[PATCH v3] riscv: mm: Fix the out of bound issue of vmemmap address
Björn Töpel
bjorn at kernel.org
Mon Dec 9 03:03:11 PST 2024
Minor nits below; Too many ifdefs.
Xu Lu <luxu.kernel at bytedance.com> writes:
> In sparse vmemmap model, the virtual address of vmemmap is calculated as:
> ((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT)).
> And the struct page's va can be calculated with an offset:
> (vmemmap + (pfn)).
>
> However, when initializing struct pages, kernel actually starts from the
> first page from the same section that phys_ram_base belongs to. If the
> first page's physical address is not (phys_ram_base >> PAGE_SHIFT), then
> we get an va below VMEMMAP_START when calculating va for it's struct page.
>
> For example, if phys_ram_base starts from 0x82000000 with pfn 0x82000, the
> first page in the same section is actually pfn 0x80000. During
> init_unavailable_range(), we will initialize struct page for pfn 0x80000
> with virtual address ((struct page *)VMEMMAP_START - 0x2000), which is
> below VMEMMAP_START as well as PCI_IO_END.
>
> This commit fixes this bug by introducing a new variable
> 'vmemmap_start_pfn' which is aligned with memory section size and using
> it to calculate vmemmap address instead of phys_ram_base.
>
> Fixes: a11dd49dcb93 ("riscv: Sparse-Memory/vmemmap out-of-bounds fix")
> Signed-off-by: Xu Lu <luxu.kernel at bytedance.com>
> ---
> arch/riscv/include/asm/page.h | 4 ++++
> arch/riscv/include/asm/pgtable.h | 4 +++-
> arch/riscv/mm/init.c | 18 ++++++++++++++++++
> 3 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> index 71aabc5c6713..a1be1adcfb85 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -123,6 +123,10 @@ struct kernel_mapping {
> extern struct kernel_mapping kernel_map;
> extern phys_addr_t phys_ram_base;
>
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
Not needed, and should be removed.
> +extern unsigned long vmemmap_start_pfn;
> +#endif
> +
> #define is_kernel_mapping(x) \
> ((x) >= kernel_map.virt_addr && (x) < (kernel_map.virt_addr + kernel_map.size))
>
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index d4e99eef90ac..e2dbd4b9a686 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -87,7 +87,9 @@
> * Define vmemmap for pfn_to_page & page_to_pfn calls. Needed if kernel
> * is configured with CONFIG_SPARSEMEM_VMEMMAP enabled.
> */
> -#define vmemmap ((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT))
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
Dito, please remove.
> +#define vmemmap ((struct page *)VMEMMAP_START - vmemmap_start_pfn)
> +#endif
>
> #define PCI_IO_SIZE SZ_16M
> #define PCI_IO_END VMEMMAP_START
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 0e8c20adcd98..e7c52d647f50 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -32,6 +32,9 @@
> #include <asm/numa.h>
> #include <asm/pgtable.h>
> #include <asm/sections.h>
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
Not needed, please remove.
> +#include <asm/sparsemem.h>
> +#endif
> #include <asm/soc.h>
> #include <asm/tlbflush.h>
>
> @@ -62,6 +65,13 @@ EXPORT_SYMBOL(pgtable_l5_enabled);
> phys_addr_t phys_ram_base __ro_after_init;
> EXPORT_SYMBOL(phys_ram_base);
>
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> +#define VMEMMAP_ADDR_ALIGN (1ULL << SECTION_SIZE_BITS)
> +
> +unsigned long vmemmap_start_pfn __ro_after_init;
> +EXPORT_SYMBOL(vmemmap_start_pfn);
> +#endif
> +
> unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
> __page_aligned_bss;
> EXPORT_SYMBOL(empty_zero_page);
> @@ -243,6 +253,11 @@ static void __init setup_bootmem(void)
> if (!IS_ENABLED(CONFIG_XIP_KERNEL))
> phys_ram_base = memblock_start_of_DRAM() & PMD_MASK;
>
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> + if (!IS_ENABLED(CONFIG_XIP_KERNEL))
> + vmemmap_start_pfn = round_down(phys_ram_base, VMEMMAP_ADDR_ALIGN) >> PAGE_SHIFT;
> +#endif
> +
Please fold this into the if-statement above, e.g.:
| if (!IS_ENABLED(CONFIG_XIP_KERNEL)) {
| phys_ram_base = memblock_start_of_DRAM() & PMD_MASK;
| #if defined(CONFIG_SPARSEMEM_VMEMMAP)
| vmemmap_start_pfn = round_down(phys_ram_base, VMEMMAP_ADDR_ALIGN) >> PAGE_SHIFT;
| #endif
| }
Björn
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