aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorAlan Cox <alan@lxorguk.ukuu.org.uk>2006-09-29 02:00:03 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-29 09:18:12 -0700
commitca9bda00b4aafc42cd3d1b9d32934463e2993b4c (patch)
treedbb7ba5320bb8d1cbf97b3493687cb87932ad5f4
parentae78bf9c4f5fde3c67e2829505f195d7347ce3e4 (diff)
downloadlinaro-lsk-ca9bda00b4aafc42cd3d1b9d32934463e2993b4c.tar.gz
[PATCH] tty locking on resize
The current kernel serializes console resizes but does not serialize the resize against the tty structure updates. This means that while two parallel resizes cannot mess up the console you can get incorrect results reported. Secondly while doing this I added vc_lock_resize() to lock and resize the console. This leaves all knowledge of the console_sem in the vt/console driver and kicks it out of the tty layer, which is good Thirdly while doing this I decided I couldn't stand "disallocate" any longer so I switched it to "deallocate". Signed-off-by: Alan Cox <alan@redhat.com> Cc: Paul Fulghum <paulkf@microgate.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--drivers/char/selection.c2
-rw-r--r--drivers/char/tty_io.c29
-rw-r--r--drivers/char/vt.c12
-rw-r--r--drivers/char/vt_ioctl.c17
-rw-r--r--include/linux/vt_kern.h3
5 files changed, 36 insertions, 27 deletions
diff --git a/drivers/char/selection.c b/drivers/char/selection.c
index 71093a9fc46..74cff839c85 100644
--- a/drivers/char/selection.c
+++ b/drivers/char/selection.c
@@ -33,7 +33,7 @@ extern void poke_blanked_console(void);
/* Variables for selection control. */
/* Use a dynamic buffer, instead of static (Dec 1994) */
-struct vc_data *sel_cons; /* must not be disallocated */
+struct vc_data *sel_cons; /* must not be deallocated */
static volatile int sel_start = -1; /* cleared by clear_selection */
static int sel_end;
static int sel_buffer_lth;
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index eb881cfa53e..2a1e95b0f28 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -2770,12 +2770,11 @@ static int tiocgwinsz(struct tty_struct *tty, struct winsize __user * arg)
* actually has driver level meaning and triggers a VC resize.
*
* Locking:
- * The console_sem is used to ensure we do not try and resize
- * the console twice at once.
- * FIXME: Two racing size sets may leave the console and kernel
- * parameters disagreeing. Is this exploitable ?
- * FIXME: Random values racing a window size get is wrong
- * should lock here against that
+ * Called function use the console_sem is used to ensure we do
+ * not try and resize the console twice at once.
+ * The tty->termios_sem is used to ensure we don't double
+ * resize and get confused. Lock order - tty->termios.sem before
+ * console sem
*/
static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
@@ -2785,17 +2784,17 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
return -EFAULT;
+
+ down(&tty->termios_sem);
if (!memcmp(&tmp_ws, &tty->winsize, sizeof(*arg)))
- return 0;
+ goto done;
+
#ifdef CONFIG_VT
if (tty->driver->type == TTY_DRIVER_TYPE_CONSOLE) {
- int rc;
-
- acquire_console_sem();
- rc = vc_resize(tty->driver_data, tmp_ws.ws_col, tmp_ws.ws_row);
- release_console_sem();
- if (rc)
- return -ENXIO;
+ if (vc_lock_resize(tty->driver_data, tmp_ws.ws_col, tmp_ws.ws_row)) {
+ up(&tty->termios_sem);
+ return -ENXIO;
+ }
}
#endif
if (tty->pgrp > 0)
@@ -2804,6 +2803,8 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
kill_pg(real_tty->pgrp, SIGWINCH, 1);
tty->winsize = tmp_ws;
real_tty->winsize = tmp_ws;
+done:
+ up(&tty->termios_sem);
return 0;
}
diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 0fca83ededf..b49f0337543 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -885,8 +885,17 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
return err;
}
+int vc_lock_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
+{
+ int rc;
+
+ acquire_console_sem();
+ rc = vc_resize(vc, cols, lines);
+ release_console_sem();
+ return rc;
+}
-void vc_disallocate(unsigned int currcons)
+void vc_deallocate(unsigned int currcons)
{
WARN_CONSOLE_UNLOCKED();
@@ -3790,6 +3799,7 @@ EXPORT_SYMBOL(default_blu);
EXPORT_SYMBOL(update_region);
EXPORT_SYMBOL(redraw_screen);
EXPORT_SYMBOL(vc_resize);
+EXPORT_SYMBOL(vc_lock_resize);
EXPORT_SYMBOL(fg_console);
EXPORT_SYMBOL(console_blank_hook);
EXPORT_SYMBOL(console_blanked);
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index a5628a8b662..a53e382cc10 100644
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -96,7 +96,7 @@ do_kdsk_ioctl(int cmd, struct kbentry __user *user_kbe, int perm, struct kbd_str
if (!perm)
return -EPERM;
if (!i && v == K_NOSUCHMAP) {
- /* disallocate map */
+ /* deallocate map */
key_map = key_maps[s];
if (s && key_map) {
key_maps[s] = NULL;
@@ -819,20 +819,20 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
if (arg > MAX_NR_CONSOLES)
return -ENXIO;
if (arg == 0) {
- /* disallocate all unused consoles, but leave 0 */
+ /* deallocate all unused consoles, but leave 0 */
acquire_console_sem();
for (i=1; i<MAX_NR_CONSOLES; i++)
if (! VT_BUSY(i))
- vc_disallocate(i);
+ vc_deallocate(i);
release_console_sem();
} else {
- /* disallocate a single console, if possible */
+ /* deallocate a single console, if possible */
arg--;
if (VT_BUSY(arg))
return -EBUSY;
if (arg) { /* leave 0 */
acquire_console_sem();
- vc_disallocate(arg);
+ vc_deallocate(arg);
release_console_sem();
}
}
@@ -847,11 +847,8 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
if (get_user(ll, &vtsizes->v_rows) ||
get_user(cc, &vtsizes->v_cols))
return -EFAULT;
- for (i = 0; i < MAX_NR_CONSOLES; i++) {
- acquire_console_sem();
- vc_resize(vc_cons[i].d, cc, ll);
- release_console_sem();
- }
+ for (i = 0; i < MAX_NR_CONSOLES; i++)
+ vc_lock_resize(vc_cons[i].d, cc, ll);
return 0;
}
diff --git a/include/linux/vt_kern.h b/include/linux/vt_kern.h
index 918a29763ae..1009d3fe1fc 100644
--- a/include/linux/vt_kern.h
+++ b/include/linux/vt_kern.h
@@ -33,7 +33,8 @@ extern int fg_console, last_console, want_console;
int vc_allocate(unsigned int console);
int vc_cons_allocated(unsigned int console);
int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines);
-void vc_disallocate(unsigned int console);
+int vc_lock_resize(struct vc_data *vc, unsigned int cols, unsigned int lines);
+void vc_deallocate(unsigned int console);
void reset_palette(struct vc_data *vc);
void do_blank_screen(int entering_gfx);
void do_unblank_screen(int leaving_gfx);