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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 3335068f87 ("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: 3335068f87 ("riscv: Use PUD/P4D/PGD pages for the linear mapping")
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20230606130444.25090-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Alexandre Ghiti 2023-06-06 15:04:44 +02:00 committed by Palmer Dabbelt
parent 6569fc12e4
commit 25abe0db92
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
2 changed files with 30 additions and 38 deletions
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33
arch/riscv/include/asm/kfence.h
View File

@ -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;
}

35
arch/riscv/mm/init.c
View File

@ -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)