From patchwork Tue Jul 28 16:34:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 11689513 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A434E138A for ; Tue, 28 Jul 2020 16:34:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8793220792 for ; Tue, 28 Jul 2020 16:34:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="lEJ+hCVH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731700AbgG1Qer (ORCPT ); Tue, 28 Jul 2020 12:34:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731687AbgG1Qeq (ORCPT ); Tue, 28 Jul 2020 12:34:46 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61EEBC061794; Tue, 28 Jul 2020 09:34:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=RSxXaY46qjfEfo21QTpQuE55JqNPBx/9VQ1LMRWiW5M=; b=lEJ+hCVHys8yl21i8p4u0uuAAq lurWG95UoMC61IC0nXnS/E4PRS31Tuo6oOFJSYBX5ZXBc/WYjR6nsfiU9V/PSHnH3ZWwc0UKks1PY g9ayjXHHa7PettEcd2lwMNdLd9JNtdfkEMwTSDxpHT/SqATBdwfQbkM2mCaRS6qGkrLEPyluagz5G pN9JQcCdkqAnM0SP092CdWEIo60tUzB26rMTx7zjMxG4ZM/MZtfOz5vMGaf1yKwzfsVGBgci/o8B/ 0Pg+sLk5QoRx64H/PPLGnhx2E84kmkEq28f+MROahXPnJq4btasqSw4PjSMDaPRSRssoOKQXWVA1C S/1fBXJw==; Received: from [2001:4bb8:180:6102:fd04:50d8:4827:5508] (helo=localhost) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1k0SYr-00070X-N1; Tue, 28 Jul 2020 16:34:42 +0000 From: Christoph Hellwig To: Al Viro , Linus Torvalds Cc: Greg Kroah-Hartman , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org Subject: [PATCH 13/23] init: add an init_chroot helper Date: Tue, 28 Jul 2020 18:34:06 +0200 Message-Id: <20200728163416.556521-14-hch@lst.de> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200728163416.556521-1-hch@lst.de> References: <20200728163416.556521-1-hch@lst.de> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add a simple helper to chroot with a kernel space file name and switch the early init code over to it. Remove the now unused ksys_chroot. Signed-off-by: Christoph Hellwig --- drivers/base/devtmpfs.c | 2 +- fs/init.c | 24 ++++++++++++++++++++++++ fs/open.c | 7 +------ include/linux/init_syscalls.h | 1 + include/linux/syscalls.h | 2 -- init/do_mounts.c | 2 +- init/do_mounts_initrd.c | 4 ++-- 7 files changed, 30 insertions(+), 12 deletions(-) diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c index e48aaba3166b5d..eac184e6d65774 100644 --- a/drivers/base/devtmpfs.c +++ b/drivers/base/devtmpfs.c @@ -413,7 +413,7 @@ static int __init devtmpfs_setup(void *p) if (err) goto out; init_chdir("/.."); /* will traverse into overmounted root */ - ksys_chroot("."); + init_chroot("."); out: *(int *)p = err; complete(&setup_done); diff --git a/fs/init.c b/fs/init.c index 64d4e12eba9339..2c78f24814dde4 100644 --- a/fs/init.c +++ b/fs/init.c @@ -9,6 +9,7 @@ #include #include #include +#include #include "internal.h" int __init init_mount(const char *dev_name, const char *dir_name, @@ -54,6 +55,29 @@ int __init init_chdir(const char *filename) return error; } +int __init init_chroot(const char *filename) +{ + struct path path; + int error; + + error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path); + if (error) + return error; + error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR); + if (error) + goto dput_and_out; + error = -EPERM; + if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT)) + goto dput_and_out; + error = security_path_chroot(&path); + if (error) + goto dput_and_out; + set_fs_root(current->fs, &path); +dput_and_out: + path_put(&path); + return error; +} + int __init init_unlink(const char *pathname) { return do_unlinkat(AT_FDCWD, getname_kernel(pathname)); diff --git a/fs/open.c b/fs/open.c index 723e0ac898935e..f62f4752bb436d 100644 --- a/fs/open.c +++ b/fs/open.c @@ -530,7 +530,7 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd) return error; } -int ksys_chroot(const char __user *filename) +SYSCALL_DEFINE1(chroot, const char __user *, filename) { struct path path; int error; @@ -563,11 +563,6 @@ int ksys_chroot(const char __user *filename) return error; } -SYSCALL_DEFINE1(chroot, const char __user *, filename) -{ - return ksys_chroot(filename); -} - static int chmod_common(const struct path *path, umode_t mode) { struct inode *inode = path->dentry->d_inode; diff --git a/include/linux/init_syscalls.h b/include/linux/init_syscalls.h index 1e845910ae56e9..e07099a14b91db 100644 --- a/include/linux/init_syscalls.h +++ b/include/linux/init_syscalls.h @@ -4,5 +4,6 @@ int __init init_mount(const char *dev_name, const char *dir_name, const char *type_page, unsigned long flags, void *data_page); int __init init_umount(const char *name, int flags); int __init init_chdir(const char *filename); +int __init init_chroot(const char *filename); int __init init_unlink(const char *pathname); int __init init_rmdir(const char *pathname); diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 31fa67fb9894b3..e89d62e944dc0e 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -1235,8 +1235,6 @@ asmlinkage long sys_ni_syscall(void); * Instead, use one of the functions which work equivalently, such as * the ksys_xyzyyz() functions prototyped below. */ - -int ksys_chroot(const char __user *filename); ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count); int ksys_fchown(unsigned int fd, uid_t user, gid_t group); ssize_t ksys_read(unsigned int fd, char __user *buf, size_t count); diff --git a/init/do_mounts.c b/init/do_mounts.c index a7581c6e85f268..b5f9604d0c98a2 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -629,7 +629,7 @@ void __init prepare_namespace(void) out: devtmpfs_mount(); init_mount(".", "/", NULL, MS_MOVE, NULL); - ksys_chroot("."); + init_chroot("."); } static bool is_tmpfs; diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c index 04627fd22a921f..a6b447b191dbc8 100644 --- a/init/do_mounts_initrd.c +++ b/init/do_mounts_initrd.c @@ -63,7 +63,7 @@ static int __init init_linuxrc(struct subprocess_info *info, struct cred *new) /* move initrd over / and chdir/chroot in initrd root */ init_chdir("/root"); init_mount(".", "/", NULL, MS_MOVE, NULL); - ksys_chroot("."); + init_chroot("."); ksys_setsid(); return 0; } @@ -101,7 +101,7 @@ static void __init handle_initrd(void) /* move initrd to rootfs' /old */ init_mount("..", ".", NULL, MS_MOVE, NULL); /* switch root and cwd back to / of rootfs */ - ksys_chroot(".."); + init_chroot(".."); if (new_decode_dev(real_root_dev) == Root_RAM0) { init_chdir("/old");