From 25abe0db92437fde463204c3e4eb5a71b62d6e5d Mon Sep 17 00:00:00 2001 From: Alexandre Ghiti Date: Tue, 6 Jun 2023 15:04:44 +0200 Subject: [PATCH 1/1] riscv: Fix kfence now that the linear mapping can be backed by PUD/P4D/PGD RISC-V Kfence implementation used to rely on the fact the linear mapping was backed by at most PMD hugepages, which is not true anymore since commit 3335068f8721 ("riscv: Use PUD/P4D/PGD pages for the linear mapping"). Instead of splitting PUD/P4D/PGD mappings afterwards, directly map the kfence pool region using PTE mappings by allocating this region before setup_vm_final(). Reported-by: syzbot+a74d57bddabbedd75135@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=a74d57bddabbedd75135 Fixes: 3335068f8721 ("riscv: Use PUD/P4D/PGD pages for the linear mapping") Signed-off-by: Alexandre Ghiti Link: https://lore.kernel.org/r/20230606130444.25090-1-alexghiti@rivosinc.com Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/kfence.h | 33 --------------------------------- arch/riscv/mm/init.c | 35 ++++++++++++++++++++++++++++++----- 2 files changed, 30 insertions(+), 38 deletions(-) diff --git a/arch/riscv/include/asm/kfence.h b/arch/riscv/include/asm/kfence.h index d887a54..0bbffd5 100644 --- a/arch/riscv/include/asm/kfence.h +++ b/arch/riscv/include/asm/kfence.h @@ -8,41 +8,8 @@ #include #include -static inline int split_pmd_page(unsigned long addr) -{ - int i; - unsigned long pfn = PFN_DOWN(__pa((addr & PMD_MASK))); - pmd_t *pmd = pmd_off_k(addr); - pte_t *pte = pte_alloc_one_kernel(&init_mm); - - if (!pte) - return -ENOMEM; - - for (i = 0; i < PTRS_PER_PTE; i++) - set_pte(pte + i, pfn_pte(pfn + i, PAGE_KERNEL)); - set_pmd(pmd, pfn_pmd(PFN_DOWN(__pa(pte)), PAGE_TABLE)); - - flush_tlb_kernel_range(addr, addr + PMD_SIZE); - return 0; -} - static inline bool arch_kfence_init_pool(void) { - int ret; - unsigned long addr; - pmd_t *pmd; - - for (addr = (unsigned long)__kfence_pool; is_kfence_address((void *)addr); - addr += PAGE_SIZE) { - pmd = pmd_off_k(addr); - - if (pmd_leaf(*pmd)) { - ret = split_pmd_page(addr); - if (ret) - return false; - } - } - return true; } diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 0fe75c9..38c4b4d 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -23,6 +23,7 @@ #ifdef CONFIG_RELOCATABLE #include #endif +#include #include #include @@ -1167,14 +1168,16 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) } static void __init create_linear_mapping_range(phys_addr_t start, - phys_addr_t end) + phys_addr_t end, + uintptr_t fixed_map_size) { phys_addr_t pa; uintptr_t va, map_size; for (pa = start; pa < end; pa += map_size) { va = (uintptr_t)__va(pa); - map_size = best_map_size(pa, end - pa); + map_size = fixed_map_size ? fixed_map_size : + best_map_size(pa, end - pa); create_pgd_mapping(swapper_pg_dir, va, pa, map_size, pgprot_from_va(va)); @@ -1184,6 +1187,7 @@ static void __init create_linear_mapping_range(phys_addr_t start, static void __init create_linear_mapping_page_table(void) { phys_addr_t start, end; + phys_addr_t kfence_pool __maybe_unused; u64 i; #ifdef CONFIG_STRICT_KERNEL_RWX @@ -1197,6 +1201,19 @@ static void __init create_linear_mapping_page_table(void) memblock_mark_nomap(krodata_start, krodata_size); #endif +#ifdef CONFIG_KFENCE + /* + * kfence pool must be backed by PAGE_SIZE mappings, so allocate it + * before we setup the linear mapping so that we avoid using hugepages + * for this region. + */ + kfence_pool = memblock_phys_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); + BUG_ON(!kfence_pool); + + memblock_mark_nomap(kfence_pool, KFENCE_POOL_SIZE); + __kfence_pool = __va(kfence_pool); +#endif + /* Map all memory banks in the linear mapping */ for_each_mem_range(i, &start, &end) { if (start >= end) @@ -1207,17 +1224,25 @@ static void __init create_linear_mapping_page_table(void) if (end >= __pa(PAGE_OFFSET) + memory_limit) end = __pa(PAGE_OFFSET) + memory_limit; - create_linear_mapping_range(start, end); + create_linear_mapping_range(start, end, 0); } #ifdef CONFIG_STRICT_KERNEL_RWX - create_linear_mapping_range(ktext_start, ktext_start + ktext_size); + create_linear_mapping_range(ktext_start, ktext_start + ktext_size, 0); create_linear_mapping_range(krodata_start, - krodata_start + krodata_size); + krodata_start + krodata_size, 0); memblock_clear_nomap(ktext_start, ktext_size); memblock_clear_nomap(krodata_start, krodata_size); #endif + +#ifdef CONFIG_KFENCE + create_linear_mapping_range(kfence_pool, + kfence_pool + KFENCE_POOL_SIZE, + PAGE_SIZE); + + memblock_clear_nomap(kfence_pool, KFENCE_POOL_SIZE); +#endif } static void __init setup_vm_final(void) -- 2.7.4