tty: Fix multiple races when setting the controlling terminal

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Claim a read lock on the tasklist_lock while setting the controlling
terminal for the session leader. This fixes multiple races:
1. task_pgrp() and task_session() cannot be safely dereferenced, such
   as passing to get_pid(), without holding either rcu_read_lock() or
   tasklist_lock
2. setsid() unwisely allows any thread in the thread group to
   make the thread group leader the session leader; this makes the
   unlocked reads of ->signal->leader and signal->tty potentially
   unordered, stale or even have spurious values.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Peter Hurley 2014-10-16 14:59:47 -04:00 • committed by Greg Kroah-Hartman

parent ae28fa7216

commit 2c411c1102

1 changed files with 17 additions and 6 deletions

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drivers/tty/tty_io.c

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