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authorOleg Nesterov <oleg@tv-sign.ru>2006-02-15 22:13:26 +0300
committerLinus Torvalds <torvalds@g5.osdl.org>2006-02-15 10:21:24 -0800
commitdadac81b1b86196fcc48fb87620403c4a7174f06 (patch)
treefc19d44716915e55b237af3fb01a09f5be6d91c3 /include
parent3f17da699431ec48540beabc55c54d4b5e66c8e7 (diff)
[PATCH] fix kill_proc_info() vs fork() theoretical race
copy_process: attach_pid(p, PIDTYPE_PID, p->pid); attach_pid(p, PIDTYPE_TGID, p->tgid); What if kill_proc_info(p->pid) happens in between? copy_process() holds current->sighand.siglock, so we are safe in CLONE_THREAD case, because current->sighand == p->sighand. Otherwise, p->sighand is unlocked, the new process is already visible to the find_task_by_pid(), but have a copy of parent's 'struct pid' in ->pids[PIDTYPE_TGID]. This means that __group_complete_signal() may hang while doing do ... while (next_thread() != p) We can solve this problem if we reverse these 2 attach_pid()s: attach_pid() does wmb() group_send_sig_info() calls spin_lock(), which provides a read barrier. // Yes ? I don't think we can hit this race in practice, but still. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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