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do_wait: fix sys_waitid()-specific behaviour

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do_wait() checks ->wo_info to figure out who is the caller.  If it's not
NULL the caller should be sys_waitid(), in that case do_wait() fixes up
the retval or zeros ->wo_info, depending on retval from underlying
function.

This is bug: user can pass ->wo_info == NULL and sys_waitid() will return
incorrect value.

man 2 waitid says:

	waitid(): returns 0 on success

Test-case:

	int main(void)
	{
		if (fork())
			assert(waitid(P_ALL, 0, NULL, WEXITED) == 0);

		return 0;
	}

Result:

	Assertion `waitid(P_ALL, 0, ((void *)0), 4) == 0' failed.

Move that code to sys_waitid().

User-visible change: sys_waitid() will return 0 on success, either
infop is set or not.

Note, there's another bug in wait_noreap_copyout() which affects
return value of sys_waitid(). It will be fixed in next patch.

Signed-off-by: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vitaly Mayatskikh 2009-09-23 15:56:51 -07:00 committed by Linus Torvalds
parent b6e763f07f
commit dfe16dfa4a
1 changed files with 23 additions and 26 deletions
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49
kernel/exit.c
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@ -1645,32 +1645,6 @@ notask:
end:
__set_current_state(TASK_RUNNING);
remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
if (wo->wo_info) {
struct siginfo __user *infop = wo->wo_info;
if (retval > 0)
retval = 0;
else {
/*
* For a WNOHANG return, clear out all the fields
* we would set so the user can easily tell the
* difference.
*/
if (!retval)
retval = put_user(0, &infop->si_signo);
if (!retval)
retval = put_user(0, &infop->si_errno);
if (!retval)
retval = put_user(0, &infop->si_code);
if (!retval)
retval = put_user(0, &infop->si_pid);
if (!retval)
retval = put_user(0, &infop->si_uid);
if (!retval)
retval = put_user(0, &infop->si_status);
}
}
return retval;
}
@ -1715,6 +1689,29 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
wo.wo_stat = NULL;
wo.wo_rusage = ru;
ret = do_wait(&wo);
if (ret > 0) {
ret = 0;
} else if (infop) {
/*
* For a WNOHANG return, clear out all the fields
* we would set so the user can easily tell the
* difference.
*/
if (!ret)
ret = put_user(0, &infop->si_signo);
if (!ret)
ret = put_user(0, &infop->si_errno);
if (!ret)
ret = put_user(0, &infop->si_code);
if (!ret)
ret = put_user(0, &infop->si_pid);
if (!ret)
ret = put_user(0, &infop->si_uid);
if (!ret)
ret = put_user(0, &infop->si_status);
}
put_pid(pid);
/* avoid REGPARM breakage on x86: */