From 9231ac48e1fb194977a88490e18dac1a0fb3ccc9 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 10 Aug 2021 16:27:17 +0800 Subject: [PATCH] arm64: mm: account for hotplug memory when randomizing the linear region mainline inclusion from mainline-v5.11-rc1 commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e category: bugfix bugzilla: 175103 CVE: NA ----------------------------------------------- As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical memory inside the linear region is chosen early at boot, it is based on the memblock description of memory, which does not cover hotplug memory. The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed. So let's limit this randomization of the linear region to ensure that this can no longer happen, by using the CPU's addressable PA range instead. As it is guaranteed that no hotpluggable memory will appear that falls outside of that range, we can safely put this PA range sized window anywhere in the linear region. Signed-off-by: Ard Biesheuvel Cc: Anshuman Khandual Cc: Will Deacon Cc: Steven Price Cc: Robin Murphy Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas Signed-off-by: Peng Liu Reviewed-by: Kefeng Wang Signed-off-by: Yang Yingliang --- arch/arm64/mm/init.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 957cc293226a..2399a257eaf3 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -683,15 +683,18 @@ void __init arm64_memblock_init(void) if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { extern u16 memstart_offset_seed; - u64 range = linear_region_size - - (memblock_end_of_DRAM() - memblock_start_of_DRAM()); + u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1); + int parange = cpuid_feature_extract_unsigned_field( + mmfr0, ID_AA64MMFR0_PARANGE_SHIFT); + s64 range = linear_region_size - + BIT(id_aa64mmfr0_parange_to_phys_shift(parange)); /* * If the size of the linear region exceeds, by a sufficient - * margin, the size of the region that the available physical - * memory spans, randomize the linear region as well. + * margin, the size of the region that the physical memory can + * span, randomize the linear region as well. */ - if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) { + if (memstart_offset_seed > 0 && range >= (s64)ARM64_MEMSTART_ALIGN) { range /= ARM64_MEMSTART_ALIGN; memstart_addr -= ARM64_MEMSTART_ALIGN * ((range * memstart_offset_seed) >> 16); -- GitLab