linux-kernel - Re: [PATCH v3 2/5] mm/mseal: update madvise() logic

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Message-ID: <ef111032-e108-4771-9202-b8cdab278422@redhat.com>
Date: Thu, 24 Jul 2025 23:41:04 +0200
From: David Hildenbrand <david@...hat.com>
To: Kees Cook <kees@...nel.org>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
 Pedro Falcato <pfalcato@...e.de>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Jeff Xu <jeffxu@...omium.org>
Subject: Re: [PATCH v3 2/5] mm/mseal: update madvise() logic

On 24.07.25 23:32, David Hildenbrand wrote:
>> As an aside, why should discard work in this case even without step 4?
>> Wouldn't setting "read-only" imply you don't want the memory to change
>> out from under you? I guess I'm not clear on the semantics: how do memory
>> protection bits map to madvise actions like this?
> 
> They generally don't affect MADV_DONTNEED behavior. The only documented
> (man page) reason for EPERM in the man page is related to MADV_HWPOISON.
> 

(Exception: MADV_POPULATE_READ/MADV_POPULATE_WRITE requires 
corresponding permissions)

-- 
Cheers,

David / dhildenb