The patch titled
vt: fix potential race in VT_WAITACTIVE handler
has been added to the -mm tree. Its filename is
vt-fix-potential-race-in-vt_waitactive-handler.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: vt: fix potential race in VT_WAITACTIVE handler
From: Michal Januszewski <[EMAIL PROTECTED]>
On a multiprocessor machine the VT_WAITACTIVE ioctl call may return 0 if
fg_console has already been updated in redraw_screen() but the console
switch itself hasn't been completed. Fix this by checking fg_console in
vt_waitactive() with the console sem held.
Signed-off-by: Michal Januszewski <[EMAIL PROTECTED]>
Acked-by: Antonino Daplas <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
drivers/char/vt_ioctl.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff -puN
drivers/char/vt_ioctl.c~vt-fix-potential-race-in-vt_waitactive-handler
drivers/char/vt_ioctl.c
--- a/drivers/char/vt_ioctl.c~vt-fix-potential-race-in-vt_waitactive-handler
+++ a/drivers/char/vt_ioctl.c
@@ -1039,10 +1039,22 @@ int vt_waitactive(int vt)
add_wait_queue(&vt_activate_queue, &wait);
for (;;) {
- set_current_state(TASK_INTERRUPTIBLE);
retval = 0;
- if (vt == fg_console)
+
+ /*
+ * Synchronize with redraw_screen(). By acquiring the console
+ * semaphore we make sure that the console switch is completed
+ * before we return. If we didn't wait for the semaphore, we
+ * could return at a point where fg_console has already been
+ * updated, but the console switch hasn't been completed.
+ */
+ acquire_console_sem();
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (vt == fg_console) {
+ release_console_sem();
break;
+ }
+ release_console_sem();
retval = -EINTR;
if (signal_pending(current))
break;
_
Patches currently in -mm which might be from [EMAIL PROTECTED] are
vt-fix-potential-race-in-vt_waitactive-handler.patch
-
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