xref: /linux/fs/attr.c (revision 0a3a98f6dd4e8f4d928a09302c0d1c56f2192ac3)
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/smp_lock.h>
13 #include <linux/fsnotify.h>
14 #include <linux/fcntl.h>
15 #include <linux/quotaops.h>
16 #include <linux/security.h>
17 #include <linux/time.h>
18 
19 /* Taken over from the old code... */
20 
21 /* POSIX UID/GID verification for setting inode attributes. */
22 int inode_change_ok(struct inode *inode, struct iattr *attr)
23 {
24 	int retval = -EPERM;
25 	unsigned int ia_valid = attr->ia_valid;
26 
27 	/* If force is set do it anyway. */
28 	if (ia_valid & ATTR_FORCE)
29 		goto fine;
30 
31 	/* Make sure a caller can chown. */
32 	if ((ia_valid & ATTR_UID) &&
33 	    (current->fsuid != inode->i_uid ||
34 	     attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
35 		goto error;
36 
37 	/* Make sure caller can chgrp. */
38 	if ((ia_valid & ATTR_GID) &&
39 	    (current->fsuid != inode->i_uid ||
40 	    (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) &&
41 	    !capable(CAP_CHOWN))
42 		goto error;
43 
44 	/* Make sure a caller can chmod. */
45 	if (ia_valid & ATTR_MODE) {
46 		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
47 			goto error;
48 		/* Also check the setgid bit! */
49 		if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
50 				inode->i_gid) && !capable(CAP_FSETID))
51 			attr->ia_mode &= ~S_ISGID;
52 	}
53 
54 	/* Check for setting the inode time. */
55 	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
56 		if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
57 			goto error;
58 	}
59 fine:
60 	retval = 0;
61 error:
62 	return retval;
63 }
64 
65 EXPORT_SYMBOL(inode_change_ok);
66 
67 int inode_setattr(struct inode * inode, struct iattr * attr)
68 {
69 	unsigned int ia_valid = attr->ia_valid;
70 
71 	if (ia_valid & ATTR_SIZE &&
72 	    attr->ia_size != i_size_read(inode)) {
73 		int error = vmtruncate(inode, attr->ia_size);
74 		if (error)
75 			return error;
76 	}
77 
78 	if (ia_valid & ATTR_UID)
79 		inode->i_uid = attr->ia_uid;
80 	if (ia_valid & ATTR_GID)
81 		inode->i_gid = attr->ia_gid;
82 	if (ia_valid & ATTR_ATIME)
83 		inode->i_atime = timespec_trunc(attr->ia_atime,
84 						inode->i_sb->s_time_gran);
85 	if (ia_valid & ATTR_MTIME)
86 		inode->i_mtime = timespec_trunc(attr->ia_mtime,
87 						inode->i_sb->s_time_gran);
88 	if (ia_valid & ATTR_CTIME)
89 		inode->i_ctime = timespec_trunc(attr->ia_ctime,
90 						inode->i_sb->s_time_gran);
91 	if (ia_valid & ATTR_MODE) {
92 		umode_t mode = attr->ia_mode;
93 
94 		if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
95 			mode &= ~S_ISGID;
96 		inode->i_mode = mode;
97 	}
98 	mark_inode_dirty(inode);
99 
100 	return 0;
101 }
102 EXPORT_SYMBOL(inode_setattr);
103 
104 int notify_change(struct dentry * dentry, struct iattr * attr)
105 {
106 	struct inode *inode = dentry->d_inode;
107 	mode_t mode;
108 	int error;
109 	struct timespec now;
110 	unsigned int ia_valid = attr->ia_valid;
111 
112 	mode = inode->i_mode;
113 	now = current_fs_time(inode->i_sb);
114 
115 	attr->ia_ctime = now;
116 	if (!(ia_valid & ATTR_ATIME_SET))
117 		attr->ia_atime = now;
118 	if (!(ia_valid & ATTR_MTIME_SET))
119 		attr->ia_mtime = now;
120 	if (ia_valid & ATTR_KILL_SUID) {
121 		attr->ia_valid &= ~ATTR_KILL_SUID;
122 		if (mode & S_ISUID) {
123 			if (!(ia_valid & ATTR_MODE)) {
124 				ia_valid = attr->ia_valid |= ATTR_MODE;
125 				attr->ia_mode = inode->i_mode;
126 			}
127 			attr->ia_mode &= ~S_ISUID;
128 		}
129 	}
130 	if (ia_valid & ATTR_KILL_SGID) {
131 		attr->ia_valid &= ~ ATTR_KILL_SGID;
132 		if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
133 			if (!(ia_valid & ATTR_MODE)) {
134 				ia_valid = attr->ia_valid |= ATTR_MODE;
135 				attr->ia_mode = inode->i_mode;
136 			}
137 			attr->ia_mode &= ~S_ISGID;
138 		}
139 	}
140 	if (!attr->ia_valid)
141 		return 0;
142 
143 	if (ia_valid & ATTR_SIZE)
144 		down_write(&dentry->d_inode->i_alloc_sem);
145 
146 	if (inode->i_op && inode->i_op->setattr) {
147 		error = security_inode_setattr(dentry, attr);
148 		if (!error)
149 			error = inode->i_op->setattr(dentry, attr);
150 	} else {
151 		error = inode_change_ok(inode, attr);
152 		if (!error)
153 			error = security_inode_setattr(dentry, attr);
154 		if (!error) {
155 			if ((ia_valid & ATTR_UID && attr->ia_uid != inode->i_uid) ||
156 			    (ia_valid & ATTR_GID && attr->ia_gid != inode->i_gid))
157 				error = DQUOT_TRANSFER(inode, attr) ? -EDQUOT : 0;
158 			if (!error)
159 				error = inode_setattr(inode, attr);
160 		}
161 	}
162 
163 	if (ia_valid & ATTR_SIZE)
164 		up_write(&dentry->d_inode->i_alloc_sem);
165 
166 	if (!error)
167 		fsnotify_change(dentry, ia_valid);
168 
169 	return error;
170 }
171 
172 EXPORT_SYMBOL(notify_change);
173