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authorJiri Slaby <jslaby@suse.cz>2010-11-29 10:16:54 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2010-11-29 14:52:48 -0800
commitacfa747baf73922021a047f2d87a2d866f5dbab5 (patch)
treef47037d4c02341a9e4102eddd7dc6c774e6b439d /include
parente2efafbf139d2bfdfe96f2901f03189fecd172e4 (diff)
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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/tty.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h
index c7ea9bc8897..021bfd2f086 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -367,6 +367,7 @@ 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))