From: David Laight <david.laight.linux@gmail.com>
To: Ricardo Ribalda <ribalda@chromium.org>
Cc: Dave Hansen <dave.hansen@intel.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
Joel Fernandes <joelagnelf@nvidia.com>,
Josh Triplett <josh@joshtriplett.org>,
Boqun Feng <boqun@kernel.org>,
Uladzislau Rezki <urezki@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Zqiang <qiang.zhang@linux.dev>, Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Dan Carpenter <error27@gmail.com>,
rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] x86/uaccess: Fix casting in put_user
Date: Wed, 26 Aug 2026 10:58:32 +0100 [thread overview]
Message-ID: <20260826105832.7f1a6cc5@pumpkin> (raw)
In-Reply-To: <CANiDSCtP3krujoBo0Ai2xSrA5gkgmG5vNQuNXBDX5kK-kbRA7w@mail.gmail.com>
On Tue, 25 Aug 2026 23:15:02 +0200
Ricardo Ribalda <ribalda@chromium.org> wrote:
> Hi Dave
>
> On Tue, 25 Aug 2026 at 23:06, Dave Hansen <dave.hansen@intel.com> wrote:
> >
> > On 8/25/26 13:02, Ricardo Ribalda wrote:
> > > Recent versions of smatch preserved the address space qualifiers with
> > > typeof()[1].
> > >
> > > This fix has discovered an invalid casting in put_user.
> > >
> > > This patch fixes tens of smatch errors like the following:
> > > drivers/media/usb/uvc/uvc_v4l2.c:1112:13: warning: incorrect type in argument 2 (different address spaces)
> > > drivers/media/usb/uvc/uvc_v4l2.c:1112:13: expected void const *from
> > > drivers/media/usb/uvc/uvc_v4l2.c:1112:13: got unsigned int __user *
> >
> > Could we beef up the changelog here a bit, please?
> >
> > What _is_ the invalid casting?
> >
> > What is the fix?
> >
> > Why does it work?
>
> Something like this would be better? I will send a v2 if there are no
> more comments.
>
>
> Recent versions of smatch preserved the address space qualifiers with
> typeof()[1].
>
> This fix has discovered an invalid casting in put_user.
>
> put_user is using a casting with __typeof__(*(ptr)), which keeps the
> qualifiers (__user), instead it should use the macro TYPEOF_UNQUAL()
> that will use __typeof_unqual__ where the compiler supports it.
> __typeof_unqual__ copies the type but not the qualifiers.
This is a spares 'bug'.
You need to fix it without changing normal compiles.
There are enough put_user() calls that is will slow down compiles.
David
>
>
> This patch fixes tens of smatch errors like the following:
> drivers/media/usb/uvc/uvc_v4l2.c:1112:13: warning: incorrect type in
> argument 2 (different address spaces)
> drivers/media/usb/uvc/uvc_v4l2.c:1112:13: expected void const *from
> drivers/media/usb/uvc/uvc_v4l2.c:1112:13: got unsigned int __user *
>
> [1] https://github.com/error27/smatch/commit/e53027a4e816a772403baafa83c09e4a94c1cb8f
>
>
next prev parent reply other threads:[~2026-08-26 9:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-25 20:02 [PATCH 0/2] Fix warnings with recent smatch Ricardo Ribalda
2026-08-25 20:02 ` [PATCH 1/2] rcu: Fix casting while dereferencing rcu pointers Ricardo Ribalda
2026-08-26 9:55 ` David Laight
2026-08-25 20:02 ` [PATCH 2/2] x86/uaccess: Fix casting in put_user Ricardo Ribalda
2026-08-25 21:06 ` Dave Hansen
2026-08-25 21:15 ` Ricardo Ribalda
2026-08-25 22:38 ` Dave Hansen
2026-08-26 9:58 ` David Laight [this message]
2026-08-26 11:11 ` Ricardo Ribalda
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