Linux-Modules Archive on lore.kernel.org
 help / color / Atom feed
From: Kees Cook <keescook@chromium.org>
To: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: linux-security-module <linux-security-module@vger.kernel.org>,
	"Luis R. Rodriguez" <mcgrof@suse.com>,
	Kexec Mailing List <kexec@lists.infradead.org>,
	linux-modules@vger.kernel.org,
	David Howells <dhowells@redhat.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH v3 07/22] vfs: define a generic function to read a file from the kernel
Date: Thu, 4 Feb 2016 09:41:00 -0800
Message-ID: <CAGXu5jKZxGseSjZvGHnRX7LBtWXYGA6r0u9dLAod1wQ8GC1+zQ@mail.gmail.com> (raw)
In-Reply-To: <1454526390-19792-8-git-send-email-zohar@linux.vnet.ibm.com>

On Wed, Feb 3, 2016 at 11:06 AM, Mimi Zohar <zohar@linux.vnet.ibm.com> wrote:
> For a while it was looked down upon to directly read files from Linux.
> These days there exists a few mechanisms in the kernel that do just
> this though to load a file into a local buffer.  There are minor but
> important checks differences on each.  This patch set is the first
> attempt at resolving some of these differences.
>
> This patch introduces a common function for reading files from the kernel
> with the corresponding security post-read hook and function.
>
> Changelog v3:
> - additional bounds checking - Luis
> v2:
> - To simplify patch review, re-ordered patches
>
> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> Reviewed-by: Luis R. Rodriguez <mcgrof@suse.com>

Acked-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>  fs/exec.c                 | 53 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/fs.h        |  1 +
>  include/linux/lsm_hooks.h |  9 ++++++++
>  include/linux/security.h  |  7 +++++++
>  security/security.c       |  7 +++++++
>  5 files changed, 77 insertions(+)
>
> diff --git a/fs/exec.c b/fs/exec.c
> index b06623a..742de7a 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -56,6 +56,7 @@
>  #include <linux/pipe_fs_i.h>
>  #include <linux/oom.h>
>  #include <linux/compat.h>
> +#include <linux/vmalloc.h>
>
>  #include <asm/uaccess.h>
>  #include <asm/mmu_context.h>
> @@ -831,6 +832,58 @@ int kernel_read(struct file *file, loff_t offset,
>
>  EXPORT_SYMBOL(kernel_read);
>
> +int kernel_read_file(struct file *file, void **buf, loff_t *size,
> +                    loff_t max_size)
> +{
> +       loff_t i_size, pos;
> +       ssize_t bytes = 0;
> +       int ret;
> +
> +       if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
> +               return -EINVAL;
> +
> +       i_size = i_size_read(file_inode(file));
> +       if (max_size > 0 && i_size > max_size)
> +               return -EFBIG;
> +       if (i_size <= 0)
> +               return -EINVAL;
> +
> +       *buf = vmalloc(i_size);
> +       if (!*buf)
> +               return -ENOMEM;
> +
> +       pos = 0;
> +       while (pos < i_size) {
> +               bytes = kernel_read(file, pos, (char *)(*buf) + pos,
> +                                   i_size - pos);
> +               if (bytes < 0) {
> +                       ret = bytes;
> +                       goto out;
> +               }
> +
> +               if (bytes == 0)
> +                       break;
> +               pos += bytes;
> +       }
> +
> +       if (pos != i_size) {
> +               ret = -EIO;
> +               goto out;
> +       }
> +
> +       ret = security_kernel_post_read_file(file, *buf, i_size);
> +       if (!ret)
> +               *size = pos;
> +
> +out:
> +       if (ret < 0) {
> +               vfree(*buf);
> +               *buf = NULL;
> +       }
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(kernel_read_file);
> +
>  ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
>  {
>         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 3aa5142..93ca379 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2527,6 +2527,7 @@ static inline void i_readcount_inc(struct inode *inode)
>  extern int do_pipe_flags(int *, int);
>
>  extern int kernel_read(struct file *, loff_t, char *, unsigned long);
> +extern int kernel_read_file(struct file *, void **, loff_t *, loff_t);
>  extern ssize_t kernel_write(struct file *, const char *, size_t, loff_t);
>  extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
>  extern struct file * open_exec(const char *);
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 71969de..f82631c 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -561,6 +561,13 @@
>   *     the kernel module to load. If the module is being loaded from a blob,
>   *     this argument will be NULL.
>   *     Return 0 if permission is granted.
> + * @kernel_post_read_file:
> + *     Read a file specified by userspace.
> + *     @file contains the file structure pointing to the file being read
> + *     by the kernel.
> + *     @buf pointer to buffer containing the file contents.
> + *     @size length of the file contents.
> + *     Return 0 if permission is granted.
>   * @task_fix_setuid:
>   *     Update the module's state after setting one or more of the user
>   *     identity attributes of the current process.  The @flags parameter
> @@ -1457,6 +1464,7 @@ union security_list_options {
>         int (*kernel_fw_from_file)(struct file *file, char *buf, size_t size);
>         int (*kernel_module_request)(char *kmod_name);
>         int (*kernel_module_from_file)(struct file *file);
> +       int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size);
>         int (*task_fix_setuid)(struct cred *new, const struct cred *old,
>                                 int flags);
>         int (*task_setpgid)(struct task_struct *p, pid_t pgid);
> @@ -1716,6 +1724,7 @@ struct security_hook_heads {
>         struct list_head kernel_act_as;
>         struct list_head kernel_create_files_as;
>         struct list_head kernel_fw_from_file;
> +       struct list_head kernel_post_read_file;
>         struct list_head kernel_module_request;
>         struct list_head kernel_module_from_file;
>         struct list_head task_fix_setuid;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 4824a4c..f30f564 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -301,6 +301,7 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode);
>  int security_kernel_fw_from_file(struct file *file, char *buf, size_t size);
>  int security_kernel_module_request(char *kmod_name);
>  int security_kernel_module_from_file(struct file *file);
> +int security_kernel_post_read_file(struct file *file, char *buf, loff_t size);
>  int security_task_fix_setuid(struct cred *new, const struct cred *old,
>                              int flags);
>  int security_task_setpgid(struct task_struct *p, pid_t pgid);
> @@ -866,6 +867,12 @@ static inline int security_kernel_module_from_file(struct file *file)
>         return 0;
>  }
>
> +static inline int security_kernel_post_read_file(struct file *file,
> +                                                char *buf, loff_t size)
> +{
> +       return 0;
> +}
> +
>  static inline int security_task_fix_setuid(struct cred *new,
>                                            const struct cred *old,
>                                            int flags)
> diff --git a/security/security.c b/security/security.c
> index e8ffd92..ae50730 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -910,6 +910,11 @@ int security_kernel_module_from_file(struct file *file)
>         return ima_module_check(file);
>  }
>
> +int security_kernel_post_read_file(struct file *file, char *buf, loff_t size)
> +{
> +       return call_int_hook(kernel_post_read_file, 0, file, buf, size);
> +}
> +
>  int security_task_fix_setuid(struct cred *new, const struct cred *old,
>                              int flags)
>  {
> @@ -1697,6 +1702,8 @@ struct security_hook_heads security_hook_heads = {
>                 LIST_HEAD_INIT(security_hook_heads.kernel_module_request),
>         .kernel_module_from_file =
>                 LIST_HEAD_INIT(security_hook_heads.kernel_module_from_file),
> +       .kernel_post_read_file =
> +               LIST_HEAD_INIT(security_hook_heads.kernel_post_read_file),
>         .task_fix_setuid =
>                 LIST_HEAD_INIT(security_hook_heads.task_fix_setuid),
>         .task_setpgid = LIST_HEAD_INIT(security_hook_heads.task_setpgid),
> --
> 2.1.0
>



-- 
Kees Cook
Chrome OS & Brillo Security

  reply index

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-03 19:06 [PATCH v3 00/22] vfs: support for a common kernel file loader Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 01/22] ima: separate 'security.ima' reading functionality from collect Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 02/22] ima: refactor ima_policy_show() to display "ima_hooks" rules Mimi Zohar
2016-02-07 19:45   ` Petko Manolov
2016-02-10 19:33   ` Dmitry Kasatkin
2016-02-03 19:06 ` [PATCH v3 03/22] ima: use "ima_hooks" enum as function argument Mimi Zohar
2016-02-07 19:46   ` Petko Manolov
2016-02-10 19:35   ` Dmitry Kasatkin
2016-02-03 19:06 ` [PATCH v3 04/22] firmware: simplify dev_*() print messages for generic helpers Mimi Zohar
2016-02-04 17:26   ` Kees Cook
2016-02-03 19:06 ` [PATCH v3 05/22] firmware: move completing fw into a helper Mimi Zohar
2016-02-04 17:27   ` Kees Cook
2016-02-03 19:06 ` [PATCH v3 06/22] firmware: fold successful fw read early Mimi Zohar
2016-02-04 17:36   ` Kees Cook
2016-02-04 20:26     ` Luis R. Rodriguez
2016-02-03 19:06 ` [PATCH v3 07/22] vfs: define a generic function to read a file from the kernel Mimi Zohar
2016-02-04 17:41   ` Kees Cook [this message]
2016-02-03 19:06 ` [PATCH v3 08/22] vfs: define kernel_read_file_id enumeration Mimi Zohar
2016-02-04 17:41   ` Kees Cook
2016-02-04 19:45   ` Luis R. Rodriguez
2016-02-03 19:06 ` [PATCH v3 09/22] ima: provide buffer hash calculation function Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 10/22] ima: calculate the hash of a buffer using aynchronous hash(ahash) Mimi Zohar
2016-02-10 19:58   ` Dmitry Kasatkin
2016-02-03 19:06 ` [PATCH v3 11/22] ima: define a new hook to measure and appraise a file already in memory Mimi Zohar
2016-02-10 20:27   ` Dmitry Kasatkin
2016-02-03 19:06 ` [PATCH v3 12/22] vfs: define kernel_read_file_from_path Mimi Zohar
2016-02-04 17:46   ` Kees Cook
2016-02-04 19:47   ` Luis R. Rodriguez
2016-02-03 19:06 ` [PATCH v3 13/22] firmware: replace call to fw_read_file_contents() with kernel version Mimi Zohar
2016-02-04 17:56   ` Kees Cook
2016-02-04 19:51   ` Luis R. Rodriguez
2016-02-03 19:06 ` [PATCH v3 14/22] security: define kernel_read_file hook Mimi Zohar
2016-02-04 17:57   ` Kees Cook
2016-02-04 19:54   ` Luis R. Rodriguez
2016-02-11 16:54   ` Casey Schaufler
2016-02-11 19:35     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 15/22] vfs: define kernel_copy_file_from_fd() Mimi Zohar
2016-02-04 17:58   ` Kees Cook
2016-02-04 19:55   ` Luis R. Rodriguez
2016-02-03 19:06 ` [PATCH v3 16/22] module: replace copy_module_from_fd with kernel version Mimi Zohar
2016-02-04 18:04   ` Kees Cook
2016-02-04 19:56   ` Luis R. Rodriguez
2016-02-05  0:19     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 17/22] ima: remove firmware and module specific cached status info Mimi Zohar
2016-02-07 19:56   ` Petko Manolov
2016-02-10 20:18   ` Dmitry Kasatkin
2016-02-10 23:14     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 18/22] kexec: replace call to copy_file_from_fd() with kernel version Mimi Zohar
2016-02-04 18:05   ` Kees Cook
2016-02-04 19:57   ` Luis R. Rodriguez
2016-02-12 12:50   ` Dave Young
2016-02-03 19:06 ` [PATCH v3 19/22] ima: support for kexec image and initramfs Mimi Zohar
2016-02-07 20:10   ` Petko Manolov
2016-02-08 23:34     ` Mimi Zohar
2016-02-10 21:09   ` Dmitry Kasatkin
2016-02-10 23:21     ` Mimi Zohar
     [not found]       ` <CACE9dm8OJ1cgbKszUG-pCiEMVarUFLLWi_jewVV-JEMGAJsA-g@mail.gmail.com>
2016-02-11  2:08         ` Mimi Zohar
2016-02-11  8:47           ` Dmitry Kasatkin
2016-02-11 12:16             ` Mimi Zohar
2016-02-12 12:53   ` Dave Young
2016-02-12 13:09     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 20/22] ima: load policy using path Mimi Zohar
2016-02-07 19:59   ` Petko Manolov
2016-02-08  9:58     ` Dmitry Kasatkin
2016-02-08 10:35       ` Petko Manolov
2016-02-08 10:45         ` Dmitry Kasatkin
2016-02-08 21:12           ` Mimi Zohar
2016-02-09  7:47             ` Petko Manolov
2016-02-03 19:06 ` [PATCH v3 21/22] ima: measure and appraise the IMA policy itself Mimi Zohar
2016-02-07 20:01   ` Petko Manolov
2016-02-10 20:22   ` Dmitry Kasatkin
2016-02-10 23:15     ` Mimi Zohar
2016-02-03 19:06 ` [PATCH v3 22/22] ima: require signed IMA policy Mimi Zohar
2016-02-07 20:02   ` Petko Manolov
2016-02-10 20:24   ` Dmitry Kasatkin
2016-02-04 18:15 ` [PATCH v3 00/22] vfs: support for a common kernel file loader Kees Cook
2016-02-04 23:54   ` Mimi Zohar

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAGXu5jKZxGseSjZvGHnRX7LBtWXYGA6r0u9dLAod1wQ8GC1+zQ@mail.gmail.com \
    --to=keescook@chromium.org \
    --cc=dhowells@redhat.com \
    --cc=dmitry.kasatkin@gmail.com \
    --cc=dmitry.torokhov@gmail.com \
    --cc=dwmw2@infradead.org \
    --cc=ebiederm@xmission.com \
    --cc=kexec@lists.infradead.org \
    --cc=linux-modules@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=mcgrof@suse.com \
    --cc=rusty@rustcorp.com.au \
    --cc=zohar@linux.vnet.ibm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Modules Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-modules/0 linux-modules/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-modules linux-modules/ https://lore.kernel.org/linux-modules \
		linux-modules@vger.kernel.org linux-modules@archiver.kernel.org
	public-inbox-index linux-modules


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-modules


AGPL code for this site: git clone https://public-inbox.org/ public-inbox