* [PATCH] Cygwin: pinfo: Additional fix for CTTY behavior.
@ 2022-12-28 8:35 Takashi Yano
2023-01-09 9:25 ` Corinna Vinschen
0 siblings, 1 reply; 6+ messages in thread
From: Takashi Yano @ 2022-12-28 8:35 UTC (permalink / raw)
To: cygwin-patches; +Cc: Takashi Yano
The commit 25c4ad6ea52f did not fix the CTTY behavior enough. For
example, in the following test case, TTY will be associated as
a CTTY on the second open() call even though the TTY is already
CTTY of another session. This patch fixes the issue.
#include <unistd.h>
#include <sys/fcntl.h>
int main()
{
if (fork () == 0) {
char *tty = ttyname(0);
int fd;
setsid();
fd = open(tty, O_RDWR);
close(fd);
fd = open(tty, O_RDWR);
usleep (60000000L);
}
return 0;
}
Fixes: 25c4ad6ea52f ("Cygwin: pinfo: Align CTTY behavior to the
statement of POSIX.")
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
winsup/cygwin/fhandler/termios.cc | 1 -
winsup/cygwin/pinfo.cc | 5 +++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/winsup/cygwin/fhandler/termios.cc b/winsup/cygwin/fhandler/termios.cc
index f94e20ff6..5b92cdd31 100644
--- a/winsup/cygwin/fhandler/termios.cc
+++ b/winsup/cygwin/fhandler/termios.cc
@@ -736,7 +736,6 @@ fhandler_termios::ioctl (int cmd, void *varg)
return -1;
}
- myself->ctty = -1;
if (!myself->set_ctty (this, 0))
{
set_errno (EPERM);
diff --git a/winsup/cygwin/pinfo.cc b/winsup/cygwin/pinfo.cc
index 586a4204d..735b3be8e 100644
--- a/winsup/cygwin/pinfo.cc
+++ b/winsup/cygwin/pinfo.cc
@@ -530,7 +530,7 @@ _pinfo::set_ctty (fhandler_termios *fh, int flags)
debug_printf ("old %s, ctty device number %y, tc.ntty device number %y flags & O_NOCTTY %y", __ctty (), ctty, tc.ntty, flags & O_NOCTTY);
if (fh && (ctty <= 0 || ctty == tc.ntty) && !(flags & O_NOCTTY))
{
- if (tc.getsid () && tc.getsid () != sid)
+ if (tc.getsid () && tc.getsid () != sid && ctty == -2)
; /* Do nothing if another session is associated with the TTY. */
else
{
@@ -576,7 +576,8 @@ _pinfo::set_ctty (fhandler_termios *fh, int flags)
an obvious bug surfaces. */
if (sid == pid && !tc.getsid ())
tc.setsid (sid);
- sid = tc.getsid ();
+ if (ctty > 0)
+ sid = tc.getsid ();
/* See above */
if ((!tc.getpgid () || being_debugged ()) && pgid == pid)
tc.setpgid (pgid);
--
2.39.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Cygwin: pinfo: Additional fix for CTTY behavior.
2022-12-28 8:35 [PATCH] Cygwin: pinfo: Additional fix for CTTY behavior Takashi Yano
@ 2023-01-09 9:25 ` Corinna Vinschen
2023-01-10 9:52 ` Takashi Yano
2023-01-10 13:37 ` Takashi Yano
0 siblings, 2 replies; 6+ messages in thread
From: Corinna Vinschen @ 2023-01-09 9:25 UTC (permalink / raw)
To: cygwin-patches
Hi Takashi,
On Dec 28 17:35, Takashi Yano wrote:
> The commit 25c4ad6ea52f did not fix the CTTY behavior enough. For
> example, in the following test case, TTY will be associated as
> a CTTY on the second open() call even though the TTY is already
> CTTY of another session. This patch fixes the issue.
The patch is ok, thanks.
But while looking into this patch, I realized how confusing the old code
is. An unsuspecting reader will have a really hard time to figure out
what ctty values of -1 or -2 actually mean. The CVS log entry from 2012
isn't enlightening either:
On second thought, in the spirit of keeping things kludgy, set ctty to
-2 here as a special flag ...
Would you mind to introduce speaking symbolic values for them and add
some comments to make them more transparent?
Also, given this was a "kludge" from 10 years ago, is it really still
needed?
As I said, it's confusing :}
Thanks,
Corinna
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Cygwin: pinfo: Additional fix for CTTY behavior.
2023-01-09 9:25 ` Corinna Vinschen
@ 2023-01-10 9:52 ` Takashi Yano
2023-01-10 10:35 ` Corinna Vinschen
2023-01-10 13:37 ` Takashi Yano
1 sibling, 1 reply; 6+ messages in thread
From: Takashi Yano @ 2023-01-10 9:52 UTC (permalink / raw)
To: cygwin-patches
On Mon, 9 Jan 2023 10:25:33 +0100
Corinna Vinschen wrote:
> On Dec 28 17:35, Takashi Yano wrote:
> > The commit 25c4ad6ea52f did not fix the CTTY behavior enough. For
> > example, in the following test case, TTY will be associated as
> > a CTTY on the second open() call even though the TTY is already
> > CTTY of another session. This patch fixes the issue.
>
> The patch is ok, thanks.
>
> But while looking into this patch, I realized how confusing the old code
> is. An unsuspecting reader will have a really hard time to figure out
> what ctty values of -1 or -2 actually mean. The CVS log entry from 2012
> isn't enlightening either:
>
> On second thought, in the spirit of keeping things kludgy, set ctty to
> -2 here as a special flag ...
>
> Would you mind to introduce speaking symbolic values for them and add
> some comments to make them more transparent?
Ok. Do you mean, first push this CTTY patch, then,
add comment for ctty values -1 and -2 in another patch?
> Also, given this was a "kludge" from 10 years ago, is it really still
> needed?
>
> As I said, it's confusing :}
Currently, the special values mean:
-1: CTTY is not initialized yet. Can associate with the TTY
which is associated with the own session.
-2: CTTY has been released by setsid(). Can associate with
a new TTY as CTTY, but cannot associate with the TTYs
already associated with other sessions.
So, I think the two different values are necessary.
--
Takashi Yano <takashi.yano@nifty.ne.jp>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Cygwin: pinfo: Additional fix for CTTY behavior.
2023-01-10 9:52 ` Takashi Yano
@ 2023-01-10 10:35 ` Corinna Vinschen
0 siblings, 0 replies; 6+ messages in thread
From: Corinna Vinschen @ 2023-01-10 10:35 UTC (permalink / raw)
To: cygwin-patches
On Jan 10 18:52, Takashi Yano wrote:
> On Mon, 9 Jan 2023 10:25:33 +0100
> Corinna Vinschen wrote:
> > On Dec 28 17:35, Takashi Yano wrote:
> > > The commit 25c4ad6ea52f did not fix the CTTY behavior enough. For
> > > example, in the following test case, TTY will be associated as
> > > a CTTY on the second open() call even though the TTY is already
> > > CTTY of another session. This patch fixes the issue.
> >
> > The patch is ok, thanks.
> >
> > But while looking into this patch, I realized how confusing the old code
> > is. An unsuspecting reader will have a really hard time to figure out
> > what ctty values of -1 or -2 actually mean. The CVS log entry from 2012
> > isn't enlightening either:
> >
> > On second thought, in the spirit of keeping things kludgy, set ctty to
> > -2 here as a special flag ...
> >
> > Would you mind to introduce speaking symbolic values for them and add
> > some comments to make them more transparent?
>
> Ok. Do you mean, first push this CTTY patch, then,
> add comment for ctty values -1 and -2 in another patch?
Sure, that would be fine.
>
> > Also, given this was a "kludge" from 10 years ago, is it really still
> > needed?
> >
> > As I said, it's confusing :}
>
> Currently, the special values mean:
> -1: CTTY is not initialized yet. Can associate with the TTY
> which is associated with the own session.
> -2: CTTY has been released by setsid(). Can associate with
> a new TTY as CTTY, but cannot associate with the TTYs
> already associated with other sessions.
>
> So, I think the two different values are necessary.
Ok, good to know.
Thanks,
Corinna
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Cygwin: pinfo: Additional fix for CTTY behavior.
2023-01-09 9:25 ` Corinna Vinschen
2023-01-10 9:52 ` Takashi Yano
@ 2023-01-10 13:37 ` Takashi Yano
2023-01-10 14:35 ` Corinna Vinschen
1 sibling, 1 reply; 6+ messages in thread
From: Takashi Yano @ 2023-01-10 13:37 UTC (permalink / raw)
To: cygwin-patches
On Mon, 9 Jan 2023 10:25:33 +0100
Corinna Vinschen wrote:
> Also, given this was a "kludge" from 10 years ago, is it really still
> needed?
Ah, do you mean the "kludge":
winsup/cygwin/syscalls.cc: 1455:
/* This is a temporary kludge until all utilities can catch up
with a change in behavior that implements linux functionality:
opening a tty should not automatically cause it to become the
controlling tty for the process. */
if (!(flags & O_NOCTTY) && fd > 2 && myself->ctty != -2)
{
flags |= O_NOCTTY;
/* flag that, if opened, this fhandler could later be capable
of being a controlling terminal if /dev/tty is opened. */
opt |= PC_CTTY;
}
and
winsup/cygwin/dtable.cc: 767:
/* This is a temporary kludge until all utilities can catch up with
a change in behavior that implements linux functionality: opening
a tty should not automatically cause it to become the controlling
tty for the process. */
if (newfd > 2)
flags |= O_NOCTTY;
?
These codes might be able to be deleted. I'll check if these
are not needed.
--
Takashi Yano <takashi.yano@nifty.ne.jp>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Cygwin: pinfo: Additional fix for CTTY behavior.
2023-01-10 13:37 ` Takashi Yano
@ 2023-01-10 14:35 ` Corinna Vinschen
0 siblings, 0 replies; 6+ messages in thread
From: Corinna Vinschen @ 2023-01-10 14:35 UTC (permalink / raw)
To: cygwin-patches
On Jan 10 22:37, Takashi Yano wrote:
> On Mon, 9 Jan 2023 10:25:33 +0100
> Corinna Vinschen wrote:
> > Also, given this was a "kludge" from 10 years ago, is it really still
> > needed?
>
> Ah, do you mean the "kludge":
> winsup/cygwin/syscalls.cc: 1455:
> /* This is a temporary kludge until all utilities can catch up
> with a change in behavior that implements linux functionality:
> opening a tty should not automatically cause it to become the
> controlling tty for the process. */
> if (!(flags & O_NOCTTY) && fd > 2 && myself->ctty != -2)
> {
> flags |= O_NOCTTY;
> /* flag that, if opened, this fhandler could later be capable
> of being a controlling terminal if /dev/tty is opened. */
> opt |= PC_CTTY;
> }
>
> and
>
> winsup/cygwin/dtable.cc: 767:
> /* This is a temporary kludge until all utilities can catch up with
> a change in behavior that implements linux functionality: opening
> a tty should not automatically cause it to become the controlling
> tty for the process. */
> if (newfd > 2)
> flags |= O_NOCTTY;
> ?
>
> These codes might be able to be deleted. I'll check if these
> are not needed.
Actually I meant commit c38a2d837303, introducing the -2 value for ctty.
But yeah, the above stuff is also interesting and every opportunity to
get rid of old workarounds is nice.
Corinna
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-01-10 14:35 UTC | newest]
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2022-12-28 8:35 [PATCH] Cygwin: pinfo: Additional fix for CTTY behavior Takashi Yano
2023-01-09 9:25 ` Corinna Vinschen
2023-01-10 9:52 ` Takashi Yano
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