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Date: Mon, 26 Sep 2022 10:22:41 +0200 From: Vlastimil Babka <vbabka@...e.cz> To: Chao Yu <chao@...nel.org>, Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins <hugh@...itas.com> Cc: Chao Yu <chao.yu@...o.com>, Christophe JAILLET <christophe.jaillet@...adoo.fr>, Hyeonggon Yoo <42.hyeyoo@...il.com>, Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] mm/slub: clean up create_unique_id() On 9/25/22 09:12, Chao Yu wrote: > From: Chao Yu <chao.yu@...o.com> > > As Christophe JAILLET suggested: > > In create_unique_id(), > > "looks that ID_STR_LENGTH could even be reduced to 32 or 16. > > The 2nd BUG_ON at the end of the function could certainly be just > removed as well or remplaced by a: > if (p > name + ID_STR_LENGTH - 1) { > kfree(name); > return -E<something>; > } > " > > According to above suggestion, let's do below cleanups: > 1. reduce ID_STR_LENGTH to 32, as the buffer size should be enough; > 2. use WARN_ON instead of BUG_ON() and return error if check condition > is true; > 3. use snprintf instead of sprintf to avoid overflow. > > Link: https://lore.kernel.org/linux-mm/2025305d-16db-abdf-6cd3-1fb93371c2b4@wanadoo.fr/ > Fixes: 81819f0fc828 ("SLUB core") > Suggested-by: Christophe JAILLET <christophe.jaillet@...adoo.fr> > Reviewed-by: Hyeonggon Yoo <42.hyeyoo@...il.com> > Signed-off-by: Chao Yu <chao.yu@...o.com> > --- > v2: > - add WARN_ON() instead of return error silently; > - use snprintf instead of sprintf to avoid overflow. > mm/slub.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 4b98dff9be8e..3d37a8a7b965 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -5890,7 +5890,7 @@ static inline struct kset *cache_kset(struct kmem_cache *s) > return slab_kset; > } > > -#define ID_STR_LENGTH 64 > +#define ID_STR_LENGTH 32 > > /* Create a unique string id for a slab cache: > * > @@ -5924,9 +5924,13 @@ static char *create_unique_id(struct kmem_cache *s) > *p++ = 'A'; > if (p != name + 1) > *p++ = '-'; > - p += sprintf(p, "%07u", s->size); > + p += snprintf(p, ID_STR_LENGTH - 1 - (p - name), "%07u", s->size); I think we don't need "- 1" here as snprintf() says: @size: The size of the buffer, including the trailing null space > > - BUG_ON(p > name + ID_STR_LENGTH - 1); > + if (p > name + ID_STR_LENGTH - 1) { > + WARN_ON(1); This would be shorter: if (WARN_ON(p > name...)) > + kfree(name); > + return ERR_PTR(-EINVAL); > + } > return name; > } >
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