linux-kernel - Re: [PATCH] mm/slab: make __free(kfree) accept error pointers

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Date: Mon, 29 Apr 2024 09:29:58 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...ux.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
cc: Matthew Wilcox <willy@...radead.org>, 
    Peter Zijlstra <peterz@...radead.org>, Pekka Enberg <penberg@...nel.org>, 
    David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, 
    Andrew Morton <akpm@...ux-foundation.org>, 
    Vlastimil Babka <vbabka@...e.cz>, 
    Roman Gushchin <roman.gushchin@...ux.dev>, 
    Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org, 
    linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org, 
    Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH] mm/slab: make __free(kfree) accept error pointers

On Mon, 29 Apr 2024, Dan Carpenter wrote:

> I've always thought freeing pointers that have not been allocated is
> sloppy so I like that kfree() doesn't allow error pointers.  We always
> catch it before it reaches production and that teaches people better
> habbits.  Personally, I like how free_netdev() only accepts valid
> pointers.

kfree() already checks for NULL and ZERO pointers. We should add these 
checks in *one* location.

Maybe issue a WARN_ONCE() and simply treat it as a NULL pointer if an 
error code is passed?