Commit 5de75970 authored by Hugh Dickins's avatar Hugh Dickins Committed by Christian Brauner
Browse files

xattr: simple_xattr_set() return old_xattr to be freed 



tmpfs wants to support limited user extended attributes, but kernfs
(or cgroupfs, the only kernfs with KERNFS_ROOT_SUPPORT_USER_XATTR)
already supports user extended attributes through simple xattrs: but
limited by a policy (128KiB per inode) too liberal to be used on tmpfs.

To allow a different limiting policy for tmpfs, without affecting the
policy for kernfs, change simple_xattr_set() to return the replaced or
removed xattr (if any), leaving the caller to update their accounting
then free the xattr (by simple_xattr_free(), renamed from the static
free_simple_xattr()).

Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarChristian Brauner <brauner@kernel.org>
Reviewed-by: default avatarCarlos Maiolino <cmaiolino@redhat.com>
Message-Id: <158c6585-2aa7-d4aa-90ff-f7c3f8fe407c@google.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 0200679f

fs/kernfs/inode.c

+29 −17
Original line number Diff line number Diff line
@@ -306,11 +306,17 @@ int kernfs_xattr_get(struct kernfs_node *kn, const char *name, 
int kernfs_xattr_set(struct kernfs_node *kn, const char *name,

		     const void *value, size_t size, int flags)

{

	struct simple_xattr *old_xattr;

	struct kernfs_iattrs *attrs = kernfs_iattrs(kn);

	if (!attrs)

		return -ENOMEM;



	return simple_xattr_set(&attrs->xattrs, name, value, size, flags, NULL);

	old_xattr = simple_xattr_set(&attrs->xattrs, name, value, size, flags);

	if (IS_ERR(old_xattr))

		return PTR_ERR(old_xattr);



	simple_xattr_free(old_xattr);

	return 0;

}



static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
@@ -342,7 +348,7 @@ static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn, 
{

	atomic_t *sz = &kn->iattr->user_xattr_size;

	atomic_t *nr = &kn->iattr->nr_user_xattrs;

	ssize_t removed_size;

	struct simple_xattr *old_xattr;

	int ret;



	if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) {
@@ -355,13 +361,18 @@ static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn, 
		goto dec_size_out;

	}



	ret = simple_xattr_set(xattrs, full_name, value, size, flags,

			       &removed_size);



	if (!ret && removed_size >= 0)

		size = removed_size;

	else if (!ret)

	old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags);

	if (!old_xattr)

		return 0;



	if (IS_ERR(old_xattr)) {

		ret = PTR_ERR(old_xattr);

		goto dec_size_out;

	}



	ret = 0;

	size = old_xattr->size;

	simple_xattr_free(old_xattr);

dec_size_out:

	atomic_sub(size, sz);

dec_count_out:
@@ -376,18 +387,19 @@ static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn, 
{

	atomic_t *sz = &kn->iattr->user_xattr_size;

	atomic_t *nr = &kn->iattr->nr_user_xattrs;

	ssize_t removed_size;

	int ret;

	struct simple_xattr *old_xattr;



	ret = simple_xattr_set(xattrs, full_name, value, size, flags,

			       &removed_size);

	old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags);

	if (!old_xattr)

		return 0;



	if (removed_size >= 0) {

		atomic_sub(removed_size, sz);

		atomic_dec(nr);

	}

	if (IS_ERR(old_xattr))

		return PTR_ERR(old_xattr);



	return ret;

	atomic_sub(old_xattr->size, sz);

	atomic_dec(nr);

	simple_xattr_free(old_xattr);

	return 0;

}



static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,

fs/xattr.c

+22 −29
Original line number Diff line number Diff line
@@ -1040,12 +1040,12 @@ const char *xattr_full_name(const struct xattr_handler *handler, 
EXPORT_SYMBOL(xattr_full_name);



/**

 * free_simple_xattr - free an xattr object

 * simple_xattr_free - free an xattr object

 * @xattr: the xattr object

 *

 * Free the xattr object. Can handle @xattr being NULL.

 */

static inline void free_simple_xattr(struct simple_xattr *xattr)

void simple_xattr_free(struct simple_xattr *xattr)

{

	if (xattr)

		kfree(xattr->name);
@@ -1164,7 +1164,6 @@ int simple_xattr_get(struct simple_xattrs *xattrs, const char *name, 
 * @value: the value to store along the xattr

 * @size: the size of @value

 * @flags: the flags determining how to set the xattr

 * @removed_size: the size of the removed xattr

 *

 * Set a new xattr object.

 * If @value is passed a new xattr object will be allocated. If XATTR_REPLACE
@@ -1181,29 +1180,27 @@ int simple_xattr_get(struct simple_xattrs *xattrs, const char *name, 
 * nothing if XATTR_CREATE is specified in @flags or @flags is zero. For

 * XATTR_REPLACE we fail as mentioned above.

 *

 * Return: On success zero and on error a negative error code is returned.

 * Return: On success, the removed or replaced xattr is returned, to be freed

 * by the caller; or NULL if none. On failure a negative error code is returned.

 */

int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,

		     const void *value, size_t size, int flags,

		     ssize_t *removed_size)

struct simple_xattr *simple_xattr_set(struct simple_xattrs *xattrs,

				      const char *name, const void *value,

				      size_t size, int flags)

{

	struct simple_xattr *xattr = NULL, *new_xattr = NULL;

	struct simple_xattr *old_xattr = NULL, *new_xattr = NULL;

	struct rb_node *parent = NULL, **rbp;

	int err = 0, ret;



	if (removed_size)

		*removed_size = -1;



	/* value == NULL means remove */

	if (value) {

		new_xattr = simple_xattr_alloc(value, size);

		if (!new_xattr)

			return -ENOMEM;

			return ERR_PTR(-ENOMEM);



		new_xattr->name = kstrdup(name, GFP_KERNEL);

		if (!new_xattr->name) {

			free_simple_xattr(new_xattr);

			return -ENOMEM;

			simple_xattr_free(new_xattr);

			return ERR_PTR(-ENOMEM);

		}

	}
@@ -1217,12 +1214,12 @@ int simple_xattr_set(struct simple_xattrs *xattrs, const char *name, 
		else if (ret > 0)

			rbp = &(*rbp)->rb_right;

		else

			xattr = rb_entry(*rbp, struct simple_xattr, rb_node);

		if (xattr)

			old_xattr = rb_entry(*rbp, struct simple_xattr, rb_node);

		if (old_xattr)

			break;

	}



	if (xattr) {

	if (old_xattr) {

		/* Fail if XATTR_CREATE is requested and the xattr exists. */

		if (flags & XATTR_CREATE) {

			err = -EEXIST;
@@ -1230,12 +1227,10 @@ int simple_xattr_set(struct simple_xattrs *xattrs, const char *name, 
		}



		if (new_xattr)

			rb_replace_node(&xattr->rb_node, &new_xattr->rb_node,

					&xattrs->rb_root);

			rb_replace_node(&old_xattr->rb_node,

					&new_xattr->rb_node, &xattrs->rb_root);

		else

			rb_erase(&xattr->rb_node, &xattrs->rb_root);

		if (!err && removed_size)

			*removed_size = xattr->size;

			rb_erase(&old_xattr->rb_node, &xattrs->rb_root);

	} else {

		/* Fail if XATTR_REPLACE is requested but no xattr is found. */

		if (flags & XATTR_REPLACE) {
@@ -1260,12 +1255,10 @@ int simple_xattr_set(struct simple_xattrs *xattrs, const char *name, 


out_unlock:

	write_unlock(&xattrs->lock);

	if (err)

		free_simple_xattr(new_xattr);

	else

		free_simple_xattr(xattr);

	return err;



	if (!err)

		return old_xattr;

	simple_xattr_free(new_xattr);

	return ERR_PTR(err);

}



static bool xattr_is_trusted(const char *name)
@@ -1386,7 +1379,7 @@ void simple_xattrs_free(struct simple_xattrs *xattrs) 
		rbp_next = rb_next(rbp);

		xattr = rb_entry(rbp, struct simple_xattr, rb_node);

		rb_erase(&xattr->rb_node, &xattrs->rb_root);

		free_simple_xattr(xattr);

		simple_xattr_free(xattr);

		rbp = rbp_next;

	}

}

include/linux/xattr.h

+4 −3
Original line number Diff line number Diff line
@@ -116,11 +116,12 @@ struct simple_xattr { 
void simple_xattrs_init(struct simple_xattrs *xattrs);

void simple_xattrs_free(struct simple_xattrs *xattrs);

struct simple_xattr *simple_xattr_alloc(const void *value, size_t size);

void simple_xattr_free(struct simple_xattr *xattr);

int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,

		     void *buffer, size_t size);

int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,

		     const void *value, size_t size, int flags,

		     ssize_t *removed_size);

struct simple_xattr *simple_xattr_set(struct simple_xattrs *xattrs,

				      const char *name, const void *value,

				      size_t size, int flags);

ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,

			  char *buffer, size_t size);

void simple_xattr_add(struct simple_xattrs *xattrs,

mm/shmem.c

+6 −4
Original line number Diff line number Diff line
@@ -3598,15 +3598,17 @@ static int shmem_xattr_handler_set(const struct xattr_handler *handler, 
				   size_t size, int flags)

{

	struct shmem_inode_info *info = SHMEM_I(inode);

	int err;

	struct simple_xattr *old_xattr;



	name = xattr_full_name(handler, name);

	err = simple_xattr_set(&info->xattrs, name, value, size, flags, NULL);

	if (!err) {

	old_xattr = simple_xattr_set(&info->xattrs, name, value, size, flags);

	if (!IS_ERR(old_xattr)) {

		simple_xattr_free(old_xattr);

		old_xattr = NULL;

		inode->i_ctime = current_time(inode);

		inode_inc_iversion(inode);

	}

	return err;

	return PTR_ERR(old_xattr);

}



static const struct xattr_handler shmem_security_xattr_handler = {