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Mon, 14 Oct 2024 13:12:09 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 3oR5HakYDWeOUAAAD6G6ig (envelope-from ); Mon, 14 Oct 2024 13:12:09 +0000 Message-ID: <0e8d49d2-e89b-44df-9dff-29e8f24de105@suse.cz> Date: Mon, 14 Oct 2024 15:12:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/5] mm/slub: Improve data handling of krealloc() when orig_size is enabled Content-Language: en-US To: Feng Tang , Kees Cook Cc: Marco Elver , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Andrey Konovalov , Shuah Khan , David Gow , Danilo Krummrich , Alexander Potapenko , Andrey Ryabinin , Dmitry Vyukov , Vincenzo Frascino , "linux-mm@kvack.org" , "kasan-dev@googlegroups.com" , "linux-kernel@vger.kernel.org" , Eric Dumazet References: <20240911064535.557650-1-feng.tang@intel.com> <49ef066d-d001-411e-8db7-f064bdc2104c@suse.cz> <2382d6e1-7719-4bf9-8a4a-1e2c32ee7c9f@suse.cz> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspam-User: X-Rspamd-Queue-Id: 702161C0004 X-Rspamd-Server: rspam01 X-Stat-Signature: kkhemakgkjjoepdfityy9un9sq8x7dw5 X-HE-Tag: 1728911519-278520 X-HE-Meta: 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 U+x0b8WN dOftUPKzKxKcLPkMicKbHd0ss3n5OiaRmC5y3fNrV9n7hLIuVelRJz0diBVvH9hpSCntG940Pil0EqkhOGku8lh1pyO7D6NhNd7INcCJYjKubT8aZtpdDQPp5mjIti3lEbkbleTnivf5QDluErHV3LjsfxabTGOJDoKKhJRVCo9QIptAEpNRXCB3J5OzsRkKRgzeiJVKLkwu920GTN3RmOikVsyQjR/CqfW1dhAYHUzF5mx+Qb13/NO4EkNPLcHtMRJlqKXTgppnm2O0ntlGolmMAqM8XiXqRUIxIfqanPq6D0virVhp+hK90fZUJq8iCy3Hi2C7kraHH8tGjMLQsWbzHuWWS2LOy0WENcjdSczC5uoCa+5NTO71q/8vAEXwrQ65h6c9PtrAp6DjVk59um15HV2cTIm7UoJcKAzAxkkgj4WTltZwIDZcSCxMN2FUkwXG0 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: List-Subscribe: List-Unsubscribe: On 10/14/24 14:52, Feng Tang wrote: > On Mon, Oct 14, 2024 at 10:53:32AM +0200, Vlastimil Babka wrote: >> On 10/14/24 09:52, Feng Tang wrote: >> > On Fri, Oct 04, 2024 at 05:52:10PM +0800, Vlastimil Babka wrote: >> > Thanks for the suggestion! >> > >> > As there were error report about the NULL slab for big kmalloc object, how >> > about the following code for >> > >> > __do_krealloc(const void *p, size_t new_size, gfp_t flags) >> > { >> > void *ret; >> > size_t ks = 0; >> > int orig_size = 0; >> > struct kmem_cache *s = NULL; >> > >> > /* Check for double-free. */ >> > if (likely(!ZERO_OR_NULL_PTR(p))) { >> > if (!kasan_check_byte(p)) >> > return NULL; >> > >> > ks = ksize(p); >> >> I think this will result in __ksize() doing >> skip_orig_size_check(folio_slab(folio)->slab_cache, object); >> and we don't want that? > > I think that's fine. As later code will re-set the orig_size anyway. But you also read it first. >> > /* Some objects have no orig_size, like big kmalloc case */ >> > if (is_kfence_address(p)) { >> > orig_size = kfence_ksize(p); >> > } else if (virt_to_slab(p)) { >> > s = virt_to_cache(p); >> > orig_size = get_orig_size(s, (void *)p); here. >> > } >> Also the checks below repeat some of the checks of ksize(). > > Yes, there is some redundancy, mostly the virt_to_slab() > >> So I think in __do_krealloc() we should do things manually to determine ks >> and not call ksize(). Just not break any of the cases ksize() handles >> (kfence, large kmalloc). > > OK, originally I tried not to expose internals of __ksize(). Let me > try this way. ksize() makes assumptions that a user outside of slab itself is calling it. But we (well mostly Kees) also introduced kmalloc_size_roundup() to avoid querying ksize() for the purposes of writing beyond the original kmalloc(size) up to the bucket size. So maybe we can also investigate if the skip_orig_size_check() mechanism can be removed now? Still I think __do_krealloc() should rather do its own thing and not call ksize(). > Thanks, > Feng > >> >> > >> > } else { >> > goto alloc_new; >> > } >> > >> > /* If the object doesn't fit, allocate a bigger one */ >> > if (new_size > ks) >> > goto alloc_new; >> > >> > /* Zero out spare memory. */ >> > if (want_init_on_alloc(flags)) { >> > kasan_disable_current(); >> > if (orig_size && orig_size < new_size) >> > memset((void *)p + orig_size, 0, new_size - orig_size); >> > else >> > memset((void *)p + new_size, 0, ks - new_size); >> > kasan_enable_current(); >> > } >> > >> > /* Setup kmalloc redzone when needed */ >> > if (s && slub_debug_orig_size(s) && !is_kfence_address(p)) { >> > set_orig_size(s, (void *)p, new_size); >> > if (s->flags & SLAB_RED_ZONE && new_size < ks) >> > memset_no_sanitize_memory((void *)p + new_size, >> > SLUB_RED_ACTIVE, ks - new_size); >> > } >> > >> > p = kasan_krealloc((void *)p, new_size, flags); >> > return (void *)p; >> > >> > alloc_new: >> > ret = kmalloc_node_track_caller_noprof(new_size, flags, NUMA_NO_NODE, _RET_IP_); >> > if (ret && p) { >> > /* Disable KASAN checks as the object's redzone is accessed. */ >> > kasan_disable_current(); >> > memcpy(ret, kasan_reset_tag(p), orig_size ?: ks); >> > kasan_enable_current(); >> > } >> > >> > return ret; >> > }