Merge branch 'upstream-linus' of master.kernel.org:/pub/scm/linux/kernel/git/jgarzik...
[linux-2.6] / 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/file.h>
14 #include <linux/tty.h>
15
16 struct tty_audit_buf {
17         atomic_t count;
18         struct mutex mutex;     /* Protects all data below */
19         int major, minor;       /* The TTY which the data is from */
20         unsigned icanon:1;
21         size_t valid;
22         unsigned char *data;    /* Allocated size N_TTY_BUF_SIZE */
23 };
24
25 static struct tty_audit_buf *tty_audit_buf_alloc(int major, int minor,
26                                                  int icanon)
27 {
28         struct tty_audit_buf *buf;
29
30         buf = kmalloc(sizeof (*buf), GFP_KERNEL);
31         if (!buf)
32                 goto err;
33         if (PAGE_SIZE != N_TTY_BUF_SIZE)
34                 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
35         else
36                 buf->data = (unsigned char *)__get_free_page(GFP_KERNEL);
37         if (!buf->data)
38                 goto err_buf;
39         atomic_set(&buf->count, 1);
40         mutex_init(&buf->mutex);
41         buf->major = major;
42         buf->minor = minor;
43         buf->icanon = icanon;
44         buf->valid = 0;
45         return buf;
46
47 err_buf:
48         kfree(buf);
49 err:
50         return NULL;
51 }
52
53 static void tty_audit_buf_free(struct tty_audit_buf *buf)
54 {
55         WARN_ON(buf->valid != 0);
56         if (PAGE_SIZE != N_TTY_BUF_SIZE)
57                 kfree(buf->data);
58         else
59                 free_page((unsigned long)buf->data);
60         kfree(buf);
61 }
62
63 static void tty_audit_buf_put(struct tty_audit_buf *buf)
64 {
65         if (atomic_dec_and_test(&buf->count))
66                 tty_audit_buf_free(buf);
67 }
68
69 /**
70  *      tty_audit_buf_push      -       Push buffered data out
71  *
72  *      Generate an audit message from the contents of @buf, which is owned by
73  *      @tsk with @loginuid.  @buf->mutex must be locked.
74  */
75 static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
76                                struct tty_audit_buf *buf)
77 {
78         struct audit_buffer *ab;
79
80         if (buf->valid == 0)
81                 return;
82         if (audit_enabled == 0)
83                 return;
84         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
85         if (ab) {
86                 char name[sizeof(tsk->comm)];
87
88                 audit_log_format(ab, "tty pid=%u uid=%u auid=%u major=%d "
89                                  "minor=%d comm=", tsk->pid, tsk->uid,
90                                  loginuid, buf->major, buf->minor);
91                 get_task_comm(name, tsk);
92                 audit_log_untrustedstring(ab, name);
93                 audit_log_format(ab, " data=");
94                 audit_log_n_untrustedstring(ab, buf->valid, buf->data);
95                 audit_log_end(ab);
96         }
97         buf->valid = 0;
98 }
99
100 /**
101  *      tty_audit_buf_push_current      -       Push buffered data out
102  *
103  *      Generate an audit message from the contents of @buf, which is owned by
104  *      the current task.  @buf->mutex must be locked.
105  */
106 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
107 {
108         tty_audit_buf_push(current, audit_get_loginuid(current->audit_context),
109                            buf);
110 }
111
112 /**
113  *      tty_audit_exit  -       Handle a task exit
114  *
115  *      Make sure all buffered data is written out and deallocate the buffer.
116  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
117  */
118 void tty_audit_exit(void)
119 {
120         struct tty_audit_buf *buf;
121
122         spin_lock_irq(&current->sighand->siglock);
123         buf = current->signal->tty_audit_buf;
124         current->signal->tty_audit_buf = NULL;
125         spin_unlock_irq(&current->sighand->siglock);
126         if (!buf)
127                 return;
128
129         mutex_lock(&buf->mutex);
130         tty_audit_buf_push_current(buf);
131         mutex_unlock(&buf->mutex);
132
133         tty_audit_buf_put(buf);
134 }
135
136 /**
137  *      tty_audit_fork  -       Copy TTY audit state for a new task
138  *
139  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
140  */
141 void tty_audit_fork(struct signal_struct *sig)
142 {
143         spin_lock_irq(&current->sighand->siglock);
144         sig->audit_tty = current->signal->audit_tty;
145         spin_unlock_irq(&current->sighand->siglock);
146         sig->tty_audit_buf = NULL;
147 }
148
149 /**
150  *      tty_audit_push_task     -       Flush task's pending audit data
151  */
152 void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid)
153 {
154         struct tty_audit_buf *buf;
155
156         spin_lock_irq(&tsk->sighand->siglock);
157         buf = tsk->signal->tty_audit_buf;
158         if (buf)
159                 atomic_inc(&buf->count);
160         spin_unlock_irq(&tsk->sighand->siglock);
161         if (!buf)
162                 return;
163
164         mutex_lock(&buf->mutex);
165         tty_audit_buf_push(tsk, loginuid, buf);
166         mutex_unlock(&buf->mutex);
167
168         tty_audit_buf_put(buf);
169 }
170
171 /**
172  *      tty_audit_buf_get       -       Get an audit buffer.
173  *
174  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
175  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
176  *      reference to the buffer.
177  */
178 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
179 {
180         struct tty_audit_buf *buf, *buf2;
181
182         buf = NULL;
183         buf2 = NULL;
184         spin_lock_irq(&current->sighand->siglock);
185         if (likely(!current->signal->audit_tty))
186                 goto out;
187         buf = current->signal->tty_audit_buf;
188         if (buf) {
189                 atomic_inc(&buf->count);
190                 goto out;
191         }
192         spin_unlock_irq(&current->sighand->siglock);
193
194         buf2 = tty_audit_buf_alloc(tty->driver->major,
195                                    tty->driver->minor_start + tty->index,
196                                    tty->icanon);
197         if (buf2 == NULL) {
198                 audit_log_lost("out of memory in TTY auditing");
199                 return NULL;
200         }
201
202         spin_lock_irq(&current->sighand->siglock);
203         if (!current->signal->audit_tty)
204                 goto out;
205         buf = current->signal->tty_audit_buf;
206         if (!buf) {
207                 current->signal->tty_audit_buf = buf2;
208                 buf = buf2;
209                 buf2 = NULL;
210         }
211         atomic_inc(&buf->count);
212         /* Fall through */
213  out:
214         spin_unlock_irq(&current->sighand->siglock);
215         if (buf2)
216                 tty_audit_buf_free(buf2);
217         return buf;
218 }
219
220 /**
221  *      tty_audit_add_data      -       Add data for TTY auditing.
222  *
223  *      Audit @data of @size from @tty, if necessary.
224  */
225 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
226                         size_t size)
227 {
228         struct tty_audit_buf *buf;
229         int major, minor;
230
231         if (unlikely(size == 0))
232                 return;
233
234         buf = tty_audit_buf_get(tty);
235         if (!buf)
236                 return;
237
238         mutex_lock(&buf->mutex);
239         major = tty->driver->major;
240         minor = tty->driver->minor_start + tty->index;
241         if (buf->major != major || buf->minor != minor
242             || buf->icanon != tty->icanon) {
243                 tty_audit_buf_push_current(buf);
244                 buf->major = major;
245                 buf->minor = minor;
246                 buf->icanon = tty->icanon;
247         }
248         do {
249                 size_t run;
250
251                 run = N_TTY_BUF_SIZE - buf->valid;
252                 if (run > size)
253                         run = size;
254                 memcpy(buf->data + buf->valid, data, run);
255                 buf->valid += run;
256                 data += run;
257                 size -= run;
258                 if (buf->valid == N_TTY_BUF_SIZE)
259                         tty_audit_buf_push_current(buf);
260         } while (size != 0);
261         mutex_unlock(&buf->mutex);
262         tty_audit_buf_put(buf);
263 }
264
265 /**
266  *      tty_audit_push  -       Push buffered data out
267  *
268  *      Make sure no audit data is pending for @tty on the current process.
269  */
270 void tty_audit_push(struct tty_struct *tty)
271 {
272         struct tty_audit_buf *buf;
273
274         spin_lock_irq(&current->sighand->siglock);
275         if (likely(!current->signal->audit_tty)) {
276                 spin_unlock_irq(&current->sighand->siglock);
277                 return;
278         }
279         buf = current->signal->tty_audit_buf;
280         if (buf)
281                 atomic_inc(&buf->count);
282         spin_unlock_irq(&current->sighand->siglock);
283
284         if (buf) {
285                 int major, minor;
286
287                 major = tty->driver->major;
288                 minor = tty->driver->minor_start + tty->index;
289                 mutex_lock(&buf->mutex);
290                 if (buf->major == major && buf->minor == minor)
291                         tty_audit_buf_push_current(buf);
292                 mutex_unlock(&buf->mutex);
293                 tty_audit_buf_put(buf);
294         }
295 }
296
297 /**
298  *      tty_audit_opening       -       A TTY is being opened.
299  *
300  *      As a special hack, tasks that close all their TTYs and open new ones
301  *      are assumed to be system daemons (e.g. getty) and auditing is
302  *      automatically disabled for them.
303  */
304 void tty_audit_opening(void)
305 {
306         int disable;
307
308         disable = 1;
309         spin_lock_irq(&current->sighand->siglock);
310         if (current->signal->audit_tty == 0)
311                 disable = 0;
312         spin_unlock_irq(&current->sighand->siglock);
313         if (!disable)
314                 return;
315
316         task_lock(current);
317         if (current->files) {
318                 struct fdtable *fdt;
319                 unsigned i;
320
321                 /*
322                  * We don't take a ref to the file, so we must hold ->file_lock
323                  * instead.
324                  */
325                 spin_lock(&current->files->file_lock);
326                 fdt = files_fdtable(current->files);
327                 for (i = 0; i < fdt->max_fds; i++) {
328                         struct file *filp;
329
330                         filp = fcheck_files(current->files, i);
331                         if (filp && is_tty(filp)) {
332                                 disable = 0;
333                                 break;
334                         }
335                 }
336                 spin_unlock(&current->files->file_lock);
337         }
338         task_unlock(current);
339         if (!disable)
340                 return;
341
342         spin_lock_irq(&current->sighand->siglock);
343         current->signal->audit_tty = 0;
344         spin_unlock_irq(&current->sighand->siglock);
345 }