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Tue, 13 Oct 2026 15:40:02 +0000 X-Mizu-Trace-ID: 0335801ba07d6e44 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: zhaogongyi@bytedance.com Cc: catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, dev.jain@arm.com, baolin.wang@linux.alibaba.com, lance.yang@linux.dev, mark.rutland@arm.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] arm64/mm: restrict transparent contpte mappings to valid PTEs Date: Tue, 13 Oct 2026 23:39:53 +0800 Message-ID: <20261013153953.77575-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261013093600.54995-1-zhaogongyi@bytedance.com> References: <20261013093600.54995-1-zhaogongyi@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 731B24000A X-Stat-Signature: agrfa7g4ndxer1xagfxntfandpzibus3 X-HE-Tag: 1791906005-64668 X-HE-Meta: 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 8LN5tEDW 6P7X02gXvkWcCQAZfOaudnMg7OY0Ctv7joix3iwIYk3swcmhp1FiS6y+wL5GKX0FjaPSYgE+Zy5DJzN/r+SqNhjTU4wkJ4aZikbSoWMO253HsO0KnCdUkCFUiw8yYtOttLU7pq/aJC1eeSxKrerVuNxXtDPdMSoXybsVfFnE2/wA6/7Xo6VZJeJRiz5MYbm3l6SkELOkV5mT21XpdQjNsSAM3Vum2KQ4IvSQLRql9e7TVN/tmgZPJFD3/Dqk8MvRtVtGJNvuk94Mwt/Mp3F4YdoXdpxKMMBRBtxPK Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Oct 13, 2026 at 05:36:00PM +0800, Zhao Gongyi wrote: [...] > >Fixes: 4602e5757bcc ("arm64/mm: wire up PTE_CONT for user mappings") >Cc: stable@vger.kernel.org >Signed-off-by: Zhao Gongyi >--- Good catch! Thanks! [...] >diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c >index 0acab179f..851fa2e44 100644 >--- a/arch/arm64/mm/contpte.c >+++ b/arch/arm64/mm/contpte.c >@@ -463,6 +463,13 @@ void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, > if (!mm_is_user(mm)) > return __set_ptes(mm, addr, ptep, pte, nr); > >+ /* >+ * Keep the producer-side invariant documented in pgtable.h true even >+ * if a direct caller passes an invalid descriptor with PTE_CONT set. >+ */ >+ if (!pte_valid(pte)) >+ return __set_ptes(mm, addr, ptep, pte_mknoncont(pte), nr); set_ptes() is the only in-tree caller, and it already clears PTE_CONT before we get here ... no? Why not fold !pte_valid(pte) into the !mm_is_user(mm) check below and return __set_ptes() directly? if (!mm_is_user(mm) || !pte_valid(pte)) return __set_ptes(mm, addr, ptep, pte, nr); If a direct caller does pass a !pte_valid PTE with PTE_CONT set, I'd rather add a VM_WARN_ON() to catch that. Silently clearing the bit would hide a caller bug :) Cheers, Lance >+ > end = addr + (nr << PAGE_SHIFT); > pfn = pte_pfn(pte); > prot = pte_pgprot(pte); >-- >2.39.5 (Apple Git-154) >