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Commit 132e4608 authored by David Howells's avatar David Howells Committed by Al Viro
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new helper: do_new_mount_fc() 



Create an fs_context-aware version of do_new_mount().  This takes an
fs_context with a superblock already attached to it.

Make do_new_mount() use do_new_mount_fc() rather than do_new_mount(); this
allows the consolidation of the mount creation, check and add steps.

To make this work, mount_too_revealing() is changed to take a superblock
rather than a mount (which the fs_context doesn't have available), allowing
this check to be done before the mount object is created.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Co-developed-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent a0c9a8b8

fs/namespace.c

+39 −26
Original line number Diff line number Diff line
@@ -2523,7 +2523,37 @@ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) 
	return err;

}



static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags);

static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);



/*

 * Create a new mount using a superblock configuration and request it

 * be added to the namespace tree.

 */

static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,

			   unsigned int mnt_flags)

{

	struct vfsmount *mnt;

	struct super_block *sb = fc->root->d_sb;

	int error;



	if (mount_too_revealing(sb, &mnt_flags)) {

		dput(fc->root);

		fc->root = NULL;

		deactivate_locked_super(sb);

		return -EPERM;

	}



	up_write(&sb->s_umount);



	mnt = vfs_create_mount(fc);

	if (IS_ERR(mnt))

		return PTR_ERR(mnt);



	error = do_add_mount(real_mount(mnt), mountpoint, mnt_flags);

	if (error < 0)

		mntput(mnt);

	return error;

}



/*

 * create a new mount for userspace and request it to be added into the
@@ -2533,7 +2563,6 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags, 
			int mnt_flags, const char *name, void *data)

{

	struct file_system_type *type;

	struct vfsmount *mnt;

	struct fs_context *fc;

	const char *subtype = NULL;

	int err = 0;
@@ -2577,26 +2606,9 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags, 
		err = parse_monolithic_mount_data(fc, data);

	if (!err)

		err = vfs_get_tree(fc);

	if (err)

		goto out;



	up_write(&fc->root->d_sb->s_umount);

	mnt = vfs_create_mount(fc);

	if (IS_ERR(mnt)) {

		err = PTR_ERR(mnt);

		goto out;

	}



	if (mount_too_revealing(mnt, &mnt_flags)) {

		mntput(mnt);

		err = -EPERM;

		goto out;

	}

	if (!err)

		err = do_new_mount_fc(fc, path, mnt_flags);



	err = do_add_mount(real_mount(mnt), path, mnt_flags);

	if (err)

		mntput(mnt);

out:

	put_fs_context(fc);

	return err;

}
@@ -3421,7 +3433,8 @@ bool current_chrooted(void) 
	return chrooted;

}



static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new,

static bool mnt_already_visible(struct mnt_namespace *ns,

				const struct super_block *sb,

				int *new_mnt_flags)

{

	int new_flags = *new_mnt_flags;
@@ -3433,7 +3446,7 @@ static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new, 
		struct mount *child;

		int mnt_flags;



		if (mnt->mnt.mnt_sb->s_type != new->mnt_sb->s_type)

		if (mnt->mnt.mnt_sb->s_type != sb->s_type)

			continue;



		/* This mount is not fully visible if it's root directory
@@ -3484,7 +3497,7 @@ static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new, 
	return visible;

}



static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags)

static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)

{

	const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;

	struct mnt_namespace *ns = current->nsproxy->mnt_ns;
@@ -3494,7 +3507,7 @@ static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags) 
		return false;



	/* Can this filesystem be too revealing? */

	s_iflags = mnt->mnt_sb->s_iflags;

	s_iflags = sb->s_iflags;

	if (!(s_iflags & SB_I_USERNS_VISIBLE))

		return false;
@@ -3504,7 +3517,7 @@ static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags) 
		return true;

	}



	return !mnt_already_visible(ns, mnt, new_mnt_flags);

	return !mnt_already_visible(ns, sb, new_mnt_flags);

}



bool mnt_may_suid(struct vfsmount *mnt)