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Fix OpenSSH pty regression on close

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OpenSSH expects the (non-blocking) read() of pty master to return
EAGAIN only if it has received all of the slave-side output after
it has received SIGCHLD. This used to work on pre-3.12 kernels.

This fix effectively forces non-blocking read() and poll() to
block for parallel i/o to complete for all ttys. It also unwinds
these changes:

1) f8747d4a46
   tty: Fix pty master read() after slave closes

2) 52bce7f8d4
   pty, n_tty: Simplify input processing on final close

3) 1a48632ffe
   pty: Fix input race when closing

Inspired by analysis and patch from Marc Aurele La France <tsi@tuyoix.net>

Reported-by: Volth <openssh@volth.com>
Reported-by: Marc Aurele La France <tsi@tuyoix.net>
BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=52
BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=2492
Signed-off-by: Brian Bloniarz <brian.bloniarz@gmail.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Brian Bloniarz
2016-03-06 13:16:30 -08:00
committed by Greg Kroah-Hartman
parent d11df61853
commit 0f40fbbcc3
6 changed files with 44 additions and 75 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/tty/n_hdlc.c
View File

@@ -599,7 +599,7 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
add_wait_queue(&tty->read_wait, &wait);
for (;;) {
if (test_bit(TTY_OTHER_DONE, &tty->flags)) {
if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
ret = -EIO;
break;
}
@@ -827,7 +827,7 @@ static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
/* set bits for operations that won't block */
if (n_hdlc->rx_buf_list.head)
mask |= POLLIN | POLLRDNORM; /* readable */
if (test_bit(TTY_OTHER_DONE, &tty->flags))
if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
mask |= POLLHUP;
if (tty_hung_up_p(filp))
mask |= POLLHUP;