riscv: Fix kfence now that the linear mapping can be backed by PUD/P4D/PGD
Commit Message
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 <alexghiti@rivosinc.com>
---
arch/riscv/include/asm/kfence.h | 33 -------------------------------
arch/riscv/mm/init.c | 35 ++++++++++++++++++++++++++++-----
2 files changed, 30 insertions(+), 38 deletions(-)
Comments
On Tue, 06 Jun 2023 15:04:44 +0200, Alexandre Ghiti wrote:
> 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().
>
> [...]
Applied, thanks!
[1/1] riscv: Fix kfence now that the linear mapping can be backed by PUD/P4D/PGD
https://git.kernel.org/palmer/c/25abe0db9243
Best regards,
Hello:
This patch was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <palmer@rivosinc.com>:
On Tue, 6 Jun 2023 15:04:44 +0200 you wrote:
> 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().
>
> [...]
Here is the summary with links:
- riscv: Fix kfence now that the linear mapping can be backed by PUD/P4D/PGD
https://git.kernel.org/riscv/c/25abe0db9243
You are awesome, thank you!
@@ -8,41 +8,8 @@
#include <asm-generic/pgalloc.h>
#include <asm/pgtable.h>
-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;
}
@@ -23,6 +23,7 @@
#ifdef CONFIG_RELOCATABLE
#include <linux/elf.h>
#endif
+#include <linux/kfence.h>
#include <asm/fixmap.h>
#include <asm/tlbflush.h>
@@ -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)