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sysfs: add sysfs_link_change_owner()

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Add a helper to change the owner of a sysfs link.
This function will be used to correctly account for kobject ownership
changes, e.g. when moving network devices between network namespaces.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Christian Brauner 2020-02-27 04:37:12 +01:00 committed by David S. Miller
parent f70ce18568
commit 0666a3aee7
2 changed files with 51 additions and 0 deletions
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41
fs/sysfs/file.c
View File

@ -570,6 +570,47 @@ static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
return kernfs_setattr(kn, &newattrs);
}
/**
* sysfs_link_change_owner - change owner of a sysfs file.
* @kobj: object of the kernfs_node the symlink is located in.
* @targ: object of the kernfs_node the symlink points to.
* @name: name of the link.
* @kuid: new owner's kuid
* @kgid: new owner's kgid
*
* This function looks up the sysfs symlink entry @name under @kobj and changes
* the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
* @targ.
*
* Returns 0 on success or error code on failure.
*/
int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
const char *name, kuid_t kuid, kgid_t kgid)
{
struct kernfs_node *kn = NULL;
int error;
if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
return -EINVAL;
error = -ENOENT;
kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
if (!kn)
goto out;
error = -EINVAL;
if (kernfs_type(kn) != KERNFS_LINK)
goto out;
if (kn->symlink.target_kn->priv != targ)
goto out;
error = internal_change_owner(kn, kuid, kgid);
out:
kernfs_put(kn);
return error;
}
/**
* sysfs_file_change_owner - change owner of a sysfs file.
* @kobj: object.

10
include/linux/sysfs.h
View File

@ -312,6 +312,8 @@ static inline void sysfs_enable_ns(struct kernfs_node *kn)
int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
kgid_t kgid);
int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
const char *name, kuid_t kuid, kgid_t kgid);
#else /* CONFIG_SYSFS */
@ -532,6 +534,14 @@ static inline int sysfs_file_change_owner(struct kobject *kobj,
return 0;
}
static inline int sysfs_link_change_owner(struct kobject *kobj,
struct kobject *targ,
const char *name, kuid_t kuid,
kgid_t kgid)
{
return 0;
}
#endif /* CONFIG_SYSFS */
static inline int __must_check sysfs_create_file(struct kobject *kobj,