linux/include
Jiri Slaby acfa747baf TTY: open/hangup race fixup
Like in the "TTY: don't allow reopen when ldisc is changing" patch,
this one fixes a TTY WARNING as described in the option 1) there:
1) __tty_hangup from tty_ldisc_hangup to tty_ldisc_enable. During this
section tty_lock is held. However tty_lock is temporarily dropped in
the middle of the function by tty_ldisc_hangup.

The fix is to introduce a new flag which we set during the unlocked
window and check it in tty_reopen too. The flag is TTY_HUPPING and is
cleared after TTY_HUPPED is set.

While at it, remove duplicate TTY_HUPPED set_bit. The one after
calling ops->hangup seems to be more correct. But anyway, we hold
tty_lock, so there should be no difference.

Also document the function it does that kind of crap.

Nicely reproducible with two forked children:
static void do_work(const char *tty)
{
	if (signal(SIGHUP, SIG_IGN) == SIG_ERR) exit(1);
	setsid();
	while (1) {
		int fd = open(tty, O_RDWR|O_NOCTTY);
		if (fd < 0) continue;
		if (ioctl(fd, TIOCSCTTY)) continue;
		if (vhangup()) continue;
		close(fd);
	}
	exit(0);
}

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: <Valdis.Kletnieks@vt.edu>
Reported-by: Kyle McMartin <kyle@mcmartin.ca>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-11-29 14:52:48 -08:00
..
acpi
asm-generic asm-generic/stat.h: support 64-bit file time_t for stat() 2010-11-01 15:31:29 -04:00
crypto
drm drm/ttm: Be consistent on ttm_bo_init() failures 2010-11-10 11:52:19 +10:00
keys
linux TTY: open/hangup race fixup 2010-11-29 14:52:48 -08:00
math-emu
media Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6 2010-10-28 09:35:11 -07:00
mtd
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2010-11-12 17:17:55 -08:00
pcmcia
rdma
rxrpc
scsi Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6 2010-10-31 20:43:12 -04:00
sound
trace ext4: Add new ext4 inode tracepoints 2010-11-08 13:51:33 -05:00
video Merge master.kernel.org:/pub/scm/linux/kernel/git/lethal/genesis-2.6 into devel-stable 2010-10-28 20:14:38 +01:00
xen Merge branch 'stable/xen-pcifront-0.8.2' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen 2010-10-28 17:11:17 -07:00
Kbuild