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| author | Michal Januszewski <spock@gentoo.org> | 2007-04-01 23:49:51 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-04-02 10:06:09 -0700 |
| commit | f991519c197534811046e5e47389b6fafcdf1e48 (patch) | |
| tree | a8df0ce3aafc97968a354e736305a3fc807f1dea /drivers/char | |
| parent | 1d64b9cb1dc2a7cd521444e3d908adeccd026356 (diff) | |
| download | linux-f991519c197534811046e5e47389b6fafcdf1e48.tar.gz linux-f991519c197534811046e5e47389b6fafcdf1e48.tar.bz2 linux-f991519c197534811046e5e47389b6fafcdf1e48.zip | |
[PATCH] vt: fix potential race in VT_WAITACTIVE handler
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 <spock@gentoo.org>
Acked-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/vt_ioctl.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c index 1fa2da8f4fbe..c9f2dd620e87 100644 --- a/drivers/char/vt_ioctl.c +++ b/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; |