Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1204562 > unrolled thread

[PATCH v2 2/7] userns: Simpilify MNT_NODEV handling.

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  [PATCH v2 2/7] userns: Simpilify MNT_NODEV handling. Seth Forshee <seth.forshee@canonical.com> - 2015-08-10 23:10 +0200
    Re: [PATCH v2 2/7] userns: Simpilify MNT_NODEV handling. Seth Forshee <seth.forshee@canonical.com> - 2015-08-17 18:40 +0200

#1204562 — [PATCH v2 2/7] userns: Simpilify MNT_NODEV handling.

From: "Eric W. Biederman" <ebiederm@xmission.com>

- Consolidate the testing if a device node may be opened in a new
  function may_open_dev.

- Move the check for allowing access to device nodes on filesystems
  not mounted in the initial user namespace from mount time to open
  time and include it in may_open_dev.

This set of changes removes the implicit adding of MNT_NODEV which
simplifies the logic in fs/namespace.c and removes a potentially
problematic user visible difference in how normal and unprivileged
mount namespaces work.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/block_dev.c     |  2 +-
 fs/namei.c         |  9 ++++++++-
 fs/namespace.c     | 18 ++++--------------
 include/linux/fs.h |  1 +
 4 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 198243717da5..f8ce371c437c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1729,7 +1729,7 @@ struct block_device *lookup_bdev(const char *pathname)
 	if (!S_ISBLK(inode->i_mode))
 		goto fail;
 	error = -EACCES;
-	if (path.mnt->mnt_flags & MNT_NODEV)
+	if (!may_open_dev(&path))
 		goto fail;
 	error = -ENOMEM;
 	bdev = bd_acquire(inode);
diff --git a/fs/namei.c b/fs/namei.c
index fbbcf0993312..59444c066f47 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2640,6 +2640,13 @@ int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 }
 EXPORT_SYMBOL(vfs_create);
 
+bool may_open_dev(const struct path *path)
+{
+	return !(path->mnt->mnt_flags & MNT_NODEV) &&
+		((path->mnt->mnt_sb->s_user_ns == &init_user_ns) ||
+		 (path->mnt->mnt_sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT));
+}
+
 static int may_open(struct path *path, int acc_mode, int flag)
 {
 	struct dentry *dentry = path->dentry;
@@ -2662,7 +2669,7 @@ static int may_open(struct path *path, int acc_mode, int flag)
 		break;
 	case S_IFBLK:
 	case S_IFCHR:
-		if (path->mnt->mnt_flags & MNT_NODEV)
+		if (!may_open_dev(path))
 			return -EACCES;
 		/*FALLTHRU*/
 	case S_IFIFO:
diff --git a/fs/namespace.c b/fs/namespace.c
index d023a353dc63..e48fa1c23378 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2177,13 +2177,7 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
 	}
 	if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
 	    !(mnt_flags & MNT_NODEV)) {
-		/* Was the nodev implicitly added in mount? */
-		if ((mnt->mnt_ns->user_ns != &init_user_ns) &&
-		    !(sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT)) {
-			mnt_flags |= MNT_NODEV;
-		} else {
-			return -EPERM;
-		}
+		return -EPERM;
 	}
 	if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) &&
 	    !(mnt_flags & MNT_NOSUID)) {
@@ -2396,13 +2390,6 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
 			put_filesystem(type);
 			return -EPERM;
 		}
-		/* Only in special cases allow devices from mounts
-		 * created outside the initial user namespace.
-		 */
-		if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
-			flags |= MS_NODEV;
-			mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
-		}
 		if (type->fs_flags & FS_USERNS_VISIBLE) {
 			if (!fs_fully_visible(type, &mnt_flags))
 				return -EPERM;
@@ -3238,6 +3225,9 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
 		mnt_flags = mnt->mnt.mnt_flags;
 		if (mnt->mnt.mnt_sb->s_iflags & SB_I_NOEXEC)
 			mnt_flags &= ~(MNT_LOCK_NOSUID | MNT_LOCK_NOEXEC);
+		if (current_user_ns() != &init_user_ns &&
+		    !(mnt->mnt.mnt_sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT))
+			mnt_flags &= ~(MNT_LOCK_NODEV);
 
 		/* Verify the mount flags are equal to or more permissive
 		 * than the proposed new mount.
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6242e9629fe6..4a60e76f86ac 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1527,6 +1527,7 @@ extern void dentry_unhash(struct dentry *dentry);
  */
 extern void inode_init_owner(struct inode *inode, const struct inode *dir,
 			umode_t mode);
+extern bool may_open_dev(const struct path *path);
 /*
  * VFS FS_IOC_FIEMAP helper definitions.
  */
-- 
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [next] | [standalone]

#1208710

On Mon, Aug 10, 2015 at 04:05:13PM -0500, Seth Forshee wrote:
> From: "Eric W. Biederman" <ebiederm@xmission.com>
> 
> - Consolidate the testing if a device node may be opened in a new
>   function may_open_dev.
> 
> - Move the check for allowing access to device nodes on filesystems
>   not mounted in the initial user namespace from mount time to open
>   time and include it in may_open_dev.
> 
> This set of changes removes the implicit adding of MNT_NODEV which
> simplifies the logic in fs/namespace.c and removes a potentially
> problematic user visible difference in how normal and unprivileged
> mount namespaces work.
> 
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> ---
>  fs/block_dev.c     |  2 +-
>  fs/namei.c         |  9 ++++++++-
>  fs/namespace.c     | 18 ++++--------------
>  include/linux/fs.h |  1 +
>  4 files changed, 14 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 198243717da5..f8ce371c437c 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1729,7 +1729,7 @@ struct block_device *lookup_bdev(const char *pathname)
>  	if (!S_ISBLK(inode->i_mode))
>  		goto fail;
>  	error = -EACCES;
> -	if (path.mnt->mnt_flags & MNT_NODEV)
> +	if (!may_open_dev(&path))
>  		goto fail;
>  	error = -ENOMEM;
>  	bdev = bd_acquire(inode);
> diff --git a/fs/namei.c b/fs/namei.c
> index fbbcf0993312..59444c066f47 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2640,6 +2640,13 @@ int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
>  }
>  EXPORT_SYMBOL(vfs_create);
>  
> +bool may_open_dev(const struct path *path)
> +{
> +	return !(path->mnt->mnt_flags & MNT_NODEV) &&
> +		((path->mnt->mnt_sb->s_user_ns == &init_user_ns) ||
> +		 (path->mnt->mnt_sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT));
> +}
> +
>  static int may_open(struct path *path, int acc_mode, int flag)
>  {
>  	struct dentry *dentry = path->dentry;
> @@ -2662,7 +2669,7 @@ static int may_open(struct path *path, int acc_mode, int flag)
>  		break;
>  	case S_IFBLK:
>  	case S_IFCHR:
> -		if (path->mnt->mnt_flags & MNT_NODEV)
> +		if (!may_open_dev(path))
>  			return -EACCES;
>  		/*FALLTHRU*/
>  	case S_IFIFO:
> diff --git a/fs/namespace.c b/fs/namespace.c
> index d023a353dc63..e48fa1c23378 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2177,13 +2177,7 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
>  	}
>  	if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
>  	    !(mnt_flags & MNT_NODEV)) {
> -		/* Was the nodev implicitly added in mount? */
> -		if ((mnt->mnt_ns->user_ns != &init_user_ns) &&
> -		    !(sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT)) {
> -			mnt_flags |= MNT_NODEV;
> -		} else {
> -			return -EPERM;
> -		}
> +		return -EPERM;
>  	}
>  	if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) &&
>  	    !(mnt_flags & MNT_NOSUID)) {
> @@ -2396,13 +2390,6 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
>  			put_filesystem(type);
>  			return -EPERM;
>  		}
> -		/* Only in special cases allow devices from mounts
> -		 * created outside the initial user namespace.
> -		 */
> -		if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
> -			flags |= MS_NODEV;
> -			mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
> -		}
>  		if (type->fs_flags & FS_USERNS_VISIBLE) {
>  			if (!fs_fully_visible(type, &mnt_flags))
>  				return -EPERM;
> @@ -3238,6 +3225,9 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
>  		mnt_flags = mnt->mnt.mnt_flags;
>  		if (mnt->mnt.mnt_sb->s_iflags & SB_I_NOEXEC)
>  			mnt_flags &= ~(MNT_LOCK_NOSUID | MNT_LOCK_NOEXEC);
> +		if (current_user_ns() != &init_user_ns &&
> +		    !(mnt->mnt.mnt_sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT))
> +			mnt_flags &= ~(MNT_LOCK_NODEV);

Oops, this should be s_user_ns and not current_user_ns(). I think I had
to change it when I had made changes to make sysfs, etc. use s_user_ns =
&init_user_ns and then frogot to change it back.

Seth
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web