1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
|
/* Copyright (C) 2005 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sysdep.h>
#include <stdlib.h>
#include <kernel-features.h>
/*
In Linux 2.1.x the chown functions have been changed. A new function lchown
was introduced. The new chown now follows symlinks - the old chown and the
new lchown do not follow symlinks.
This file emulates chown() under the old kernels.
*/
int
fchownat (int fd, const char *file, uid_t owner, gid_t group, int flag)
{
if (flag & ~AT_SYMLINK_NOFOLLOW)
{
__set_errno (EINVAL);
return -1;
}
char *buf = NULL;
if (fd != AT_FDCWD && file[0] != '/')
{
size_t filelen = strlen (file);
static const char procfd[] = "/proc/self/fd/%d/%s";
/* Buffer for the path name we are going to use. It consists of
- the string /proc/self/fd/
- the file descriptor number
- the file name provided.
The final NUL is included in the sizeof. A bit of overhead
due to the format elements compensates for possible negative
numbers. */
size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
buf = alloca (buflen);
__snprintf (buf, buflen, procfd, fd, file);
file = buf;
}
int result;
INTERNAL_SYSCALL_DECL (err);
#if __ASSUME_LCHOWN_SYSCALL
if (flag & AT_SYMLINK_NOFOLLOW)
result = INTERNAL_SYSCALL (lchown, err, 3, file, owner, group);
else
result = INTERNAL_SYSCALL (chown, err, 3, file, owner, group);
#else
char link[PATH_MAX + 2];
char path[2 * PATH_MAX + 4];
int loopct;
size_t filelen;
static int libc_old_chown = 0 /* -1=old linux, 1=new linux, 0=unknown */;
if (libc_old_chown == 1)
{
if (flag & AT_SYMLINK_NOFOLLOW)
result = INTERNAL_SYSCALL (lchown, err, 3, __ptrvalue (file), owner,
group);
else
result = INTERNAL_SYSCALL (chown, err, 3, __ptrvalue (file), owner,
group);
goto out;
}
# ifdef __NR_lchown
if (flag & AT_SYMLINK_NOFOLLOW)
{
result = INTERNAL_SYSCALL (lchown, err, 3, __ptrvalue (file), owner,
group);
goto out;
}
if (libc_old_chown == 0)
{
result = INTERNAL_SYSCALL (chown, err, 3, __ptrvalue (file), owner,
group);
if (__builtin_expect (!INTERNAL_SYSCALL_ERROR_P (result, err), 1))
return result;
if (INTERNAL_SYSCALL_ERRNO (result, err) != ENOSYS)
{
libc_old_chown = 1;
goto fail;
}
libc_old_chown = -1;
}
# else
if (flag & AT_SYMLINK_NOFOLLOW)
{
result = INTERNAL_SYSCALL (chown, err, 3, __ptrvalue (file), owner,
group);
goto out;
}
# endif
result = __readlink (file, link, PATH_MAX + 1);
if (result == -1)
{
# ifdef __NR_lchown
result = INTERNAL_SYSCALL (lchown, err, 3, __ptrvalue (file), owner,
group);
# else
result = INTERNAL_SYSCALL (chown, err, 3, __ptrvalue (file), owner,
group);
# endif
goto out;
}
filelen = strlen (file) + 1;
if (filelen > sizeof (path))
{
errno = ENAMETOOLONG;
return -1;
}
memcpy (path, file, filelen);
/* 'The system has an arbitrary limit...' In practise, we'll hit
ENAMETOOLONG before this, usually. */
for (loopct = 0; loopct < 128; ++loopct)
{
size_t linklen;
if (result >= PATH_MAX + 1)
{
errno = ENAMETOOLONG;
return -1;
}
link[result] = 0; /* Null-terminate string, just-in-case. */
linklen = strlen (link) + 1;
if (link[0] == '/')
memcpy (path, link, linklen);
else
{
filelen = strlen (path);
while (filelen > 1 && path[filelen - 1] == '/')
--filelen;
while (filelen > 0 && path[filelen - 1] != '/')
--filelen;
if (filelen + linklen > sizeof (path))
{
errno = ENAMETOOLONG;
return -1;
}
memcpy (path + filelen, link, linklen);
}
result = __readlink (path, link, PATH_MAX + 1);
if (result == -1)
{
# ifdef __NR_lchown
result = INTERNAL_SYSCALL (lchown, err, 3, path, owner, group);
# else
result = INTERNAL_SYSCALL (chown, err, 3, path, owner, group);
# endif
goto out;
}
}
__set_errno (ELOOP);
return -1;
out:
#endif
if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
{
#if !__ASSUME_LCHOWN_SYSCALL
fail:
#endif
__atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, buf);
result = -1;
}
return result;
}
|
