linux-kernel - Re: [PATCH] aio: Fix io_pgetevents() struct __compat_aio

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Message-ID: <20191021201550.GW26530@ZenIV.linux.org.uk>
Date:   Mon, 21 Oct 2019 21:15:50 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Jan Kara <jack@...e.cz>
Cc:     Guillem Jover <guillem@...rons.org>, linux-aio@...ck.org,
        Christoph Hellwig <hch@....de>, Jeff Moyer <jmoyer@...hat.com>,
        Benjamin LaHaise <bcrl@...ck.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] aio: Fix io_pgetevents() struct __compat_aio_sigset
 layout

On Thu, Oct 17, 2019 at 03:48:00PM +0200, Jan Kara wrote:
> On Wed 21-08-19 05:38:20, Guillem Jover wrote:
> > This type is used to pass the sigset_t from userland to the kernel,
> > but it was using the kernel native pointer type for the member
> > representing the compat userland pointer to the userland sigset_t.
> > 
> > This messes up the layout, and makes the kernel eat up both the
> > userland pointer and the size members into the kernel pointer, and
> > then reads garbage into the kernel sigsetsize. Which makes the sigset_t
> > size consistency check fail, and consequently the syscall always
> > returns -EINVAL.
> > 
> > This breaks both libaio and strace on 32-bit userland running on 64-bit
> > kernels. And there are apparently no users in the wild of the current
> > broken layout (at least according to codesearch.debian.org and a brief
> > check over github.com search). So it looks safe to fix this directly
> > in the kernel, instead of either letting userland deal with this
> > permanently with the additional overhead or trying to make the syscall
> > infer what layout userland used, even though this is also being worked
> > around in libaio to temporarily cope with kernels that have not yet
> > been fixed.
> > 
> > We use a proper compat_uptr_t instead of a compat_sigset_t pointer.
> > 
> > Fixes: 7a074e96 ("aio: implement io_pgetevents")
> > Signed-off-by: Guillem Jover <guillem@...rons.org>
> 
> This patch seems to have fallen through the cracks. Al?

Looks like - back then I assumed that Jens would've picked it...
Applied to #fixes...