Messages in this thread | | | Date | Sun, 17 Nov 2019 08:42:16 +0800 | From | Baoquan He <> | Subject | Re: [PATCH v5 4/4] x86/mm/KASLR: Adjust the padding size for the direct mapping. |
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On 11/15/19 at 09:49am, Masayoshi Mizuma wrote: > From: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com> > > 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 <bhe@redhat.com> > Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com> > --- > arch/x86/mm/kaslr.c | 57 +++++++++++++++++++++++++++++++++------------ > 1 file changed, 42 insertions(+), 15 deletions(-) > > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > index dc6182eecefa..1f0aa9e68226 100644 > --- a/arch/x86/mm/kaslr.c > +++ b/arch/x86/mm/kaslr.c > @@ -70,15 +70,52 @@ 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.
The doc doesn't reflect the the case of boot_params.max_addr existed?
Otherwise, it looks good to me and easy to understand. You can remove my 'Signed-off' and feel free to add my ack.
Acked-by: Baoquan He <bhe@redhat.com>
Thanks Baoquan
> + */ > +static inline unsigned long calc_direct_mapping_size(void) > +{ > + unsigned long size_tb, memory_tb; > + > + memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + > + CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING; > + > +#ifdef CONFIG_MEMORY_HOTPLUG > + if (boot_params.max_addr) { > + unsigned long maximum_tb; > + > + maximum_tb = DIV_ROUND_UP(boot_params.max_addr, > + 1UL << TB_SHIFT); > + > + if (maximum_tb > memory_tb) > + memory_tb = maximum_tb; > + } > +#endif > + 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 +132,10 @@ 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 >
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