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[81.154.179.160]) by smtp.gmail.com with ESMTPSA id f12-20020a5d58ec000000b00309257ad16csm10267702wrd.29.2023.05.23.01.19.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 May 2023 01:19:30 -0700 (PDT) Date: Tue, 23 May 2023 09:19:30 +0100 From: Lorenzo Stoakes To: David Hildenbrand Cc: Vlastimil Babka , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Kees Cook , linux-mm@kvack.org, linux-hardening@vger.kernel.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/slab: remove HAVE_HARDENED_USERCOPY_ALLOCATOR Message-ID: <4674f97f-5f97-45b7-a4b9-a19ca46b7ce1@lucifer.local> References: <20230523073136.4900-1-vbabka@suse.cz> <310077ed-6f3f-41fe-afcf-36500a9408ec@lucifer.local> <623a87c6-c0d2-799a-c39e-0d14dcdfa6df@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 7E05F1C0003 X-Stat-Signature: 4zhm4fiantsh9jcwbn7mjiqfiqg9f7ay X-HE-Tag: 1684829973-162294 X-HE-Meta: U2FsdGVkX19YDTuJ6g/RkQSuB/yjnfGDE+IDB7zgl2ocq7yLU591ivcbUEfARseXogRq8gi+/Hfcw0L4Kg0AWdLY4MC/wmmQ3seVjCAS6INSt/D4QRpZVdf8bRV9AhRUp6Fbz/OzgWzcyN90LLuqLjwKqYLjm2P/+uPnQpVJzVgB0nqnnWHTmXfn1+IpXSaFOxidNWsRSeXlufTd3CEd5QoUOaUP0+xldIQMDXaeEG9c/NmxNj6sn4AIFJqr3EFCQyb8hJjje9mUxUJEF0gWTwhAhrwRTehrUQXN+HWkniODMnsXkIw1fNfdj1yNHmzsS+GHk2vjqXz3kKk7RPxjSgOBbRZAUUTUcJGWs8/5pWRvvm220y5yGmYn6Uen1/z3/YnrFeZRm1ZezaNg7C/SoMSWnc6EbiKocq/drZycgL4Hy28voVCy33MqsWKP8c7aIDL338Z0Kq8irg7pc1MQ0l7kIRLbbLoi0+KY6dQmdRQWQbcGEaBg/ZKLWvNhQaKo7R8o0rI1WEXK8liTNQsYfmTTuwLkUPm9X2P0ufTri06FHV11SiEB34EpG86dLDo4iSAwDPm5dWTxcEqTkr524A6KVtC2rhH3RfZIaVfbD2R0+LnSFYr2YnHN7xFRt+JGMkp5F4siUP/3vViTlYoAm398nr3TcOwpskFvkILZ/E+kAFnaLr8XMY8gdHJeFJu/Ow6Rl8P5WnesiT0umS+KNfk/fbu4wW0rP/rdwIOUYgWXOs4bLYkMfqRlKabo1uHH36IcUpoVprl/apoTvXFuxVNdub0Oj8eh0nygKGZn3S9a/suyNzaktcwtPnRxYvAhT0wrsl4dST1+9xhCdsF1zhCTnZBbs6/1nkxS8Bbxu3pGcpm//CYVa1TODJPFHwkjlPtQdlXX8wJP3yjF8kIJgkzIUZ79e1I+YPF9wJRjxy1ZkeadUmcBa/y/THFABt1ujE6y9oidlHQa+vZWPfq r1D+8qgo 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, May 23, 2023 at 10:14:24AM +0200, David Hildenbrand wrote: > On 23.05.23 09:56, Lorenzo Stoakes wrote: > > On Tue, May 23, 2023 at 09:46:46AM +0200, Vlastimil Babka wrote: > > > On 5/23/23 09:42, Lorenzo Stoakes wrote: > > > > On Tue, May 23, 2023 at 09:31:36AM +0200, Vlastimil Babka wrote: > > > > > With SLOB removed, both remaining allocators support hardened usercopy, > > > > > so remove the config and associated #ifdef. > > > > > > > > > > Signed-off-by: Vlastimil Babka > > > > > --- > > > > > mm/Kconfig | 2 -- > > > > > mm/slab.h | 9 --------- > > > > > security/Kconfig | 8 -------- > > > > > 3 files changed, 19 deletions(-) > > > > > > > > > > diff --git a/mm/Kconfig b/mm/Kconfig > > > > > index 7672a22647b4..041f0da42f2b 100644 > > > > > --- a/mm/Kconfig > > > > > +++ b/mm/Kconfig > > > > > @@ -221,7 +221,6 @@ choice > > > > > config SLAB > > > > > bool "SLAB" > > > > > depends on !PREEMPT_RT > > > > > - select HAVE_HARDENED_USERCOPY_ALLOCATOR > > > > > help > > > > > The regular slab allocator that is established and known to work > > > > > well in all environments. It organizes cache hot objects in > > > > > @@ -229,7 +228,6 @@ config SLAB > > > > > > > > > > config SLUB > > > > > bool "SLUB (Unqueued Allocator)" > > > > > - select HAVE_HARDENED_USERCOPY_ALLOCATOR > > > > > help > > > > > SLUB is a slab allocator that minimizes cache line usage > > > > > instead of managing queues of cached objects (SLAB approach). > > > > > diff --git a/mm/slab.h b/mm/slab.h > > > > > index f01ac256a8f5..695ef96b4b5b 100644 > > > > > --- a/mm/slab.h > > > > > +++ b/mm/slab.h > > > > > @@ -832,17 +832,8 @@ struct kmem_obj_info { > > > > > void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab); > > > > > #endif > > > > > > > > > > -#ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR > > > > > void __check_heap_object(const void *ptr, unsigned long n, > > > > > const struct slab *slab, bool to_user); > > > > > -#else > > > > > -static inline > > > > > -void __check_heap_object(const void *ptr, unsigned long n, > > > > > - const struct slab *slab, bool to_user) > > > > > -{ > > > > > -} > > > > > -#endif > > > > > > > > Hm, this is still defined in slab.c/slub.c and invoked in usercopy.c, do we > > > > not want the prototype? > > > > > > Well I didn't delete the prototype, just the ifdef/else around, so now it's > > > there unconditionally. > > > > > > > Perhaps replacing with #ifdef > > > > CONFIG_HARDENED_USERCOPY instead? I may be missing something here :) > > > > > > Putting it under that #ifdef would work and match that the implementations > > > of that function are under that same ifdef, but maybe it's unnecessary noise > > > in the header? > > > > > > > Yeah my brain inserted extra '-'s there, sorry! > > > > Given we only define __check_heap_object() in sl[au]b.c if > > CONFIG_HARDENED_USERCOPY wouldn't we need to keep the empty version around > > if !CONFIG_HARDENED_USERCOPY since check_heap_object() appears to be called > > unconditionally? > > > > The file is only compiled with CONFIG_HARDENED_USERCOPY: > > mm/Makefile:obj-$(CONFIG_HARDENED_USERCOPY) += usercopy.o > Yeah ugh at this sort of implicit thing. Anyway it'd be preferable to stick #ifdef CONFIG_HARDENED_USERCOPY around the prototype just so it's abundantly clear this function doesn't exist unless that is set. > > > Reviewed-by: David Hildenbrand > > -- > Thanks, > > David / dhildenb >