diff options
| author | Jiri Slaby <jslaby@suse.cz> | 2010-11-29 10:16:54 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-12-09 13:32:42 -0800 |
| commit | 99c0f4e21ead35bcf948bc7aa7c413dc4fb7cba0 (patch) | |
| tree | 4a765880aac7c84d415d36277bc455b56e1b97d0 /include | |
| parent | e4138940ac681ca6350c07a8633a0f5d802999f3 (diff) | |
TTY: open/hangup race fixup
commit acfa747baf73922021a047f2d87a2d866f5dbab5 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/tty.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index 67d64e6efe7a..6f62c3055819 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -365,6 +365,7 @@ struct tty_file_private { #define TTY_HUPPED 18 /* Post driver->hangup() */ #define TTY_FLUSHING 19 /* Flushing to ldisc in progress */ #define TTY_FLUSHPENDING 20 /* Queued buffer flush pending */ +#define TTY_HUPPING 21 /* ->hangup() in progress */ #define TTY_WRITE_FLUSH(tty) tty_write_flush((tty)) |