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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 /kernel
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/fork.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 3683ce10f4a..fbea12d7a94 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1173,8 +1173,6 @@ static task_t *copy_process(unsigned long clone_flags,
if (unlikely(p->ptrace & PT_PTRACED))
__ptrace_link(p, current->parent);
- attach_pid(p, PIDTYPE_PID, p->pid);
- attach_pid(p, PIDTYPE_TGID, p->tgid);
if (thread_group_leader(p)) {
p->signal->tty = current->signal->tty;
p->signal->pgrp = process_group(current);
@@ -1184,6 +1182,8 @@ static task_t *copy_process(unsigned long clone_flags,
if (p->pid)
__get_cpu_var(process_counts)++;
}
+ attach_pid(p, PIDTYPE_TGID, p->tgid);
+ attach_pid(p, PIDTYPE_PID, p->pid);
nr_threads++;
total_forks++;