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Sun, 18 Oct 2026 01:48:27 -0700 (PDT) Message-ID: <6b17c6a5-5164-402f-8d97-2b25f4f9ae8d@gmail.com> Date: Sun, 18 Oct 2026 10:48:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] kasan: fix runtime shadow page table synchronization To: Muchun Song , Andrew Morton , David Hildenbrand , Andrey Ryabinin Cc: Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Dan Williams , linux-mm@kvack.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, muchun.song@linux.dev References: <20261018043501.3257632-1-songmuchun@bytedance.com> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <20261018043501.3257632-1-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 82ADC100004 X-Rspam-User: X-Stat-Signature: i58uxbm3yfx11ayq58z1cifazxhxyr93 X-HE-Tag: 1792313309-10912 X-HE-Meta: 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 3ZLK6kWT 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/18/26 6:35 AM, Muchun Song wrote: > - if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) { > + if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE && > + pmd_none(*pmd)) { > pmd_populate_kernel(&init_mm, pmd, > lm_alias(kasan_early_shadow_pte)); what if the entry already points at the early shadow table? this walks down into it then, which loongarch does on every boot. [snip] > - zero_pmd_populate(pud, addr, next); > + ret = zero_pmd_populate(pud, addr, next, mask); > + if (ret) > + return ret; isn't this a separate fix? it's not in the changelog. [snip] > if (kasan_pud_table(*p4d)) { > + if (ARCH_PAGE_TABLE_SYNC_MASK & PGTBL_P4D_MODIFIED) > + continue; > + doesn't this leave the range on the zero shadow, which memory onlined there later then keeps? would always allocating a table at the synced level once slab is up avoid that? -- cheers, jose a. p-a