Root/fs/attr.c

1/*
2 * linux/fs/attr.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * changes by Thomas Schoebel-Theuer
6 */
7
8#include <linux/module.h>
9#include <linux/time.h>
10#include <linux/mm.h>
11#include <linux/string.h>
12#include <linux/capability.h>
13#include <linux/fsnotify.h>
14#include <linux/fcntl.h>
15#include <linux/security.h>
16
17/* Taken over from the old code... */
18
19/* POSIX UID/GID verification for setting inode attributes. */
20int inode_change_ok(const struct inode *inode, struct iattr *attr)
21{
22    int retval = -EPERM;
23    unsigned int ia_valid = attr->ia_valid;
24
25    /* If force is set do it anyway. */
26    if (ia_valid & ATTR_FORCE)
27        goto fine;
28
29    /* Make sure a caller can chown. */
30    if ((ia_valid & ATTR_UID) &&
31        (current_fsuid() != inode->i_uid ||
32         attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
33        goto error;
34
35    /* Make sure caller can chgrp. */
36    if ((ia_valid & ATTR_GID) &&
37        (current_fsuid() != inode->i_uid ||
38        (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) &&
39        !capable(CAP_CHOWN))
40        goto error;
41
42    /* Make sure a caller can chmod. */
43    if (ia_valid & ATTR_MODE) {
44        if (!is_owner_or_cap(inode))
45            goto error;
46        /* Also check the setgid bit! */
47        if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
48                inode->i_gid) && !capable(CAP_FSETID))
49            attr->ia_mode &= ~S_ISGID;
50    }
51
52    /* Check for setting the inode time. */
53    if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
54        if (!is_owner_or_cap(inode))
55            goto error;
56    }
57fine:
58    retval = 0;
59error:
60    return retval;
61}
62EXPORT_SYMBOL(inode_change_ok);
63
64/**
65 * inode_newsize_ok - may this inode be truncated to a given size
66 * @inode: the inode to be truncated
67 * @offset: the new size to assign to the inode
68 * @Returns: 0 on success, -ve errno on failure
69 *
70 * inode_newsize_ok will check filesystem limits and ulimits to check that the
71 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
72 * when necessary. Caller must not proceed with inode size change if failure is
73 * returned. @inode must be a file (not directory), with appropriate
74 * permissions to allow truncate (inode_newsize_ok does NOT check these
75 * conditions).
76 *
77 * inode_newsize_ok must be called with i_mutex held.
78 */
79int inode_newsize_ok(const struct inode *inode, loff_t offset)
80{
81    if (inode->i_size < offset) {
82        unsigned long limit;
83
84        limit = rlimit(RLIMIT_FSIZE);
85        if (limit != RLIM_INFINITY && offset > limit)
86            goto out_sig;
87        if (offset > inode->i_sb->s_maxbytes)
88            goto out_big;
89    } else {
90        /*
91         * truncation of in-use swapfiles is disallowed - it would
92         * cause subsequent swapout to scribble on the now-freed
93         * blocks.
94         */
95        if (IS_SWAPFILE(inode))
96            return -ETXTBSY;
97    }
98
99    return 0;
100out_sig:
101    send_sig(SIGXFSZ, current, 0);
102out_big:
103    return -EFBIG;
104}
105EXPORT_SYMBOL(inode_newsize_ok);
106
107int inode_setattr(struct inode * inode, struct iattr * attr)
108{
109    unsigned int ia_valid = attr->ia_valid;
110
111    if (ia_valid & ATTR_SIZE &&
112        attr->ia_size != i_size_read(inode)) {
113        int error = vmtruncate(inode, attr->ia_size);
114        if (error)
115            return error;
116    }
117
118    if (ia_valid & ATTR_UID)
119        inode->i_uid = attr->ia_uid;
120    if (ia_valid & ATTR_GID)
121        inode->i_gid = attr->ia_gid;
122    if (ia_valid & ATTR_ATIME)
123        inode->i_atime = timespec_trunc(attr->ia_atime,
124                        inode->i_sb->s_time_gran);
125    if (ia_valid & ATTR_MTIME)
126        inode->i_mtime = timespec_trunc(attr->ia_mtime,
127                        inode->i_sb->s_time_gran);
128    if (ia_valid & ATTR_CTIME)
129        inode->i_ctime = timespec_trunc(attr->ia_ctime,
130                        inode->i_sb->s_time_gran);
131    if (ia_valid & ATTR_MODE) {
132        umode_t mode = attr->ia_mode;
133
134        if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
135            mode &= ~S_ISGID;
136        inode->i_mode = mode;
137    }
138    mark_inode_dirty(inode);
139
140    return 0;
141}
142EXPORT_SYMBOL(inode_setattr);
143
144int notify_change(struct dentry * dentry, struct iattr * attr)
145{
146    struct inode *inode = dentry->d_inode;
147    mode_t mode = inode->i_mode;
148    int error;
149    struct timespec now;
150    unsigned int ia_valid = attr->ia_valid;
151
152    if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
153        if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
154            return -EPERM;
155    }
156
157    now = current_fs_time(inode->i_sb);
158
159    attr->ia_ctime = now;
160    if (!(ia_valid & ATTR_ATIME_SET))
161        attr->ia_atime = now;
162    if (!(ia_valid & ATTR_MTIME_SET))
163        attr->ia_mtime = now;
164    if (ia_valid & ATTR_KILL_PRIV) {
165        attr->ia_valid &= ~ATTR_KILL_PRIV;
166        ia_valid &= ~ATTR_KILL_PRIV;
167        error = security_inode_need_killpriv(dentry);
168        if (error > 0)
169            error = security_inode_killpriv(dentry);
170        if (error)
171            return error;
172    }
173
174    /*
175     * We now pass ATTR_KILL_S*ID to the lower level setattr function so
176     * that the function has the ability to reinterpret a mode change
177     * that's due to these bits. This adds an implicit restriction that
178     * no function will ever call notify_change with both ATTR_MODE and
179     * ATTR_KILL_S*ID set.
180     */
181    if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
182        (ia_valid & ATTR_MODE))
183        BUG();
184
185    if (ia_valid & ATTR_KILL_SUID) {
186        if (mode & S_ISUID) {
187            ia_valid = attr->ia_valid |= ATTR_MODE;
188            attr->ia_mode = (inode->i_mode & ~S_ISUID);
189        }
190    }
191    if (ia_valid & ATTR_KILL_SGID) {
192        if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
193            if (!(ia_valid & ATTR_MODE)) {
194                ia_valid = attr->ia_valid |= ATTR_MODE;
195                attr->ia_mode = inode->i_mode;
196            }
197            attr->ia_mode &= ~S_ISGID;
198        }
199    }
200    if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
201        return 0;
202
203    error = security_inode_setattr(dentry, attr);
204    if (error)
205        return error;
206
207    if (ia_valid & ATTR_SIZE)
208        down_write(&dentry->d_inode->i_alloc_sem);
209
210    if (inode->i_op && inode->i_op->setattr) {
211        error = inode->i_op->setattr(dentry, attr);
212    } else {
213        error = inode_change_ok(inode, attr);
214        if (!error)
215            error = inode_setattr(inode, attr);
216    }
217
218    if (ia_valid & ATTR_SIZE)
219        up_write(&dentry->d_inode->i_alloc_sem);
220
221    if (!error)
222        fsnotify_change(dentry, ia_valid);
223
224    return error;
225}
226
227EXPORT_SYMBOL(notify_change);
228

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