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![Andreas Gruenbacher](/assets/img/avatar_default.png)
The patches solve the following problem: We want to grant access to devices based on who is logged in from where, etc. This includes switching back and forth between multiple user sessions, etc. Using ACLs to define device access for logged-in users gives us all the flexibility we need in order to fully solve the problem. Device special files nowadays usually live on tmpfs, hence tmpfs ACLs. Different distros have come up with solutions that solve the problem to different degrees: SUSE uses a resource manager which tracks login sessions and sets ACLs on device inodes as appropriate. RedHat uses pam_console, which changes the primary file ownership to the logged-in user. Others use a set of groups that users must be in in order to be granted the appropriate accesses. The freedesktop.org project plans to implement a combination of a console-tracker and a HAL-device-list based solution to grant access to devices to users, and more distros will likely follow this approach. These patches have first been posted here on 2 February 2005, and again on 8 January 2006. We have been shipping them in SLES9 and SLES10 with no problems reported. The previous submission is archived here: http://lkml.org/lkml/2006/1/8/229 http://lkml.org/lkml/2006/1/8/230 http://lkml.org/lkml/2006/1/8/231 This patch: Add some infrastructure for access control lists on in-memory filesystems such as tmpfs. Signed-off-by: Andreas Gruenbacher <agruen@suse.de> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
197 lines
4.2 KiB
C
197 lines
4.2 KiB
C
/*
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* fs/generic_acl.c
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*
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* (C) 2005 Andreas Gruenbacher <agruen@suse.de>
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*
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* This file is released under the GPL.
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*/
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#include <linux/sched.h>
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#include <linux/fs.h>
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#include <linux/generic_acl.h>
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/**
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* generic_acl_list - Generic xattr_handler->list() operation
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* @ops: Filesystem specific getacl and setacl callbacks
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*/
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size_t
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generic_acl_list(struct inode *inode, struct generic_acl_operations *ops,
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int type, char *list, size_t list_size)
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{
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struct posix_acl *acl;
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const char *name;
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size_t size;
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acl = ops->getacl(inode, type);
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if (!acl)
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return 0;
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posix_acl_release(acl);
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switch(type) {
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case ACL_TYPE_ACCESS:
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name = POSIX_ACL_XATTR_ACCESS;
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break;
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case ACL_TYPE_DEFAULT:
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name = POSIX_ACL_XATTR_DEFAULT;
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break;
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default:
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return 0;
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}
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size = strlen(name) + 1;
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if (list && size <= list_size)
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memcpy(list, name, size);
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return size;
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}
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/**
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* generic_acl_get - Generic xattr_handler->get() operation
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* @ops: Filesystem specific getacl and setacl callbacks
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*/
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int
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generic_acl_get(struct inode *inode, struct generic_acl_operations *ops,
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int type, void *buffer, size_t size)
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{
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struct posix_acl *acl;
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int error;
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acl = ops->getacl(inode, type);
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if (!acl)
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return -ENODATA;
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error = posix_acl_to_xattr(acl, buffer, size);
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posix_acl_release(acl);
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return error;
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}
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/**
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* generic_acl_set - Generic xattr_handler->set() operation
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* @ops: Filesystem specific getacl and setacl callbacks
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*/
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int
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generic_acl_set(struct inode *inode, struct generic_acl_operations *ops,
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int type, const void *value, size_t size)
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{
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struct posix_acl *acl = NULL;
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int error;
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if (S_ISLNK(inode->i_mode))
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return -EOPNOTSUPP;
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if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
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return -EPERM;
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if (value) {
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acl = posix_acl_from_xattr(value, size);
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if (IS_ERR(acl))
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return PTR_ERR(acl);
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}
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if (acl) {
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mode_t mode;
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error = posix_acl_valid(acl);
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if (error)
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goto failed;
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switch(type) {
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case ACL_TYPE_ACCESS:
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mode = inode->i_mode;
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error = posix_acl_equiv_mode(acl, &mode);
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if (error < 0)
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goto failed;
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inode->i_mode = mode;
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if (error == 0) {
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posix_acl_release(acl);
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acl = NULL;
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}
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break;
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case ACL_TYPE_DEFAULT:
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if (!S_ISDIR(inode->i_mode)) {
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error = -EINVAL;
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goto failed;
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}
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break;
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}
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}
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ops->setacl(inode, type, acl);
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error = 0;
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failed:
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posix_acl_release(acl);
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return error;
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}
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/**
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* generic_acl_init - Take care of acl inheritance at @inode create time
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* @ops: Filesystem specific getacl and setacl callbacks
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*
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* Files created inside a directory with a default ACL inherit the
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* directory's default ACL.
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*/
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int
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generic_acl_init(struct inode *inode, struct inode *dir,
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struct generic_acl_operations *ops)
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{
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struct posix_acl *acl = NULL;
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mode_t mode = inode->i_mode;
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int error;
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inode->i_mode = mode & ~current->fs->umask;
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if (!S_ISLNK(inode->i_mode))
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acl = ops->getacl(dir, ACL_TYPE_DEFAULT);
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if (acl) {
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struct posix_acl *clone;
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if (S_ISDIR(inode->i_mode)) {
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clone = posix_acl_clone(acl, GFP_KERNEL);
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error = -ENOMEM;
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if (!clone)
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goto cleanup;
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ops->setacl(inode, ACL_TYPE_DEFAULT, clone);
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posix_acl_release(clone);
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}
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clone = posix_acl_clone(acl, GFP_KERNEL);
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error = -ENOMEM;
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if (!clone)
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goto cleanup;
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error = posix_acl_create_masq(clone, &mode);
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if (error >= 0) {
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inode->i_mode = mode;
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if (error > 0)
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ops->setacl(inode, ACL_TYPE_ACCESS, clone);
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}
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posix_acl_release(clone);
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}
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error = 0;
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cleanup:
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posix_acl_release(acl);
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return error;
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}
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/**
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* generic_acl_chmod - change the access acl of @inode upon chmod()
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* @ops: FIlesystem specific getacl and setacl callbacks
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*
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* A chmod also changes the permissions of the owner, group/mask, and
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* other ACL entries.
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*/
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int
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generic_acl_chmod(struct inode *inode, struct generic_acl_operations *ops)
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{
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struct posix_acl *acl, *clone;
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int error = 0;
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if (S_ISLNK(inode->i_mode))
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return -EOPNOTSUPP;
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acl = ops->getacl(inode, ACL_TYPE_ACCESS);
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if (acl) {
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clone = posix_acl_clone(acl, GFP_KERNEL);
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posix_acl_release(acl);
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if (!clone)
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return -ENOMEM;
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error = posix_acl_chmod_masq(clone, inode->i_mode);
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if (!error)
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ops->setacl(inode, ACL_TYPE_ACCESS, clone);
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posix_acl_release(clone);
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}
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return error;
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}
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