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=1794419879; b=sTNkyutjlyY5EBAHiduul7u/rolEh7CM7HLO0uyjVY/c+uLrRoCdMX4Ep8GWjXrdretu 63rfBCb6vonTU/a74VOcqKM1tZfBfkJYRA2URQRZpVnSRlYOrMQqIkgGZrvgOCctVaOqz /LfNdTaYSgDPkyGHuBhL0C7ooTWWtV+XE7O63424S8RR8KpQyFmJqaZPKd5XhyEtewclG p9SyLE77eDmeIWAIdvMaCFJVCGL99+IENN1VBGYkOJpEddlHubMi1/2qagIFUZUHXL5rZ 0yCbGbMO04hNtRWMPV87a9amIx37dWr0JqC05B6eug3nLRQQJmXX7xsvi2fIirnBOIg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794419879; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=7MF9O4y9Y0kOiSZlcJC8i4mUMzwg54noD2A3TS6gAo8=; b=2A3t4myBmfVQfrZD5RxbcC8wvw0gx2VObE/QQ4+WUuYQjUN9VrP4IdF5o6CKivx5N5di HBZ/uWZfMqPGB/tEIvymIzNiy70EXwINJccGuBkyasB9uxlxO+cNMkIZxo6I15im+Ust0 WjSBevpJlVDe1Zg7n06HwrwEIqDquaY1LzkggXvF2QzmGHF7MDwaj8tulg1Wa45OD1WoF lAjWo5qN6iOmtLgxUbgPaFdmU0W+2TgpnGECCjzeHhCTKSrzj2RvAXQg5xZOShIYbHJ0K tZqfe68kq9GP1WC017Wf5RVpVTLUpewx6B0BL1rfh3u0hBq5TbYhXDdjkXg7wmVJaiQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=F+q+DPD4; 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 2A98A60A5BE5 for ; Wed, 11 Nov 2026 17:57:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=F+q+DPD4 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 530D91F00A11; Wed, 11 Nov 2026 17:57:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794419879; bh=7MF9O4y9Y0kOiSZlcJC8i4mUMzwg54noD2A3TS6gAo8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=F+q+DPD4E6ISHDMbYyljbGTZEBH6033Rv0zuEyI4Trzbqbikdb1Wl0ucdrv3fAdj5 FkWuRDAXPtyHMxveXglF0NnpFuevQS3nN+nwAYfkeiqjC50ZIlN7K+94Frme29Zule kF9Fm+BBS9hZ/wpM1Ajaom8xCuZ32xCV/3aSwkUPSQ50ZV7N21GfFvzKQ6CnzY9YxF aYhlpF/p9JbecJ69mX+iysLwO8ECIs6SK3ufdntAISeOIPHVUysdLJtzYl2zZVvZIy HXGe+9PElltUDx78TieL0N7MM6TtcDuvfx5FUassM9h64RrYnWcez56pm1Yz5ZCN0b 2cqkNZYOM0v3g== From: Sasha Levin To: stable@vger.kernel.org Cc: Magnus Lindholm , Ivan Kokshaysky , Matoro Mahri , Michael Cree , Sasha Levin Subject: [PATCH 5.15.y 3/4] alpha: fix user-space corruption during memory compaction Date: Wed, 11 Nov 2026 12:57:53 -0500 Message-ID: <20261111175746.3724675-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261111175746.3724675-1-sashal@kernel.org> References: <20261107060811-failed-5.15-fe221b7b2d3e@kernel.org> <20261111175746.3724675-1-sashal@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Magnus Lindholm [ Upstream commit dd5712f3379cfe760267cdd28ff957d9ab4e51c7 ] Alpha systems can suffer sporadic user-space crashes and heap corruption when memory compaction is enabled. Symptoms include SIGSEGV, glibc allocator failures (e.g. "unaligned tcache chunk"), and compiler internal errors. The failures disappear when compaction is disabled or when using global TLB invalidation. The root cause is insufficient TLB shootdown during page migration. Alpha relies on ASN-based MM context rollover for instruction cache coherency, but this alone is not sufficient to prevent stale data or instruction translations from surviving migration. Fix this by introducing a migration-specific helper that combines: - MM context invalidation (ASN rollover), - immediate per-CPU TLB invalidation (TBI), - synchronous cross-CPU shootdown when required. The helper is used only by migration/compaction paths to avoid changing global TLB semantics. Additionally, update flush_tlb_other(), pte_clear(), to use READ_ONCE()/WRITE_ONCE() for correct SMP memory ordering. This fixes observed crashes on both UP and SMP Alpha systems. Reviewed-by: Ivan Kokshaysky Tested-by: Matoro Mahri Tested-by: Michael Cree Signed-off-by: Magnus Lindholm Link: https://lore.kernel.org/r/20260102173603.18247-2-linmag7@gmail.com Signed-off-by: Magnus Lindholm Stable-dep-of: fe221b7b2d3e ("alpha: do not skip TLB shootdown IPIs for kthread-borrowed mms") Signed-off-by: Sasha Levin --- arch/alpha/include/asm/pgtable.h | 33 ++++++++- arch/alpha/include/asm/tlbflush.h | 4 +- arch/alpha/mm/Makefile | 2 +- arch/alpha/mm/tlbflush.c | 112 ++++++++++++++++++++++++++++++ 4 files changed, 148 insertions(+), 3 deletions(-) create mode 100644 arch/alpha/mm/tlbflush.c diff --git a/arch/alpha/include/asm/pgtable.h b/arch/alpha/include/asm/pgtable.h index 8e3cf3c9f913d..e95fa0ee50c00 100644 --- a/arch/alpha/include/asm/pgtable.h +++ b/arch/alpha/include/asm/pgtable.h @@ -17,6 +17,7 @@ #include /* For TASK_SIZE */ #include #include +#include struct mm_struct; struct vm_area_struct; @@ -227,6 +228,9 @@ extern inline void pud_set(pud_t * pudp, pmd_t * pmdp) { pud_val(*pudp) = _PAGE_TABLE | ((((unsigned long) pmdp) - PAGE_OFFSET) << (32-PAGE_SHIFT)); } +extern void migrate_flush_tlb_page(struct vm_area_struct *vma, + unsigned long addr); + extern inline unsigned long pmd_page_vaddr(pmd_t pmd) { @@ -245,7 +249,7 @@ extern inline int pte_none(pte_t pte) { return !pte_val(pte); } extern inline int pte_present(pte_t pte) { return pte_val(pte) & _PAGE_VALID; } extern inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep) { - pte_val(*ptep) = 0; + WRITE_ONCE(pte_val(*ptep), 0); } extern inline int pmd_none(pmd_t pmd) { return !pmd_val(pmd); } @@ -307,6 +311,33 @@ extern inline pte_t * pte_offset_kernel(pmd_t * dir, unsigned long address) extern pgd_t swapper_pg_dir[1024]; +#ifdef CONFIG_COMPACTION +#define __HAVE_ARCH_PTEP_GET_AND_CLEAR + +static inline pte_t ptep_get_and_clear(struct mm_struct *mm, + unsigned long address, + pte_t *ptep) +{ + pte_t pte = READ_ONCE(*ptep); + + pte_clear(mm, address, ptep); + return pte; +} + +#define __HAVE_ARCH_PTEP_CLEAR_FLUSH + +static inline pte_t ptep_clear_flush(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep) +{ + struct mm_struct *mm = vma->vm_mm; + pte_t pte = ptep_get_and_clear(mm, addr, ptep); + + page_table_check_pte_clear(mm, pte); + migrate_flush_tlb_page(vma, addr); + return pte; +} + +#endif /* * The Alpha doesn't have any external MMU info: the kernel page * tables contain all the necessary information. diff --git a/arch/alpha/include/asm/tlbflush.h b/arch/alpha/include/asm/tlbflush.h index 64ea0f130cd57..d79d225da6c76 100644 --- a/arch/alpha/include/asm/tlbflush.h +++ b/arch/alpha/include/asm/tlbflush.h @@ -91,7 +91,9 @@ flush_tlb_other(struct mm_struct *mm) unsigned long *mmc = &mm->context[smp_processor_id()]; /* Check it's not zero first to avoid cacheline ping pong when possible. */ - if (*mmc) *mmc = 0; + + if (READ_ONCE(*mmc)) + WRITE_ONCE(*mmc, 0); } #ifndef CONFIG_SMP diff --git a/arch/alpha/mm/Makefile b/arch/alpha/mm/Makefile index 101dbd06b4ceb..2d05664058f64 100644 --- a/arch/alpha/mm/Makefile +++ b/arch/alpha/mm/Makefile @@ -3,4 +3,4 @@ # Makefile for the linux alpha-specific parts of the memory manager. # -obj-y := init.o fault.o +obj-y := init.o fault.o tlbflush.o diff --git a/arch/alpha/mm/tlbflush.c b/arch/alpha/mm/tlbflush.c new file mode 100644 index 0000000000000..ccbc317b9a348 --- /dev/null +++ b/arch/alpha/mm/tlbflush.c @@ -0,0 +1,112 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Alpha TLB shootdown helpers + * + * Copyright (C) 2025 Magnus Lindholm + * + * Alpha-specific TLB flush helpers that cannot be expressed purely + * as inline functions. + * + * These helpers provide combined MM context handling (ASN rollover) + * and immediate TLB invalidation for page migration and memory + * compaction paths, where lazy shootdowns are insufficient. + */ + +#include +#include +#include +#include +#include +#include + +#define asn_locked() (cpu_data[smp_processor_id()].asn_lock) + +/* + * Migration/compaction helper: combine mm context (ASN) handling with an + * immediate per-page TLB invalidate and (for exec) an instruction barrier. + * + * This mirrors the SMP combined IPI handler semantics, but runs locally on UP. + */ +#ifndef CONFIG_SMP +void migrate_flush_tlb_page(struct vm_area_struct *vma, + unsigned long addr) +{ + struct mm_struct *mm = vma->vm_mm; + int tbi_type = (vma->vm_flags & VM_EXEC) ? 3 : 2; + + /* + * First do the mm-context side: + * If we're currently running this mm, reload a fresh context ASN. + * Otherwise, mark context invalid. + * + * On UP, this is mostly about matching the SMP semantics and ensuring + * exec/i-cache tagging assumptions hold when compaction migrates pages. + */ + if (mm == current->active_mm) + flush_tlb_current(mm); + else + flush_tlb_other(mm); + + /* + * Then do the immediate translation kill for this VA. + * For exec mappings, order instruction fetch after invalidation. + */ + tbi(tbi_type, addr); +} + +#else +struct tlb_mm_and_addr { + struct mm_struct *mm; + unsigned long addr; + int tbi_type; /* 2 = DTB, 3 = ITB+DTB */ +}; + +static void ipi_flush_mm_and_page(void *x) +{ + struct tlb_mm_and_addr *d = x; + + /* Part 1: mm context side (Alpha uses ASN/context as a key mechanism). */ + if (d->mm == current->active_mm && !asn_locked()) + __load_new_mm_context(d->mm); + else + flush_tlb_other(d->mm); + + /* Part 2: immediate per-VA invalidation on this CPU. */ + tbi(d->tbi_type, d->addr); +} + +void migrate_flush_tlb_page(struct vm_area_struct *vma, unsigned long addr) +{ + struct mm_struct *mm = vma->vm_mm; + struct tlb_mm_and_addr d = { + .mm = mm, + .addr = addr, + .tbi_type = (vma->vm_flags & VM_EXEC) ? 3 : 2, + }; + + /* + * One synchronous rendezvous: every CPU runs ipi_flush_mm_and_page(). + * This is the "combined" version of flush_tlb_mm + per-page invalidate. + */ + preempt_disable(); + on_each_cpu(ipi_flush_mm_and_page, &d, 1); + + /* + * mimic flush_tlb_mm()'s mm_users<=1 optimization. + */ + if (atomic_read(&mm->mm_users) <= 1) { + + int cpu, this_cpu; + this_cpu = smp_processor_id(); + + for (cpu = 0; cpu < NR_CPUS; cpu++) { + if (!cpu_online(cpu) || cpu == this_cpu) + continue; + if (READ_ONCE(mm->context[cpu])) + WRITE_ONCE(mm->context[cpu], 0); + } + } + preempt_enable(); +} + +#endif -- 2.53.0