copy_signal() cleanup: clean tty_audit_fork()
[linux-2.6.git] / drivers / char / tty_audit.c
1 /*
2  * Creating audit events from TTY input.
3  *
4  * Copyright (C) 2007 Red Hat, Inc.  All rights reserved.  This copyrighted
5  * material is made available to anyone wishing to use, modify, copy, or
6  * redistribute it subject to the terms and conditions of the GNU General
7  * Public License v.2.
8  *
9  * Authors: Miloslav Trmac <mitr@redhat.com>
10  */
11
12 #include <linux/audit.h>
13 #include <linux/tty.h>
14
15 struct tty_audit_buf {
16         atomic_t count;
17         struct mutex mutex;     /* Protects all data below */
18         int major, minor;       /* The TTY which the data is from */
19         unsigned icanon:1;
20         size_t valid;
21         unsigned char *data;    /* Allocated size N_TTY_BUF_SIZE */
22 };
23
24 static struct tty_audit_buf *tty_audit_buf_alloc(int major, int minor,
25                                                  int icanon)
26 {
27         struct tty_audit_buf *buf;
28
29         buf = kmalloc(sizeof(*buf), GFP_KERNEL);
30         if (!buf)
31                 goto err;
32         buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
33         if (!buf->data)
34                 goto err_buf;
35         atomic_set(&buf->count, 1);
36         mutex_init(&buf->mutex);
37         buf->major = major;
38         buf->minor = minor;
39         buf->icanon = icanon;
40         buf->valid = 0;
41         return buf;
42
43 err_buf:
44         kfree(buf);
45 err:
46         return NULL;
47 }
48
49 static void tty_audit_buf_free(struct tty_audit_buf *buf)
50 {
51         WARN_ON(buf->valid != 0);
52         kfree(buf->data);
53         kfree(buf);
54 }
55
56 static void tty_audit_buf_put(struct tty_audit_buf *buf)
57 {
58         if (atomic_dec_and_test(&buf->count))
59                 tty_audit_buf_free(buf);
60 }
61
62 static void tty_audit_log(const char *description, struct task_struct *tsk,
63                           uid_t loginuid, unsigned sessionid, int major,
64                           int minor, unsigned char *data, size_t size)
65 {
66         struct audit_buffer *ab;
67
68         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
69         if (ab) {
70                 char name[sizeof(tsk->comm)];
71                 uid_t uid = task_uid(tsk);
72
73                 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u "
74                                  "major=%d minor=%d comm=", description,
75                                  tsk->pid, uid, loginuid, sessionid,
76                                  major, minor);
77                 get_task_comm(name, tsk);
78                 audit_log_untrustedstring(ab, name);
79                 audit_log_format(ab, " data=");
80                 audit_log_n_hex(ab, data, size);
81                 audit_log_end(ab);
82         }
83 }
84
85 /**
86  *      tty_audit_buf_push      -       Push buffered data out
87  *
88  *      Generate an audit message from the contents of @buf, which is owned by
89  *      @tsk with @loginuid.  @buf->mutex must be locked.
90  */
91 static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
92                                unsigned int sessionid,
93                                struct tty_audit_buf *buf)
94 {
95         if (buf->valid == 0)
96                 return;
97         if (audit_enabled == 0)
98                 return;
99         tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor,
100                       buf->data, buf->valid);
101         buf->valid = 0;
102 }
103
104 /**
105  *      tty_audit_buf_push_current      -       Push buffered data out
106  *
107  *      Generate an audit message from the contents of @buf, which is owned by
108  *      the current task.  @buf->mutex must be locked.
109  */
110 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
111 {
112         uid_t auid = audit_get_loginuid(current);
113         unsigned int sessionid = audit_get_sessionid(current);
114         tty_audit_buf_push(current, auid, sessionid, buf);
115 }
116
117 /**
118  *      tty_audit_exit  -       Handle a task exit
119  *
120  *      Make sure all buffered data is written out and deallocate the buffer.
121  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
122  */
123 void tty_audit_exit(void)
124 {
125         struct tty_audit_buf *buf;
126
127         spin_lock_irq(&current->sighand->siglock);
128         buf = current->signal->tty_audit_buf;
129         current->signal->tty_audit_buf = NULL;
130         spin_unlock_irq(&current->sighand->siglock);
131         if (!buf)
132                 return;
133
134         mutex_lock(&buf->mutex);
135         tty_audit_buf_push_current(buf);
136         mutex_unlock(&buf->mutex);
137
138         tty_audit_buf_put(buf);
139 }
140
141 /**
142  *      tty_audit_fork  -       Copy TTY audit state for a new task
143  *
144  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
145  */
146 void tty_audit_fork(struct signal_struct *sig)
147 {
148         spin_lock_irq(&current->sighand->siglock);
149         sig->audit_tty = current->signal->audit_tty;
150         spin_unlock_irq(&current->sighand->siglock);
151 }
152
153 /**
154  *      tty_audit_tiocsti       -       Log TIOCSTI
155  */
156 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
157 {
158         struct tty_audit_buf *buf;
159         int major, minor, should_audit;
160
161         spin_lock_irq(&current->sighand->siglock);
162         should_audit = current->signal->audit_tty;
163         buf = current->signal->tty_audit_buf;
164         if (buf)
165                 atomic_inc(&buf->count);
166         spin_unlock_irq(&current->sighand->siglock);
167
168         major = tty->driver->major;
169         minor = tty->driver->minor_start + tty->index;
170         if (buf) {
171                 mutex_lock(&buf->mutex);
172                 if (buf->major == major && buf->minor == minor)
173                         tty_audit_buf_push_current(buf);
174                 mutex_unlock(&buf->mutex);
175                 tty_audit_buf_put(buf);
176         }
177
178         if (should_audit && audit_enabled) {
179                 uid_t auid;
180                 unsigned int sessionid;
181
182                 auid = audit_get_loginuid(current);
183                 sessionid = audit_get_sessionid(current);
184                 tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
185                               minor, &ch, 1);
186         }
187 }
188
189 /**
190  *      tty_audit_push_task     -       Flush task's pending audit data
191  */
192 void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
193 {
194         struct tty_audit_buf *buf;
195
196         spin_lock_irq(&tsk->sighand->siglock);
197         buf = tsk->signal->tty_audit_buf;
198         if (buf)
199                 atomic_inc(&buf->count);
200         spin_unlock_irq(&tsk->sighand->siglock);
201         if (!buf)
202                 return;
203
204         mutex_lock(&buf->mutex);
205         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
206         mutex_unlock(&buf->mutex);
207
208         tty_audit_buf_put(buf);
209 }
210
211 /**
212  *      tty_audit_buf_get       -       Get an audit buffer.
213  *
214  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
215  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
216  *      reference to the buffer.
217  */
218 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
219 {
220         struct tty_audit_buf *buf, *buf2;
221
222         buf = NULL;
223         buf2 = NULL;
224         spin_lock_irq(&current->sighand->siglock);
225         if (likely(!current->signal->audit_tty))
226                 goto out;
227         buf = current->signal->tty_audit_buf;
228         if (buf) {
229                 atomic_inc(&buf->count);
230                 goto out;
231         }
232         spin_unlock_irq(&current->sighand->siglock);
233
234         buf2 = tty_audit_buf_alloc(tty->driver->major,
235                                    tty->driver->minor_start + tty->index,
236                                    tty->icanon);
237         if (buf2 == NULL) {
238                 audit_log_lost("out of memory in TTY auditing");
239                 return NULL;
240         }
241
242         spin_lock_irq(&current->sighand->siglock);
243         if (!current->signal->audit_tty)
244                 goto out;
245         buf = current->signal->tty_audit_buf;
246         if (!buf) {
247                 current->signal->tty_audit_buf = buf2;
248                 buf = buf2;
249                 buf2 = NULL;
250         }
251         atomic_inc(&buf->count);
252         /* Fall through */
253  out:
254         spin_unlock_irq(&current->sighand->siglock);
255         if (buf2)
256                 tty_audit_buf_free(buf2);
257         return buf;
258 }
259
260 /**
261  *      tty_audit_add_data      -       Add data for TTY auditing.
262  *
263  *      Audit @data of @size from @tty, if necessary.
264  */
265 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
266                         size_t size)
267 {
268         struct tty_audit_buf *buf;
269         int major, minor;
270
271         if (unlikely(size == 0))
272                 return;
273
274         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
275             && tty->driver->subtype == PTY_TYPE_MASTER)
276                 return;
277
278         buf = tty_audit_buf_get(tty);
279         if (!buf)
280                 return;
281
282         mutex_lock(&buf->mutex);
283         major = tty->driver->major;
284         minor = tty->driver->minor_start + tty->index;
285         if (buf->major != major || buf->minor != minor
286             || buf->icanon != tty->icanon) {
287                 tty_audit_buf_push_current(buf);
288                 buf->major = major;
289                 buf->minor = minor;
290                 buf->icanon = tty->icanon;
291         }
292         do {
293                 size_t run;
294
295                 run = N_TTY_BUF_SIZE - buf->valid;
296                 if (run > size)
297                         run = size;
298                 memcpy(buf->data + buf->valid, data, run);
299                 buf->valid += run;
300                 data += run;
301                 size -= run;
302                 if (buf->valid == N_TTY_BUF_SIZE)
303                         tty_audit_buf_push_current(buf);
304         } while (size != 0);
305         mutex_unlock(&buf->mutex);
306         tty_audit_buf_put(buf);
307 }
308
309 /**
310  *      tty_audit_push  -       Push buffered data out
311  *
312  *      Make sure no audit data is pending for @tty on the current process.
313  */
314 void tty_audit_push(struct tty_struct *tty)
315 {
316         struct tty_audit_buf *buf;
317
318         spin_lock_irq(&current->sighand->siglock);
319         if (likely(!current->signal->audit_tty)) {
320                 spin_unlock_irq(&current->sighand->siglock);
321                 return;
322         }
323         buf = current->signal->tty_audit_buf;
324         if (buf)
325                 atomic_inc(&buf->count);
326         spin_unlock_irq(&current->sighand->siglock);
327
328         if (buf) {
329                 int major, minor;
330
331                 major = tty->driver->major;
332                 minor = tty->driver->minor_start + tty->index;
333                 mutex_lock(&buf->mutex);
334                 if (buf->major == major && buf->minor == minor)
335                         tty_audit_buf_push_current(buf);
336                 mutex_unlock(&buf->mutex);
337                 tty_audit_buf_put(buf);
338         }
339 }