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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id h9-20020a056000000900b002f9e04459desm12759236wrx.109.2023.06.06.06.04.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Jun 2023 06:04:48 -0700 (PDT) From: Alexandre Ghiti To: Alexander Potapenko , Marco Elver , Dmitry Vyukov , Paul Walmsley , Palmer Dabbelt , Albert Ou , Rob Herring , Anup Patel , Alexandre Ghiti , Andrew Jones , kasan-dev@googlegroups.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Cc: syzbot+a74d57bddabbedd75135@syzkaller.appspotmail.com Subject: [PATCH] riscv: Fix kfence now that the linear mapping can be backed by PUD/P4D/PGD Date: Tue, 6 Jun 2023 15:04:44 +0200 Message-Id: <20230606130444.25090-1-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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=3Da74d57bddabbedd75135 Fixes: 3335068f8721 ("riscv: Use PUD/P4D/PGD pages for the linear mapping") Signed-off-by: Alexandre Ghiti --- 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/kfenc= e.h index d887a54042aa..0bbffd528096 100644 --- a/arch/riscv/include/asm/kfence.h +++ b/arch/riscv/include/asm/kfence.h @@ -8,41 +8,8 @@ #include #include =20 -static inline int split_pmd_page(unsigned long addr) -{ - int i; - unsigned long pfn =3D PFN_DOWN(__pa((addr & PMD_MASK))); - pmd_t *pmd =3D pmd_off_k(addr); - pte_t *pte =3D pte_alloc_one_kernel(&init_mm); - - if (!pte) - return -ENOMEM; - - for (i =3D 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 =3D (unsigned long)__kfence_pool; is_kfence_address((void *)add= r); - addr +=3D PAGE_SIZE) { - pmd =3D pmd_off_k(addr); - - if (pmd_leaf(*pmd)) { - ret =3D split_pmd_page(addr); - if (ret) - return false; - } - } - return true; } =20 diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 747e5b1ef02d..d42ea31c7de0 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -23,6 +23,7 @@ #ifdef CONFIG_RELOCATABLE #include #endif +#include =20 #include #include @@ -1167,14 +1168,16 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) } =20 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; =20 for (pa =3D start; pa < end; pa +=3D map_size) { va =3D (uintptr_t)__va(pa); - map_size =3D best_map_size(pa, end - pa); + map_size =3D fixed_map_size ? fixed_map_size : + best_map_size(pa, end - pa); =20 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_a= ddr_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; =20 #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 =20 +#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 =3D memblock_phys_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); + BUG_ON(!kfence_pool); + + memblock_mark_nomap(kfence_pool, KFENCE_POOL_SIZE); + __kfence_pool =3D __va(kfence_pool); +#endif + /* Map all memory banks in the linear mapping */ for_each_mem_range(i, &start, &end) { if (start >=3D end) @@ -1207,17 +1224,25 @@ static void __init create_linear_mapping_page_table= (void) if (end >=3D __pa(PAGE_OFFSET) + memory_limit) end =3D __pa(PAGE_OFFSET) + memory_limit; =20 - create_linear_mapping_range(start, end); + create_linear_mapping_range(start, end, 0); } =20 #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); =20 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 } =20 static void __init setup_vm_final(void) --=20 2.39.2