linux-kernel - Re: [PATCH 1/2] mm: vmalloc: implement vrealloc()

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Message-ID: <Zp-z2IWwGtIH9O4p@infradead.org>
Date: Tue, 23 Jul 2024 06:44:56 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Uladzislau Rezki <urezki@...il.com>
Cc: Danilo Krummrich <dakr@...nel.org>, cl@...ux.com, penberg@...nel.org,
	rientjes@...gle.com, iamjoonsoo.kim@....com,
	akpm@...ux-foundation.org, vbabka@...e.cz, roman.gushchin@...ux.dev,
	42.hyeyoo@...il.com, hch@...radead.org, kees@...nel.org,
	ojeda@...nel.org, wedsonaf@...il.com, mhocko@...nel.org,
	mpe@...erman.id.au, chandan.babu@...cle.com,
	christian.koenig@....com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: vmalloc: implement vrealloc()

On Tue, Jul 23, 2024 at 01:28:32PM +0200, Uladzislau Rezki wrote:
> Concurrent vfree() will lead to use-after-free. Either add a comment
> that a user is responsible for not using vrealloc()/vfree() on the same
> pointer concurrently or use find_unlink_vmap_area() which might be more
> complex when it comes to design of the vrealloc().

You can never use *free concurrently with *realloc.  I guess it doesn't
hurt to clearly document that, but other than that we should not try
to cater to that use pattern at all.