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SubjectRe: [PATCH] more SAK stuff
>> (a) It does less, namely will not kill processes with uid 0.
>> Ted, any objections?

Alan:

> That breaks the security guarantee. Suppose I use a setuid app to confuse
> you into doing something ?

On second thoughts I agree. Here is the patch without test for p->uid.

Andries

diff -u --recursive --new-file ../linux-2.4.6-pre8/linux/drivers/char/keyboard.c ./linux/drivers/char/keyboard.c
--- ../linux-2.4.6-pre8/linux/drivers/char/keyboard.c Mon Oct 16 21:58:51 2000
+++ ./linux/drivers/char/keyboard.c Mon Jul 2 13:28:09 2001
@@ -506,6 +506,8 @@
* them properly.
*/

+ if (!tty && ttytab && ttytab[0] && ttytab[0]->driver_data)
+ tty = ttytab[0];
do_SAK(tty);
reset_vc(fg_console);
#if 0
diff -u --recursive --new-file ../linux-2.4.6-pre8/linux/drivers/char/tty_io.c ./linux/drivers/char/tty_io.c
--- ../linux-2.4.6-pre8/linux/drivers/char/tty_io.c Sun Jul 1 15:19:26 2001
+++ ./linux/drivers/char/tty_io.c Mon Jul 2 14:53:52 2001
@@ -1818,20 +1818,29 @@
*
* Nasty bug: do_SAK is being called in interrupt context. This can
* deadlock. We punt it up to process context. AKPM - 16Mar2001
+ *
+ * Treat all VTs as a single tty for the purposes of SAK. A process with an
+ * open fd for one VT can do interesting things to all. aeb, 2001-07-02
*/
-static void __do_SAK(void *arg)
+#ifdef CONFIG_VT
+static inline int tty_is_vt(struct tty_struct *tty)
{
-#ifdef TTY_SOFT_SAK
- tty_hangup(tty);
+ return tty ? (tty->driver.type == TTY_DRIVER_TYPE_CONSOLE) : 0;
+}
#else
- struct tty_struct *tty = arg;
+static inline int tty_is_vt(struct tty_struct *tty)
+{
+ return 0;
+}
+#endif
+
+static inline void tty_hard_SAK(struct tty_struct *tty)
+{
struct task_struct *p;
int session;
- int i;
- struct file *filp;
-
- if (!tty)
- return;
+ int i;
+ struct file *filp;
+
session = tty->session;
if (tty->ldisc.flush_buffer)
tty->ldisc.flush_buffer(tty);
@@ -1839,7 +1848,9 @@
tty->driver.flush_buffer(tty);
read_lock(&tasklist_lock);
for_each_task(p) {
+ /* all VTs are considered a single tty here */
if ((p->tty == tty) ||
+ (tty_is_vt(tty) && tty_is_vt(p->tty)) ||
((session > 0) && (p->session == session))) {
send_sig(SIGKILL, p, 1);
continue;
@@ -1850,7 +1861,9 @@
for (i=0; i < p->files->max_fds; i++) {
filp = fcheck_files(p->files, i);
if (filp && (filp->f_op == &tty_fops) &&
- (filp->private_data == tty)) {
+ (filp->private_data == tty ||
+ (tty_is_vt(tty) &&
+ tty_is_vt(filp->private_data)))) {
send_sig(SIGKILL, p, 1);
break;
}
@@ -1860,6 +1873,17 @@
task_unlock(p);
}
read_unlock(&tasklist_lock);
+}
+
+static void __do_SAK(void *arg)
+{
+ struct tty_struct *tty = arg;
+ if (!tty) /* impossible */
+ return;
+#ifdef TTY_SOFT_SAK
+ tty_hangup(tty);
+#else
+ tty_hard_SAK(tty);
#endif
}

@@ -1872,6 +1896,8 @@
*/
void do_SAK(struct tty_struct *tty)
{
+ if (!tty)
+ return;
PREPARE_TQUEUE(&tty->SAK_tq, __do_SAK, tty);
schedule_task(&tty->SAK_tq);
}
-
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