linux-kernel - Re: [PATCH] mm: util: update the kerneldoc for kstrdup

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Date:   Mon, 29 Jun 2020 12:21:34 -0700
From:   Joe Perches <joe@...ches.com>
To:     David Hildenbrand <david@...hat.com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH] mm: util: update the kerneldoc for kstrdup_const()

On Mon, 2020-06-29 at 12:54 +0200, David Hildenbrand wrote:
> On 28.06.20 19:37, Joe Perches wrote:
> > On Sun, 2020-06-28 at 17:25 +0200, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > > 
> > > Memory allocated with kstrdup_const() must not be passed to regular
> > > krealloc() as it is not aware of the possibility of the chunk residing
> > > in .rodata. Since there are no potential users of krealloc_const()
> > > at the moment, let's just update the doc to make it explicit.
> > 
> > Another option would be to return NULL if it's
> > used from krealloc with a pointer into rodata
[]
> > diff --git a/mm/slab_common.c b/mm/slab_common.c
[]
> > @@ -1683,6 +1683,9 @@ static __always_inline void *__do_krealloc(const void *p, size_t new_size,
> >   * @new_size: how many bytes of memory are required.
> >   * @flags: the type of memory to allocate.
> >   *
> > + * If the object pointed to is in rodata (likely from kstrdup_const)
> > + * %NULL is returned.
> > + *
[]
> Won't we have similar issues if somebody would do a kfree() instead of a
> kfree_const()? So I think the original patch makes sense.

Which is why I also suggested making kfree work for
more types of memory freeing earlier this month.

https://lore.kernel.org/lkml/573b3fbd5927c643920e1364230c296b23e7584d.camel@perches.com/