From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f72.google.com (mail-pl0-f72.google.com [209.85.160.72]) by kanga.kvack.org (Postfix) with ESMTP id 7F4546B0033 for ; Thu, 28 Dec 2017 06:33:54 -0500 (EST) Received: by mail-pl0-f72.google.com with SMTP id 31so23327862plk.20 for ; Thu, 28 Dec 2017 03:33:54 -0800 (PST) Received: from huawei.com ([45.249.212.32]) by mx.google.com with ESMTPS id t197si17120326pgc.511.2017.12.28.03.33.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Dec 2017 03:33:53 -0800 (PST) From: Hanjun Guo Subject: [RFC patch] ioremap: don't set up huge I/O mappings when p4d/pud/pmd is zero Date: Thu, 28 Dec 2017 19:24:21 +0800 Message-ID: <1514460261-65222-1-git-send-email-guohanjun@huawei.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: linuxarm@huawei.com, linux-mm@kvack.org, Hanjun Guo , Toshi Kani , Mark Rutland , Will Deacon , Catalin Marinas , Michal Hocko , Andrew Morton , Xuefeng Wang From: Hanjun Guo When we using iounmap() to free the 4K mapping, it just clear the PTEs but leave P4D/PUD/PMD unchanged, also will not free the memory of page tables. This will cause issues on ARM64 platform (not sure if other archs have the same issue) for this case: 1. ioremap a 4K size, valid page table will build, 2. iounmap it, pte0 will set to 0; 3. ioremap the same address with 2M size, pgd/pmd is unchanged, then set the a new value for pmd; 4. pte0 is leaked; 5. CPU may meet exception because the old pmd is still in TLB, which will lead to kernel panic. Fix it by skip setting up the huge I/O mappings when p4d/pud/pmd is zero. Reported-by: Lei Li Signed-off-by: Hanjun Guo Cc: Toshi Kani Cc: Mark Rutland Cc: Will Deacon Cc: Catalin Marinas Cc: Michal Hocko Cc: Andrew Morton Cc: Xuefeng Wang --- Not sure if this is the right direction, this patch has a obvious side effect that a mapped address with 4K will not back to 2M. I may miss something and just wrong, so this is just a RFC version, comments are welcomed. lib/ioremap.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/lib/ioremap.c b/lib/ioremap.c index b808a39..4e6f19a 100644 --- a/lib/ioremap.c +++ b/lib/ioremap.c @@ -89,7 +89,7 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr, do { next = pmd_addr_end(addr, end); - if (ioremap_pmd_enabled() && + if (ioremap_pmd_enabled() && pmd_none(*pmd) && ((next - addr) == PMD_SIZE) && IS_ALIGNED(phys_addr + addr, PMD_SIZE)) { if (pmd_set_huge(pmd, phys_addr + addr, prot)) @@ -115,7 +115,7 @@ static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr, do { next = pud_addr_end(addr, end); - if (ioremap_pud_enabled() && + if (ioremap_pud_enabled() && pud_none(*pud) && ((next - addr) == PUD_SIZE) && IS_ALIGNED(phys_addr + addr, PUD_SIZE)) { if (pud_set_huge(pud, phys_addr + addr, prot)) @@ -141,7 +141,7 @@ static inline int ioremap_p4d_range(pgd_t *pgd, unsigned long addr, do { next = p4d_addr_end(addr, end); - if (ioremap_p4d_enabled() && + if (ioremap_p4d_enabled() && p4d_none(*p4d) && ((next - addr) == P4D_SIZE) && IS_ALIGNED(phys_addr + addr, P4D_SIZE)) { if (p4d_set_huge(p4d, phys_addr + addr, prot)) -- 1.7.12.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org