linux-kernel - Re: [RFC PATCH v2 1/2] mm/mremap: Fix uprobe anon page be overwritten when expanding vma during mremap

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Message-ID: <20250527151715.GC8333@redhat.com>
Date: Tue, 27 May 2025 17:17:15 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Pu Lehui <pulehui@...weicloud.com>, mhiramat@...nel.org,
	peterz@...radead.org, akpm@...ux-foundation.org,
	Liam.Howlett@...cle.com, vbabka@...e.cz, jannh@...gle.com,
	pfalcato@...e.de, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	pulehui@...wei.com
Subject: Re: [RFC PATCH v2 1/2] mm/mremap: Fix uprobe anon page be
 overwritten when expanding vma during mremap

On 05/27, Lorenzo Stoakes wrote:
>
> I am by the way assuming that uprobes work by installing a special PTE at
> page offset 0 and only in the case where there is something installed here
> do we need to worry.

perhaps I misunderstood you but no...

Basically, we have uprobe_register(struct inode *inode, loff_t offset, ...).
If / when a process mmaps this inode/file and the (new) VMA includes this offset,
we need to call uprobe_mmap() to install the breakpoint at the virtual address
which corresponds to this offset.

Oleg.