send_sigqueue() checks PF_EXITING, then locks p->sighand->siglock. This is
unsafe: 'p' can exit in between and set ->sighand = NULL. The race is
theoretical, the window is tiny and irqs are disabled by the caller, so I
don't think we need the fix for -stable tree.
Convert send_sigqueue() to use lock_task_sighand() helper.
Also, delete 'p->flags & PF_EXITING' re-check, it is unneeded and the
comment is wrong.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
547679087b