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| author | Jan Lübbe <jluebbe@lasnet.de> | 2007-09-29 18:47:51 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-09-29 10:00:15 -0700 |
| commit | a64314e62d89562b6fc77593648bec3acc35bf61 (patch) | |
| tree | 964aba05c1293c2436088905001595a8209e44d1 /drivers | |
| parent | ed7fdff5d6754f9ef9e47bbf0b171d3d96fb7e41 (diff) | |
| download | linux-a64314e62d89562b6fc77593648bec3acc35bf61.tar.gz linux-a64314e62d89562b6fc77593648bec3acc35bf61.tar.bz2 linux-a64314e62d89562b6fc77593648bec3acc35bf61.zip | |
fix console change race exposed by CFS
The new behaviour of CFS exposes a race which occurs if a switch is
requested when vt_mode.mode is VT_PROCESS.
The process with vc->vt_pid is signaled before vc->vt_newvt is set.
This causes the switch to fail when triggered by the monitoing process
because the target is still -1.
[ If the signal sending fails, the subsequent "reset_vc(vc)" will then
reset vt_newvt to -1, so this works for that case too. - Linus ]
Signed-off-by: Jan Lübbe <jluebbe@lasnet.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/char/vt_ioctl.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c index c6f6f4209739..045e6888d15b 100644 --- a/drivers/char/vt_ioctl.c +++ b/drivers/char/vt_ioctl.c @@ -1208,15 +1208,18 @@ void change_console(struct vc_data *new_vc) /* * Send the signal as privileged - kill_pid() will * tell us if the process has gone or something else - * is awry + * is awry. + * + * We need to set vt_newvt *before* sending the signal or we + * have a race. */ + vc->vt_newvt = new_vc->vc_num; if (kill_pid(vc->vt_pid, vc->vt_mode.relsig, 1) == 0) { /* * It worked. Mark the vt to switch to and * return. The process needs to send us a * VT_RELDISP ioctl to complete the switch. */ - vc->vt_newvt = new_vc->vc_num; return; } |