Messages in this thread | | | Date | Mon, 26 Sep 2022 16:24:08 +0800 | Subject | Re: [PATCH v2] mm/slub: clean up create_unique_id() | From | Chao Yu <> |
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On 2022/9/26 16:22, Vlastimil Babka wrote: > On 9/25/22 09:12, Chao Yu wrote: >> From: Chao Yu <chao.yu@oppo.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@wanadoo.fr> >> Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> >> Signed-off-by: Chao Yu <chao.yu@oppo.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
Oops, my bad.
> >> - 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...))
Thanks for the comments, will update soon.
Thanks,
> >> + kfree(name); >> + return ERR_PTR(-EINVAL); >> + } >> return name; >> } >
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