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Thu, 09 Apr 2026 02:12:11 -0700 (PDT) Sender: Michael Neuling From: Michael Neuling To: =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , "Mike Rapoport (Microsoft)" , "Vishal Moola (Oracle)" , Albert Ou , Aleksa Paunovic , Aleksandar Rikalo , Alexandre Ghiti , Andrew Jones , Andrew Morton , Arnd Bergmann , David Hildenbrand , Djordje Todorovic , Guo Ren , Junhui Liu , Kevin Brodsky , Lorenzo Stoakes , Nam Cao , Oleg Nesterov , Oscar Salvador , Palmer Dabbelt , Paul Walmsley , Qinglin Pan , Raj Vishwanathan4 , linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Cc: Michael Neuling Subject: [PATCH 5/5] riscv: mm: Fix TOCTOU race in remove_pte_mapping Date: Thu, 9 Apr 2026 09:11:43 +0000 Message-ID: <20260409091143.1348853-6-mikey@neuling.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260409091143.1348853-1-mikey@neuling.org> References: <20260409091143.1348853-1-mikey@neuling.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit remove_pte_mapping() reads the PTE via ptep_get() (a READ_ONCE) into a local variable, but then checks pte_present(*ptep) by dereferencing the pointer directly, reading the PTE a second time. If another CPU modifies the PTE between the two reads, pte_present may check a different value than what was captured, and the subsequent pte_page() could derive the wrong page to free. Use the already-captured local pte variable for the pte_present check. Fixes: c75a74f4ba ("riscv: mm: Add memory hotplugging support") Signed-off-by: Michael Neuling Assisted-by: Cursor:claude-4.6-opus-high-thinking --- arch/riscv/mm/init.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 23cc1b81fa..873cc860a1 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -1562,7 +1562,7 @@ static void __meminit remove_pte_mapping(pte_t *pte_base, unsigned long addr, un ptep = pte_base + pte_index(addr); pte = ptep_get(ptep); - if (!pte_present(*ptep)) + if (!pte_present(pte)) continue; pte_clear(&init_mm, addr, ptep); -- 2.43.0