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tty: Reset hupped state on open

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A common security idiom is to hangup the current tty (via vhangup())
after forking but before execing a root shell. This hangs up any
existing opens which other processes may have and ensures subsequent
opens have the necessary permissions to open the root shell tty/pty.

Reset the TTY_HUPPED state after the driver has successfully
returned the opened tty (perform the reset while the tty is locked
to avoid racing with concurrent hangups).

Reported-by: Heorhi Valakhanovich <valahanovich@tut.by>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 3.12
Tested-by: Heorhi Valakhanovich <valahanovich@tut.by>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2013-11-19 08:46:27 -05:00 committed by Greg Kroah-Hartman
parent 3dcf344bef
commit d4855e1fc0
1 changed files with 1 additions and 0 deletions
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drivers/tty/tty_io.c
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@ -2086,6 +2086,7 @@ retry_open:
filp->f_op = &tty_fops;
goto retry_open;
}
clear_bit(TTY_HUPPED, &tty->flags);
tty_unlock(tty);