diff mbox series

riscv: Fix kfence now that the linear mapping can be backed by PUD/P4D/PGD

Message ID 20230606130444.25090-1-alexghiti@rivosinc.com (mailing list archive)
State Accepted
Commit 25abe0db92437fde463204c3e4eb5a71b62d6e5d
Headers show
Series riscv: Fix kfence now that the linear mapping can be backed by PUD/P4D/PGD | expand

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conchuod/cover_letter success Single patches do not need cover letters
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conchuod/fixes_present success Fixes tag present in non-next series
conchuod/maintainers_pattern success MAINTAINERS pattern errors before the patch: 6 and now 6
conchuod/verify_signedoff success Signed-off-by tag matches author and committer
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conchuod/build_rv32_defconfig success Build OK
conchuod/dtb_warn_rv64 success Errors and warnings before: 3 this patch: 3
conchuod/header_inline success No static functions without inline keyword in header files
conchuod/checkpatch warning WARNING: Do not crash the kernel unless it is absolutely unavoidable--use WARN_ON_ONCE() plus recovery code (if feasible) instead of BUG() or variants
conchuod/build_rv64_nommu_k210_defconfig success Build OK
conchuod/verify_fixes success Fixes tag looks correct
conchuod/build_rv64_nommu_virt_defconfig success Build OK

Commit Message

Alexandre Ghiti June 6, 2023, 1:04 p.m. UTC 
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

Palmer Dabbelt June 8, 2023, 2:04 p.m. UTC | #1 
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,
patchwork-bot+linux-riscv@kernel.org June 8, 2023, 2:10 p.m. UTC | #2 
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!
diff mbox series

Patch

diff --git a/arch/riscv/include/asm/kfence.h b/arch/riscv/include/asm/kfence.h
index d887a54042aa..0bbffd528096 100644
--- a/arch/riscv/include/asm/kfence.h
+++ b/arch/riscv/include/asm/kfence.h
@@ -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;
 }
 
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 <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)