linux-kernel - Re: [PATCH] select: fix sys_select to not leak ERESTARTNOHAND to userspace

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Date:	Mon, 22 Jan 2007 14:59:56 +0100
From:	Paolo Ornati <ornati@...twebnet.it>
To:	Neil Horman <nhorman@...driver.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...l.com, torvalds@...l.com,
	nhorman@...driver.com
Subject: Re: [PATCH] select: fix sys_select to not leak ERESTARTNOHAND to
 userspace

On Tue, 16 Jan 2007 15:13:32 -0500
Neil Horman <nhorman@...driver.com> wrote:

> As it is currently written, sys_select checks its return code to convert
> ERESTARTNOHAND to EINTR.  However, the check is within an if (tvp) clause, and
> so if select is called from userspace with a NULL timeval, then it is possible
> for the ERESTARTNOHAND errno to leak into userspace, which is incorrect.  This
> patch moves that check outside of the conditional, and prevents the errno leak.

the ERESTARTNOHAND thing is handled in arch specific signal code,
syscalls can return -ERESTARTNOHAND as much as they want (and your
change breaks the current behaviour of select()).

For example:

arch/x86_64/kernel/signal.c

        /* Are we from a system call? */
        if ((long)regs->orig_rax >= 0) {
                /* If so, check system call restarting.. */
                switch (regs->rax) {
                        case -ERESTART_RESTARTBLOCK:
                        case -ERESTARTNOHAND:
                                regs->rax = -EINTR;
                                break;

-- 
	Paolo Ornati
	Linux 2.6.20-rc5 on x86_64
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