linux-kernel - Re: [PATCH] mm: Check writable zero page in page table check

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Message-ID: <467b0cdb4f876b87b50d1cd7229a8e6e02a19a41.camel@intel.com>
Date:   Mon, 5 Sep 2022 18:50:48 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Huang, Shaoqin" <shaoqin.huang@...el.com>,
        "pasha.tatashin@...een.com" <pasha.tatashin@...een.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: Check writable zero page in page table check

On Sat, 2022-09-03 at 10:13 +0800, Huang, Shaoqin wrote:
> > +     BUG_ON(is_zero_pfn(pfn) && rw);
> > +
> 
> Why we need use BUG_ON() here? Based on [1], we should avoid to use
> the 
> BUG_ON() due to it will panic the machine.
> 
> [1]: 
> https://lore.kernel.org/lkml/20220824163100.224449-1-david@redhat.com/

Yea, you are probably right. All the rest of this checker uses BUG_ON()
though. Maybe they should all be something else? Just felt weird to
have this be the only check that is different.

I don't have any objections to changing it to WARN_ON(). Should I
switch the rest of the checks here while I'm at it?