• Peter Zijlstra's avatar
    [PATCH] tty: ->signal->tty locking · 24ec839c
    Peter Zijlstra authored
    
    
    Fix the locking of signal->tty.
    
    Use ->sighand->siglock to protect ->signal->tty; this lock is already used
    by most other members of ->signal/->sighand.  And unless we are 'current'
    or the tasklist_lock is held we need ->siglock to access ->signal anyway.
    
    (NOTE: sys_unshare() is broken wrt ->sighand locking rules)
    
    Note that tty_mutex is held over tty destruction, so while holding
    tty_mutex any tty pointer remains valid.  Otherwise the lifetime of ttys
    are governed by their open file handles.  This leaves some holes for tty
    access from signal->tty (or any other non file related tty access).
    
    It solves the tty SLAB scribbles we were seeing.
    
    (NOTE: the change from group_send_sig_info to __group_send_sig_info needs to
           be examined by someone familiar with the security framework, I think
           it is safe given the SEND_SIG_PRIV from other __group_send_sig_info
           invocations)
    
    [schwidefsky@de.ibm.com: 3270 fix]
    [akpm@osdl.org: various post-viro fixes]
    Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
    Acked-by: default avatarAlan Cox <alan@redhat.com>
    Cc: Oleg Nesterov <oleg@tv-sign.ru>
    Cc: Prarit Bhargava <prarit@redhat.com>
    Cc: Chris Wright <chrisw@sous-sol.org>
    Cc: Roland McGrath <roland@redhat.com>
    Cc: Stephen Smalley <sds@tycho.nsa.gov>
    Cc: James Morris <jmorris@namei.org>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Jeff Dike <jdike@addtoit.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Jan Kara <jack@ucw.cz>
    Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    24ec839c