From: Al Viro <viro@zeniv.linux.org.uk>
To: Christoph Hellwig <hch@lst.de>
Cc: x86@kernel.org, Jan Kara <jack@suse.com>,
linux-arm-kernel@lists.infradead.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH 4/4] quota: simplify the quotactl compat handling
Date: Sun, 26 Jul 2020 17:37:11 +0100 [thread overview]
Message-ID: <20200726163711.GU2786714@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200726163422.GA24657@lst.de>
On Sun, Jul 26, 2020 at 06:34:22PM +0200, Christoph Hellwig wrote:
> On Sun, Jul 26, 2020 at 05:32:14PM +0100, Al Viro wrote:
> > > +static int compat_copy_fs_qfilestat(struct compat_fs_qfilestat __user *to,
> > > + struct fs_qfilestat *from)
> > > +{
> > > + if (copy_to_user(to, from, sizeof(*to)) ||
> > > + put_user(from->qfs_nextents, &to->qfs_nextents))
> > > + return -EFAULT;
> > > + return 0;
> > > +}
> >
> > do we have any need of that put_user()? Note that you don't even call
> > that thing unless compat_need_64bit_alignment_fixup() is true. And AFAICS
> > all such cases are little-endian...
>
> The main reason it is there is to preserve the previous semantics.
> And no, I don't think we actually need it on x86. But what if some
> poor souls adds a BE version that needs this? E.g. arm oabi has similar
> weird alignment, and now imagine someone adding arm64 compat code for
> that..
I'd probably add /* just in case some poor sod fucks up the same way for big-endian biarch */
next to that put_user(), then ;-)
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
To: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Cc: x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
Jan Kara <jack-IBi9RG/b67k@public.gmane.org>,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 4/4] quota: simplify the quotactl compat handling
Date: Sun, 26 Jul 2020 17:37:11 +0100 [thread overview]
Message-ID: <20200726163711.GU2786714@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200726163422.GA24657-jcswGhMUV9g@public.gmane.org>
On Sun, Jul 26, 2020 at 06:34:22PM +0200, Christoph Hellwig wrote:
> On Sun, Jul 26, 2020 at 05:32:14PM +0100, Al Viro wrote:
> > > +static int compat_copy_fs_qfilestat(struct compat_fs_qfilestat __user *to,
> > > + struct fs_qfilestat *from)
> > > +{
> > > + if (copy_to_user(to, from, sizeof(*to)) ||
> > > + put_user(from->qfs_nextents, &to->qfs_nextents))
> > > + return -EFAULT;
> > > + return 0;
> > > +}
> >
> > do we have any need of that put_user()? Note that you don't even call
> > that thing unless compat_need_64bit_alignment_fixup() is true. And AFAICS
> > all such cases are little-endian...
>
> The main reason it is there is to preserve the previous semantics.
> And no, I don't think we actually need it on x86. But what if some
> poor souls adds a BE version that needs this? E.g. arm oabi has similar
> weird alignment, and now imagine someone adding arm64 compat code for
> that..
I'd probably add /* just in case some poor sod fucks up the same way for big-endian biarch */
next to that put_user(), then ;-)
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@zeniv.linux.org.uk>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
x86@kernel.org, linux-kernel@vger.kernel.org,
Jan Kara <jack@suse.com>,
linux-fsdevel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 4/4] quota: simplify the quotactl compat handling
Date: Sun, 26 Jul 2020 17:37:11 +0100 [thread overview]
Message-ID: <20200726163711.GU2786714@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200726163422.GA24657@lst.de>
On Sun, Jul 26, 2020 at 06:34:22PM +0200, Christoph Hellwig wrote:
> On Sun, Jul 26, 2020 at 05:32:14PM +0100, Al Viro wrote:
> > > +static int compat_copy_fs_qfilestat(struct compat_fs_qfilestat __user *to,
> > > + struct fs_qfilestat *from)
> > > +{
> > > + if (copy_to_user(to, from, sizeof(*to)) ||
> > > + put_user(from->qfs_nextents, &to->qfs_nextents))
> > > + return -EFAULT;
> > > + return 0;
> > > +}
> >
> > do we have any need of that put_user()? Note that you don't even call
> > that thing unless compat_need_64bit_alignment_fixup() is true. And AFAICS
> > all such cases are little-endian...
>
> The main reason it is there is to preserve the previous semantics.
> And no, I don't think we actually need it on x86. But what if some
> poor souls adds a BE version that needs this? E.g. arm oabi has similar
> weird alignment, and now imagine someone adding arm64 compat code for
> that..
I'd probably add /* just in case some poor sod fucks up the same way for big-endian biarch */
next to that put_user(), then ;-)
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next prev parent reply other threads:[~2020-07-26 16:37 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-26 16:03 improve compat handling for the i386 u64 alignment quirk Christoph Hellwig
2020-07-26 16:03 ` Christoph Hellwig
2020-07-26 16:03 ` [PATCH 1/4] arm64: stop using <asm/compat.h> directly Christoph Hellwig
2020-07-26 16:03 ` Christoph Hellwig
2020-07-30 17:34 ` Nathan Chancellor
2020-07-30 17:34 ` Nathan Chancellor
2020-07-31 8:41 ` Naresh Kamboju
2020-07-31 8:41 ` Naresh Kamboju
2020-07-26 16:03 ` [PATCH 2/4] compat: lift compat_s64 and compat_u64 to <linux/compat.h> Christoph Hellwig
2020-07-26 16:03 ` Christoph Hellwig
2020-07-29 6:08 ` [PATCH 2/4 v2] " Christoph Hellwig
2020-07-29 6:08 ` Christoph Hellwig
2020-07-26 16:04 ` [PATCH 3/4] compat: add a compat_need_64bit_alignment_fixup() helper Christoph Hellwig
2020-07-26 16:04 ` Christoph Hellwig
2020-07-26 16:04 ` [PATCH 4/4] quota: simplify the quotactl compat handling Christoph Hellwig
2020-07-26 16:04 ` Christoph Hellwig
2020-07-26 16:04 ` Christoph Hellwig
2020-07-26 16:32 ` Al Viro
2020-07-26 16:32 ` Al Viro
2020-07-26 16:34 ` Christoph Hellwig
2020-07-26 16:34 ` Christoph Hellwig
2020-07-26 16:37 ` Al Viro [this message]
2020-07-26 16:37 ` Al Viro
2020-07-26 16:37 ` Al Viro
2020-07-27 12:41 ` Jan Kara
2020-07-27 12:41 ` Jan Kara
2020-07-27 12:41 ` Jan Kara
2020-07-27 15:56 ` Al Viro
2020-07-27 15:56 ` Al Viro
2020-07-27 21:31 ` Jan Kara
2020-07-27 21:31 ` Jan Kara
2020-07-28 1:49 ` Al Viro
2020-07-28 1:49 ` Al Viro
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