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[209.6.122.159]) by smtp.gmail.com with ESMTPSA id i66sm4234340qkb.105.2019.11.01.18.09.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 Nov 2019 18:09:35 -0700 (PDT) From: Masayoshi Mizuma To: Borislav Petkov , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Baoquan He Cc: Masayoshi Mizuma , Masayoshi Mizuma , linux-kernel@vger.kernel.org Subject: [PATCH v4 4/4] x86/mm/KASLR: Adjust the padding size for the direct mapping. Date: Fri, 1 Nov 2019 21:09:11 -0400 Message-Id: <20191102010911.21460-5-msys.mizuma@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191102010911.21460-1-msys.mizuma@gmail.com> References: <20191102010911.21460-1-msys.mizuma@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Masayoshi Mizuma The system sometimes crashes while memory hot-adding on KASLR enabled system. The crash happens because the regions pointed by kaslr_regions[].base are overwritten by the hot-added memory. It happens because of the padding size for kaslr_regions[].base isn't enough for the system whose physical memory layout has huge space for memory hotplug. kaslr_regions[].base points "actual installed memory size + padding" or higher address. So, if the "actual + padding" is lower address than the maximum memory address, which means the memory address reachable by memory hot-add, kaslr_regions[].base is destroyed by the overwritten. address ^ |------- maximum memory address (Hotplug) | ^ |------- kaslr_regions[0].base | Hotadd-able region | ^ | | | padding | | V V |------- actual memory address (Installed on boot) | Fix it by getting the maximum memory address from SRAT and store the value in boot_param, then set the padding size while KASLR initializing if the default padding size isn't enough. Signed-off-by: Baoquan He Signed-off-by: Masayoshi Mizuma --- arch/x86/mm/kaslr.c | 65 ++++++++++++++++++++++++++++++++++----------- 1 file changed, 50 insertions(+), 15 deletions(-) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index dc6182eec..a80eed563 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -70,15 +70,60 @@ static inline bool kaslr_memory_enabled(void) return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN); } +/* + * Even though a huge virtual address space is reserved for the direct + * mapping of physical memory, e.g in 4-level paging mode, it's 64TB, + * rare system can own enough physical memory to use it up, most are + * even less than 1TB. So with KASLR enabled, we adapt the size of + * direct mapping area to the size of actual physical memory plus the + * configured padding CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING. + * The left part will be taken out to join memory randomization. + */ +static inline unsigned long calc_direct_mapping_size(void) +{ + unsigned long padding = CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING; + unsigned long size_tb, memory_tb; +#ifdef CONFIG_MEMORY_HOTPLUG + unsigned long actual, maximum, base; + + if (boot_params.max_addr) { + /* + * The padding size should set to get for kaslr_regions[].base + * bigger address than the maximum memory address the system can + * have. kaslr_regions[].base points "actual size + padding" or + * higher address. If "actual size + padding" points the lower + * address than the maximum memory size, fix the padding size. + */ + actual = roundup(PFN_PHYS(max_pfn), 1UL << TB_SHIFT); + maximum = roundup(boot_params.max_addr, 1UL << TB_SHIFT); + base = actual + (padding << TB_SHIFT); + + if (maximum > base) + padding = (maximum - actual) >> TB_SHIFT; + } +#endif + memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + + padding; + + size_tb = 1 << (MAX_PHYSMEM_BITS - TB_SHIFT); + + /* + * Adapt physical memory region size based on available memory + */ + if (memory_tb < size_tb) + size_tb = memory_tb; + + return size_tb; +} + /* Initialize base and padding for each memory region randomized with KASLR */ void __init kernel_randomize_memory(void) { - size_t i; - unsigned long vaddr_start, vaddr; - unsigned long rand, memory_tb; - struct rnd_state rand_state; + unsigned long vaddr_start, vaddr, rand; unsigned long remain_entropy; unsigned long vmemmap_size; + struct rnd_state rand_state; + size_t i; vaddr_start = pgtable_l5_enabled() ? __PAGE_OFFSET_BASE_L5 : __PAGE_OFFSET_BASE_L4; vaddr = vaddr_start; @@ -95,20 +140,10 @@ void __init kernel_randomize_memory(void) if (!kaslr_memory_enabled()) return; - kaslr_regions[0].size_tb = 1 << (MAX_PHYSMEM_BITS - TB_SHIFT); + kaslr_regions[0].size_tb = calc_direct_mapping_size(); kaslr_regions[1].size_tb = VMALLOC_SIZE_TB; - /* - * Update Physical memory mapping to available and - * add padding if needed (especially for memory hotplug support). - */ BUG_ON(kaslr_regions[0].base != &page_offset_base); - memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + - CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING; - - /* Adapt phyiscal memory region size based on available memory */ - if (memory_tb < kaslr_regions[0].size_tb) - kaslr_regions[0].size_tb = memory_tb; /* * Calculate the vmemmap region size in TBs, aligned to a TB -- 2.20.1