linux-kernel - Re: [RFC PATCH] vfs: Fix might sleep in load_unaligned

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Message-ID: <20251127072057.EbvhUyG4@linutronix.de>
Date: Thu, 27 Nov 2025 08:20:57 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Xie Yuanbin <xieyuanbin1@...wei.com>
Cc: viro@...iv.linux.org.uk, linux@...linux.org.uk, will@...nel.org,
	david.laight@...box.com, rmk+kernel@...linux.org.uk,
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Subject: Re: [RFC PATCH] vfs: Fix might sleep in load_unaligned_zeropad()
 with rcu read lock held

On 2025-11-27 11:03:16 [+0800], Xie Yuanbin wrote:
> On, Wed, 26 Nov 2025 19:26:40 +0000, Al Viro wrote:
> > For quick and dirty variant (on current tree), how about
> > adding
> > 	if (unlikely(addr > TASK_SIZE) && !user_mode(regs))
> > 		goto no_context;
> >
> > right after
> >
> > 	if (!ttbr0_usermode_access_allowed(regs))
> > 		goto no_context;
> >
> > in do_page_fault() there?
> 
> On, Wed, 26 Nov 2025 23:31:00 +0000, Russell King (Oracle) wrote:
> > Now, for 32-bit ARM, I think I am coming to the conclusion that Al's
> > suggestion is probably the easiest solution. However, whether it has
> > side effects, I couldn't say - the 32-bit ARM fault code has been
> > modified by quite a few people in ways I don't yet understand, so I
> > can't be certain at the moment whether it would cause problems.
> 
> I think I've already submitted a very similar patch, to fix another bug:
> On Thu, 16 Oct 2025 20:16:21 +0800, Xie Yuanbin wrote:
> > +#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
> > +	if (unlikely(addr > TASK_SIZE) && user_mode(regs)) {
> > +		fault = 0;
> > +		code = SEGV_MAPERR;
> > +		goto bad_area;
> > +	}
> > +#endif
> Link: https://lore.kernel.org/20250925025744.6807-1-xieyuanbin1@huawei.com
> 
> However, the patch seems to have received no response for a very long
> time.

This all should be covered by the series here
	https://lore.kernel.org/all/20251110145555.2555055-1-bigeasy@linutronix.de/

or do I miss something.

Sebastian