # In a container # echo "|/bin/dd of=/boot/vmlinuz" >/proc/sys/kernel/core_pattern # make_dump This patch switch dumper program's environment to init task, so, for container, dumper program have same environment with init task in container, which make dumper program put in container's filesystem, and write coredump into container's filesystem. The dumper's permission is also limited into subset of container's init process. Suggested-by: Eric W. Biederman Suggested-by: KOSAKI Motohiro Signed-off-by: Zhao Lei Co-Authored-By: Cao ShuFeng --- fs/coredump.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++- include/linux/binfmts.h | 1 + 2 files changed, 102 insertions(+), 2 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index ceb0ee8..8ea8bc1 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -501,6 +501,23 @@ static void wait_for_dump_helpers(struct file *file) pipe_unlock(pipe); } +static int umh_ns_setup(struct subprocess_info *info) +{ + struct coredump_params *cp = (struct coredump_params *)info->data; + struct task_struct *base_task = cp->base_task; + + if (base_task) { + /* Set namespaces to base_task */ + get_nsproxy(base_task->nsproxy); + switch_task_namespaces(current, base_task->nsproxy); + + /* Return -EAGAIN to notice caller to refork */ + return -EAGAIN; + } + + return 0; +} + /* * umh_pipe_setup * helper function to customize the process used @@ -516,6 +533,8 @@ static int umh_pipe_setup(struct subprocess_info *info, struct cred *new) { struct file *files[2]; struct coredump_params *cp = (struct coredump_params *)info->data; + struct task_struct *base_task; + int err = create_pipe_files(files, 0); if (err) return err; @@ -524,10 +543,76 @@ static int umh_pipe_setup(struct subprocess_info *info, struct cred *new) err = replace_fd(0, files[0], 0); fput(files[0]); + if (err) + return err; + /* and disallow core files too */ current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1}; - return err; + base_task = cp->base_task; + if (base_task) { + const struct cred *base_cred; + + /* Set fs_root to base_task */ + spin_lock(&base_task->fs->lock); + set_fs_root(current->fs, &base_task->fs->root); + set_fs_pwd(current->fs, &base_task->fs->pwd); + spin_unlock(&base_task->fs->lock); + + /* Set cgroup to base_task */ + current->flags &= ~PF_NO_SETAFFINITY; + err = cgroup_attach_task_all(base_task, current); + if (err < 0) + return err; + + /* Set cred to base_task */ + base_cred = get_task_cred(base_task); + + new->uid = base_cred->uid; + new->gid = base_cred->gid; + new->suid = base_cred->suid; + new->sgid = base_cred->sgid; + new->euid = base_cred->euid; + new->egid = base_cred->egid; + new->fsuid = base_cred->fsuid; + new->fsgid = base_cred->fsgid; + + new->securebits = base_cred->securebits; + + new->cap_inheritable = base_cred->cap_inheritable; + new->cap_permitted = base_cred->cap_permitted; + new->cap_effective = base_cred->cap_effective; + new->cap_bset = base_cred->cap_bset; + new->cap_ambient = base_cred->cap_ambient; + + security_cred_free(new); +#ifdef CONFIG_SECURITY + new->security = NULL; +#endif + err = security_prepare_creds(new, base_cred, GFP_KERNEL); + if (err < 0) { + put_cred(base_cred); + return err; + } + + free_uid(new->user); + new->user = base_cred->user; + get_uid(new->user); + + put_user_ns(new->user_ns); + new->user_ns = base_cred->user_ns; + get_user_ns(new->user_ns); + + put_group_info(new->group_info); + new->group_info = base_cred->group_info; + get_group_info(new->group_info); + + put_cred(base_cred); + + validate_creds(new); + } + + return 0; } void do_coredump(const siginfo_t *siginfo) @@ -590,6 +675,7 @@ void do_coredump(const siginfo_t *siginfo) if (ispipe) { int dump_count; + struct task_struct *vinit_task; char **helper_argv; struct subprocess_info *sub_info; @@ -631,6 +717,14 @@ void do_coredump(const siginfo_t *siginfo) goto fail_dropcount; } + rcu_read_lock(); + vinit_task = find_task_by_vpid(1); + rcu_read_unlock(); + if (!vinit_task) { + printk(KERN_WARNING "failed getting init task info, skipping core dump\n"); + goto fail_dropcount; + } + helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL); if (!helper_argv) { printk(KERN_WARNING "%s failed to allocate memory\n", @@ -638,15 +732,20 @@ void do_coredump(const siginfo_t *siginfo) goto fail_dropcount; } + get_task_struct(vinit_task); + + cprm.base_task = vinit_task; + retval = -ENOMEM; sub_info = call_usermodehelper_setup(helper_argv[0], helper_argv, NULL, GFP_KERNEL, - NULL, umh_pipe_setup, + umh_ns_setup, umh_pipe_setup, NULL, &cprm); if (sub_info) retval = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC); + put_task_struct(vinit_task); argv_free(helper_argv); if (retval) { printk(KERN_INFO "Core dump to |%s pipe failed\n", diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 1303b57..193d269 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -59,6 +59,7 @@ struct linux_binprm { /* Function parameter for binfmt->coredump */ struct coredump_params { + struct task_struct *base_task; const siginfo_t *siginfo; struct pt_regs *regs; struct file *file; -- 2.7.4