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Commit 41126226e186d92a45ed664e546abb5204588359

Authored by Miloslav Trmac
Committed by Al Viro
1 parent 7719e437fa
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

[patch 1/2] audit: let userspace fully control TTY input auditing 

Remove the code that automatically disables TTY input auditing in processes
that open TTYs when they have no other TTY open; this heuristic was
intended to automatically handle daemons, but it has false positives (e.g.
with sshd) that make it impossible to control TTY input auditing from a PAM
module.  With this patch, TTY input auditing is controlled from user-space
only.

On the other hand, not even for daemons does it make sense to audit "input"
from PTY masters; this data was produced by a program writing to the PTY
slave, and does not represent data entered by the user.

Signed-off-by: Miloslav Trmac <mitr@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Showing 3 changed files with 5 additions and 59 deletions Side-by-side Diff

drivers/char/tty_audit.c
Diff comments   View file @ 4112622
... ... @@ -233,6 +233,10 @@
233 233 if (unlikely(size == 0))
234 234 return;
235 235  
  236 + if (tty->driver->type == TTY_DRIVER_TYPE_PTY
  237 + && tty->driver->subtype == PTY_TYPE_MASTER)
  238 + return;
  239 +
236 240 buf = tty_audit_buf_get(tty);
237 241 if (!buf)
238 242 return;
... ... @@ -294,55 +298,5 @@
294 298 mutex_unlock(&buf->mutex);
295 299 tty_audit_buf_put(buf);
296 300 }
297   -}
298   -
299   -/**
300   - * tty_audit_opening - A TTY is being opened.
301   - *
302   - * As a special hack, tasks that close all their TTYs and open new ones
303   - * are assumed to be system daemons (e.g. getty) and auditing is
304   - * automatically disabled for them.
305   - */
306   -void tty_audit_opening(void)
307   -{
308   - int disable;
309   -
310   - disable = 1;
311   - spin_lock_irq(&current->sighand->siglock);
312   - if (current->signal->audit_tty == 0)
313   - disable = 0;
314   - spin_unlock_irq(&current->sighand->siglock);
315   - if (!disable)
316   - return;
317   -
318   - task_lock(current);
319   - if (current->files) {
320   - struct fdtable *fdt;
321   - unsigned i;
322   -
323   - /*
324   - * We don't take a ref to the file, so we must hold ->file_lock
325   - * instead.
326   - */
327   - spin_lock(&current->files->file_lock);
328   - fdt = files_fdtable(current->files);
329   - for (i = 0; i < fdt->max_fds; i++) {
330   - struct file *filp;
331   -
332   - filp = fcheck_files(current->files, i);
333   - if (filp && is_tty(filp)) {
334   - disable = 0;
335   - break;
336   - }
337   - }
338   - spin_unlock(&current->files->file_lock);
339   - }
340   - task_unlock(current);
341   - if (!disable)
342   - return;
343   -
344   - spin_lock_irq(&current->sighand->siglock);
345   - current->signal->audit_tty = 0;
346   - spin_unlock_irq(&current->sighand->siglock);
347 301 }
drivers/char/tty_io.c
Diff comments   View file @ 4112622
... ... @@ -2755,7 +2755,6 @@
2755 2755 __proc_set_tty(current, tty);
2756 2756 spin_unlock_irq(&current->sighand->siglock);
2757 2757 mutex_unlock(&tty_mutex);
2758   - tty_audit_opening();
2759 2758 return 0;
2760 2759 }
2761 2760  
2762 2761  
... ... @@ -2818,10 +2817,8 @@
2818 2817  
2819 2818 check_tty_count(tty, "tty_open");
2820 2819 retval = ptm_driver->open(tty, filp);
2821   - if (!retval) {
2822   - tty_audit_opening();
  2820 + if (!retval)
2823 2821 return 0;
2824   - }
2825 2822 out1:
2826 2823 release_dev(filp);
2827 2824 return retval;
... ... @@ -300,7 +300,6 @@
300 300 extern void tty_vhangup(struct tty_struct * tty);
301 301 extern void tty_unhangup(struct file *filp);
302 302 extern int tty_hung_up_p(struct file * filp);
303   -extern int is_tty(struct file *filp);
304 303 extern void do_SAK(struct tty_struct *tty);
305 304 extern void __do_SAK(struct tty_struct *tty);
306 305 extern void disassociate_ctty(int priv);
... ... @@ -352,7 +351,6 @@
352 351 extern void tty_audit_fork(struct signal_struct *sig);
353 352 extern void tty_audit_push(struct tty_struct *tty);
354 353 extern void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid);
355   -extern void tty_audit_opening(void);
356 354 #else
357 355 static inline void tty_audit_add_data(struct tty_struct *tty,
358 356 unsigned char *data, size_t size)
... ... @@ -368,9 +366,6 @@
368 366 {
369 367 }
370 368 static inline void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
371   -{
372   -}
373   -static inline void tty_audit_opening(void)
374 369 {
375 370 }
376 371 #endif