Commit 0b52075e authored by Al Viro's avatar Al Viro
Browse files

introduce cloning of fs_context 



new primitive: vfs_dup_fs_context().  Comes with fs_context
method (->dup()) for copying the filesystem-specific parts
of fs_context, along with LSM one (->fs_context_dup()) for
doing the same to LSM parts.

[needs better commit message, and change of Author:, anyway]

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent cb50b348

fs/fs_context.c

+67 −0
Original line number Diff line number Diff line
@@ -337,6 +337,47 @@ void fc_drop_locked(struct fs_context *fc) 


static void legacy_fs_context_free(struct fs_context *fc);



/**

 * vfs_dup_fc_config: Duplicate a filesystem context.

 * @src_fc: The context to copy.

 */

struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)

{

	struct fs_context *fc;

	int ret;



	if (!src_fc->ops->dup)

		return ERR_PTR(-EOPNOTSUPP);



	fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL);

	if (!fc)

		return ERR_PTR(-ENOMEM);



	fc->fs_private	= NULL;

	fc->s_fs_info	= NULL;

	fc->source	= NULL;

	fc->security	= NULL;

	get_filesystem(fc->fs_type);

	get_net(fc->net_ns);

	get_user_ns(fc->user_ns);

	get_cred(fc->cred);



	/* Can't call put until we've called ->dup */

	ret = fc->ops->dup(fc, src_fc);

	if (ret < 0)

		goto err_fc;



	ret = security_fs_context_dup(fc, src_fc);

	if (ret < 0)

		goto err_fc;

	return fc;



err_fc:

	put_fs_context(fc);

	return ERR_PTR(ret);

}

EXPORT_SYMBOL(vfs_dup_fs_context);



/**

 * put_fs_context - Dispose of a superblock configuration context.

 * @fc: The context to dispose of.
@@ -380,6 +421,31 @@ static void legacy_fs_context_free(struct fs_context *fc) 
	}

}



/*

 * Duplicate a legacy config.

 */

static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)

{

	struct legacy_fs_context *ctx;

	struct legacy_fs_context *src_ctx = src_fc->fs_private;



	ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);

	if (!ctx)

		return -ENOMEM;



	if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {

		ctx->legacy_data = kmemdup(src_ctx->legacy_data,

					   src_ctx->data_size, GFP_KERNEL);

		if (!ctx->legacy_data) {

			kfree(ctx);

			return -ENOMEM;

		}

	}



	fc->fs_private = ctx;

	return 0;

}



/*

 * Add a parameter to a legacy config.  We build up a comma-separated list of

 * options.
@@ -514,6 +580,7 @@ static int legacy_reconfigure(struct fs_context *fc) 


const struct fs_context_operations legacy_fs_context_ops = {

	.free			= legacy_fs_context_free,

	.dup			= legacy_fs_context_dup,

	.parse_param		= legacy_parse_param,

	.parse_monolithic	= legacy_parse_monolithic,

	.get_tree		= legacy_get_tree,

include/linux/fs_context.h

+2 −0
Original line number Diff line number Diff line
@@ -94,6 +94,7 @@ struct fs_context { 


struct fs_context_operations {

	void (*free)(struct fs_context *fc);

	int (*dup)(struct fs_context *fc, struct fs_context *src_fc);

	int (*parse_param)(struct fs_context *fc, struct fs_parameter *param);

	int (*parse_monolithic)(struct fs_context *fc, void *data);

	int (*get_tree)(struct fs_context *fc);
@@ -111,6 +112,7 @@ extern struct fs_context *fs_context_for_reconfigure(struct dentry *dentry, 
extern struct fs_context *fs_context_for_submount(struct file_system_type *fs_type,

						struct dentry *reference);



extern struct fs_context *vfs_dup_fs_context(struct fs_context *fc);

extern int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param);

extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,

			       const char *value, size_t v_size);

include/linux/lsm_hooks.h

+7 −0
Original line number Diff line number Diff line
@@ -79,6 +79,11 @@ 
 * Security hooks for mount using fs_context.

 *	[See also Documentation/filesystems/mounting.txt]

 *

 * @fs_context_dup:

 *	Allocate and attach a security structure to sc->security.  This pointer

 *	is initialised to NULL by the caller.

 *	@fc indicates the new filesystem context.

 *	@src_fc indicates the original filesystem context.

 * @fs_context_parse_param:

 *	Userspace provided a parameter to configure a superblock.  The LSM may

 *	reject it with an error and may use it for itself, in which case it
@@ -1470,6 +1475,7 @@ union security_list_options { 
	void (*bprm_committing_creds)(struct linux_binprm *bprm);

	void (*bprm_committed_creds)(struct linux_binprm *bprm);



	int (*fs_context_dup)(struct fs_context *fc, struct fs_context *src_sc);

	int (*fs_context_parse_param)(struct fs_context *fc, struct fs_parameter *param);



	int (*sb_alloc_security)(struct super_block *sb);
@@ -1813,6 +1819,7 @@ struct security_hook_heads { 
	struct hlist_head bprm_check_security;

	struct hlist_head bprm_committing_creds;

	struct hlist_head bprm_committed_creds;

	struct hlist_head fs_context_dup;

	struct hlist_head fs_context_parse_param;

	struct hlist_head sb_alloc_security;

	struct hlist_head sb_free_security;

include/linux/security.h

+6 −0
Original line number Diff line number Diff line
@@ -223,6 +223,7 @@ int security_bprm_set_creds(struct linux_binprm *bprm); 
int security_bprm_check(struct linux_binprm *bprm);

void security_bprm_committing_creds(struct linux_binprm *bprm);

void security_bprm_committed_creds(struct linux_binprm *bprm);

int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc);

int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *param);

int security_sb_alloc(struct super_block *sb);

void security_sb_free(struct super_block *sb);
@@ -521,6 +522,11 @@ static inline void security_bprm_committed_creds(struct linux_binprm *bprm) 
{

}



static inline int security_fs_context_dup(struct fs_context *fc,

					  struct fs_context *src_fc)

{

	return 0;

}

static inline int security_fs_context_parse_param(struct fs_context *fc,

						  struct fs_parameter *param)

{

security/security.c

+5 −0
Original line number Diff line number Diff line
@@ -374,6 +374,11 @@ void security_bprm_committed_creds(struct linux_binprm *bprm) 
	call_void_hook(bprm_committed_creds, bprm);

}



int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)

{

	return call_int_hook(fs_context_dup, 0, fc, src_fc);

}



int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *param)

{

	return call_int_hook(fs_context_parse_param, -ENOPARAM, fc, param);