diff options
author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-02-08 04:19:01 -0800 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-08 09:22:26 -0800 |
commit | ee7c82da830ea860b1f9274f1f0cdf99f206e7c2 (patch) | |
tree | 449477479b25ec73a1c2242723b3fb1c09cd936d /fs/binfmt_misc.c | |
parent | 6405f7f4675884b671bee66678e1c2859bdb0e56 (diff) |
wait_task_stopped: simplify and fix races with SIGCONT/SIGKILL/untrace
wait_task_stopped() has multiple races with SIGCONT/SIGKILL. tasklist_lock
does not pin the child in TASK_TRACED/TASK_STOPPED stated, almost all info
reported (including exit_code) may be wrong.
In fact, the code under write_lock_irq(tasklist_lock) is not safe. The child
may be PTRACE_DETACH'ed at this time by another subthread, in that case it is
possible we are no longer its ->parent.
Change wait_task_stopped() to take ->siglock before inspecting the task. This
guarantees that the child can't resume and (for example) clear its
->exit_code, so we don't need to use xchg(&p->exit_code) and re-check. The
only exception is ptrace_stop() which changes ->state and ->exit_code without
->siglock held during abort. But this can only happen if both the tracer and
the tracee are dying (coredump is in progress), we don't care.
With this patch wait_task_stopped() doesn't move the child to the end of
the ->parent list on success. This optimization could be restored, but
in that case we have to take write_lock(tasklist) and do some nasty
checks.
Also change the do_wait() since we don't return EAGAIN any longer.
[akpm@linux-foundation.org: fix up after Willy renamed everything]
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/binfmt_misc.c')
0 files changed, 0 insertions, 0 deletions