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Mon, 14 Oct 2024 08:53:32 +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 Ju0iMQzcDGc4ewAAD6G6ig (envelope-from ); Mon, 14 Oct 2024 08:53:32 +0000 Message-ID: Date: Mon, 14 Oct 2024 10:53:32 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 To: Feng Tang 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> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Score: -2.80 X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; TO_DN_EQ_ADDR_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; TAGGED_RCPT(0.00)[]; RCPT_COUNT_TWELVE(0.00)[21]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[google.com,linux-foundation.org,linux.com,kernel.org,lge.com,linux.dev,gmail.com,linuxfoundation.org,arm.com,kvack.org,googlegroups.com,vger.kernel.org]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo] X-Spam-Flag: NO X-Spam-Level: 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? Also the checks below repeat some of the checks of ksize(). 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). > > /* 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); > } > } 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; > } > > I've run it with the reproducer of syzbot, so far the issue hasn't been > reproduced on my local machine. > > Thanks, > Feng > >> >> But either way means rewriting 2 commits. I think it's indeed better to drop >> the series now from -next and submit a v3. >> >> Vlastimil >> >> >> Thanks, >> >> -- Marco >> > >>