]> git.baikalelectronics.ru Git - kernel.git/commit
cred: remove task_is_dead() from __task_cred() validation
authorOleg Nesterov <oleg@redhat.com>
Thu, 31 May 2012 23:26:16 +0000 (16:26 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 1 Jun 2012 00:49:28 +0000 (17:49 -0700)
commit3ec1844b8d13428381634bbee570b2c920286af7
tree9a1b3aa79ec2e8374944c23cf57a73790a3fc6ce
parent25e0b01a1c9de0952d9128c9e5e78866bfa389ff
cred: remove task_is_dead() from __task_cred() validation

Commit 239a01fbc04f ("CRED: Fix __task_cred()'s lockdep check and banner
comment"):

    add the following validation condition:

        task->exit_state >= 0

    to permit the access if the target task is dead and therefore
    unable to change its own credentials.

OK, but afaics currently this can only help wait_task_zombie() which calls
__task_cred() without rcu lock.

Remove this validation and change wait_task_zombie() to use task_uid()
instead.  This means we do rcu_read_lock() only to shut up the lockdep,
but we already do the same in, say, wait_task_stopped().

task_is_dead() should die, task->exit_state != 0 means that this task has
passed exit_notify(), only do_wait-like code paths should use this.

Unfortunately, we can't kill task_is_dead() right now, it has already
acquired buggy users in drivers/staging.  The fix already exists.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/cred.h
kernel/exit.c