From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793212288; b=mQFaeBc78WjrUji1kpuFzWGP2neMyL2Gz9ejIA99YCHUlshMjOTBzDJExYrVRH3AzJjq ilIAkKByF1v0M3YRM+MgYw2UXXXOiy9eM7favZ0igtRVHwv/JfhH0wdmOjTxWoqtb4Tsy eDLtxzSsVuk4BlkopeRNzwFL8jB2sNPIhcChuNMPu6jP75eKTMZwzSzoGuLvThyxQLAFZ zO6OsCQcj9EPtypuCyUlccHe4UiiqO+Oz+idJ5GGa2FxIGOvCj3VMCnfwRAF8cacTmqwd qfTummaN51e+dKx4uqkT1q1Y1u+aJdB+cLBIyebuXQCavfZ1DVMdfR73OeVrF8X4HWQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793212288; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=MNgXIQ8mvW/zChUFJaVuBFc3KImdO1PuPEJHEFisnyI=; b=wlJ21BtuZucKn9L4zYPbki9gRM8/ftv5QgGJQEVa6gft2NAMvJhTyiDvVIvEazc0D8a1 s8OzHAmPWRlWijeZto0jPEjog3krW1dAW89DnbYEBB/lSUTTUQZUKmtooSp7JNWJQfZz0 EhxVf0+tvauFAQUTKCoiFmEBrREaBqXTgPMG7kqHyCnfZhLwgzd11bJzHROyW4jqRQ14a X55UafiTjYBFw+E1rR3TbpIdzmSPDLSDtzF+ucwoPYzInJhVZUQasKVbbhcbPDFAQ2o8h 7FwJ+2kmvDobPn86pvMVLVEDi2GFA41p10WRwuQ8XcQDHIPWRr73dzI0no7TG1HheMw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=XNr0zdCw; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D81E606A31E; Wed, 28 Oct 2026 18:31:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=XNr0zdCw Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7E8291F031E0; Wed, 28 Oct 2026 18:31:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793212288; bh=MNgXIQ8mvW/zChUFJaVuBFc3KImdO1PuPEJHEFisnyI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XNr0zdCw9PVWibihTaPCepbqcMUCA6/QXTA7soNWE/oyFJSmknkTjuEkzsQ0Pml2t qmPdRO/CQI8WR6Nzq8sfdaSw3wCZCu8N8IL/kdcbySLF82Kr5G2tGZdvajyFibi3J4 jlcuZexpHhrpWrrS27O3UwCqOU2KAObqCCvJZcI0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Karl Mehltretter , Will Deacon , Sasha Levin Subject: [PATCH 6.1 0101/1887] arm64: mm: Fix the lockless page-table walk in show_pte() Date: Wed, 28 Oct 2026 17:36:37 +0100 Message-ID: <20261028170501.532672770@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170459.200466217@linuxfoundation.org> References: <20261028170459.200466217@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Karl Mehltretter [ Upstream commit a77644d009dece1104b6fcc6e322b0e4503db0d6 ] show_pte() walks page tables locklessly and can run with interrupts enabled. A concurrent teardown can free a table page while it is being walked. It can also clear a parent entry after show_pte() checked it; the regular pXd_offset() helpers then reread the cleared entry and can derive a bogus lower-level pointer and fault again. Use the lockless offset helpers with the saved parent entries, as gup_fast() does, and pass the saved PMD to pte_offset_map(). For task page tables, arm64 selects MMU_GATHER_RCU_TABLE_FREE. Disable local interrupts around the walk to hold off RCU-deferred table frees and block the tlb_remove_table_sync_one() IPI until the walk is finished. Place the IRQ guard after the header print. This does not make the output a consistent snapshot, but prevents the task page-table walk from dereferencing a released table page or deriving a pointer from a different parent value. Fixes: 1d18c47c735e ("arm64: MMU fault handling and page table management") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Karl Mehltretter Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- arch/arm64/mm/fault.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index c4120bd80a9b4..5bd5e10c49f18 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -145,6 +146,9 @@ static void show_pte(unsigned long addr) pr_alert("%s pgtable: %luk pages, %llu-bit VAs, pgdp=%016lx\n", mm == &init_mm ? "swapper" : "user", PAGE_SIZE / SZ_1K, vabits_actual, mm_to_pgd_phys(mm)); + + guard(irqsave)(); + pgdp = pgd_offset(mm, addr); pgd = READ_ONCE(*pgdp); pr_alert("[%016lx] pgd=%016llx", addr, pgd_val(pgd)); @@ -158,25 +162,25 @@ static void show_pte(unsigned long addr) if (pgd_none(pgd) || pgd_bad(pgd)) break; - p4dp = p4d_offset(pgdp, addr); + p4dp = p4d_offset_lockless(pgdp, pgd, addr); p4d = READ_ONCE(*p4dp); pr_cont(", p4d=%016llx", p4d_val(p4d)); if (p4d_none(p4d) || p4d_bad(p4d)) break; - pudp = pud_offset(p4dp, addr); + pudp = pud_offset_lockless(p4dp, p4d, addr); pud = READ_ONCE(*pudp); pr_cont(", pud=%016llx", pud_val(pud)); if (pud_none(pud) || pud_bad(pud)) break; - pmdp = pmd_offset(pudp, addr); + pmdp = pmd_offset_lockless(pudp, pud, addr); pmd = READ_ONCE(*pmdp); pr_cont(", pmd=%016llx", pmd_val(pmd)); if (pmd_none(pmd) || pmd_bad(pmd)) break; - ptep = pte_offset_map(pmdp, addr); + ptep = pte_offset_map(&pmd, addr); if (!ptep) break; -- 2.53.0