linux-kernel - Re: [PATCH] compat: Fix RT signal mask corruption via sigprocmask

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Date:	Wed, 9 May 2012 17:00:16 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jan Kiszka <jan.kiszka@...mens.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-arch@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michael Tokarev <mjt@....msk.ru>,
	Anthony Liguori <aliguori@...ibm.com>,
	Kevin Wolf <kwolf@...hat.com>
Subject: Re: [PATCH] compat: Fix RT signal mask corruption via sigprocmask

On Wed, May 9, 2012 at 3:09 PM, Jan Kiszka <jan.kiszka@...mens.com> wrote:
> compat_sys_sigprocmask reads a smaller signal mask from userspace than
> sigprogmask accepts for setting. So the high word of blocked.sig[0] will
> be cleared, releasing any potentially blocked RT signal.

I see what you're trying to do, but I think your patch is wrong.

It may work for SIG_BLOCK and SIG_SETMASK to use the current blocked
bits in the high bits, but I'm pretty sure it doesn't work at all for
SIG_UNBLOCK.

I suspect that compat_sys_sigprocmask() should simply be rewritten to
*not* use sys_sigprocmask() at all, but simply open-code the three
cases directly. IOW, copy the code from sys_sigprocmask(), and modify
it for an incoming/outgoing compat_old_sigset_t.

Hmm?

                    Linus
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