When STRICT_KERNEL_RWX is set, any change of permissions on any kernel
mapping (vmalloc/modules/kernel text...etc) should be applied on its
linear mapping alias. The problem is that the riscv kernel uses huge
mappings for the linear mapping and walk_page_range_novma() does not
split those huge mappings.
So this patchset implements such split in order to apply fine-grained
permissions on the linear mapping.
Below is the difference before and after (the first PUD mapping is split
into PTE/PMD mappings):
Before:
---[ Linear mapping ]---
0xffffaf8000080000-0xffffaf8000200000 0x0000000080080000 1536K PTE D A G . . W R V
0xffffaf8000200000-0xffffaf8077c00000 0x0000000080200000 1914M PMD D A G . . W R V
0xffffaf8077c00000-0xffffaf8078800000 0x00000000f7c00000 12M PMD D A G . . . R V
0xffffaf8078800000-0xffffaf8078c00000 0x00000000f8800000 4M PMD D A G . . W R V
0xffffaf8078c00000-0xffffaf8079200000 0x00000000f8c00000 6M PMD D A G . . . R V
0xffffaf8079200000-0xffffaf807e600000 0x00000000f9200000 84M PMD D A G . . W R V
0xffffaf807e600000-0xffffaf807e716000 0x00000000fe600000 1112K PTE D A G . . W R V
0xffffaf807e717000-0xffffaf807e71a000 0x00000000fe717000 12K PTE D A G . . W R V
0xffffaf807e71d000-0xffffaf807e71e000 0x00000000fe71d000 4K PTE D A G . . W R V
0xffffaf807e722000-0xffffaf807e800000 0x00000000fe722000 888K PTE D A G . . W R V
0xffffaf807e800000-0xffffaf807fe00000 0x00000000fe800000 22M PMD D A G . . W R V
0xffffaf807fe00000-0xffffaf807ff54000 0x00000000ffe00000 1360K PTE D A G . . W R V
0xffffaf807ff55000-0xffffaf8080000000 0x00000000fff55000 684K PTE D A G . . W R V
0xffffaf8080000000-0xffffaf8400000000 0x0000000100000000 14G PUD D A G . . W R V
After:
---[ Linear mapping ]---
0xffffaf8000080000-0xffffaf8000200000 0x0000000080080000 1536K PTE D A G . . W R V
0xffffaf8000200000-0xffffaf8077c00000 0x0000000080200000 1914M PMD D A G . . W R V
0xffffaf8077c00000-0xffffaf8078800000 0x00000000f7c00000 12M PMD D A G . . . R V
0xffffaf8078800000-0xffffaf8078a00000 0x00000000f8800000 2M PMD D A G . . W R V
0xffffaf8078a00000-0xffffaf8078c00000 0x00000000f8a00000 2M PTE D A G . . W R V
0xffffaf8078c00000-0xffffaf8079200000 0x00000000f8c00000 6M PMD D A G . . . R V
0xffffaf8079200000-0xffffaf807e600000 0x00000000f9200000 84M PMD D A G . . W R V
0xffffaf807e600000-0xffffaf807e716000 0x00000000fe600000 1112K PTE D A G . . W R V
0xffffaf807e717000-0xffffaf807e71a000 0x00000000fe717000 12K PTE D A G . . W R V
0xffffaf807e71d000-0xffffaf807e71e000 0x00000000fe71d000 4K PTE D A G . . W R V
0xffffaf807e722000-0xffffaf807e800000 0x00000000fe722000 888K PTE D A G . . W R V
0xffffaf807e800000-0xffffaf807fe00000 0x00000000fe800000 22M PMD D A G . . W R V
0xffffaf807fe00000-0xffffaf807ff54000 0x00000000ffe00000 1360K PTE D A G . . W R V
0xffffaf807ff55000-0xffffaf8080000000 0x00000000fff55000 684K PTE D A G . . W R V
0xffffaf8080000000-0xffffaf8080800000 0x0000000100000000 8M PMD D A G . . W R V
0xffffaf8080800000-0xffffaf8080af6000 0x0000000100800000 3032K PTE D A G . . W R V
0xffffaf8080af6000-0xffffaf8080af8000 0x0000000100af6000 8K PTE D A G . X . R V
0xffffaf8080af8000-0xffffaf8080c00000 0x0000000100af8000 1056K PTE D A G . . W R V
0xffffaf8080c00000-0xffffaf8081a00000 0x0000000100c00000 14M PMD D A G . . W R V
0xffffaf8081a00000-0xffffaf8081a40000 0x0000000101a00000 256K PTE D A G . . W R V
0xffffaf8081a40000-0xffffaf8081a44000 0x0000000101a40000 16K PTE D A G . X . R V
0xffffaf8081a44000-0xffffaf8081a52000 0x0000000101a44000 56K PTE D A G . . W R V
0xffffaf8081a52000-0xffffaf8081a54000 0x0000000101a52000 8K PTE D A G . X . R V
...
0xffffaf809e800000-0xffffaf80c0000000 0x000000011e800000 536M PMD D A G . . W R V
0xffffaf80c0000000-0xffffaf8400000000 0x0000000140000000 13G PUD D A G . . W R V
Note that this also fixes memfd_secret() syscall which uses
set_direct_map_invalid_noflush() and set_direct_map_default_noflush() to
remove the pages from the linear mapping. Below is the kernel page table
while a memfd_secret() syscall is running, you can see all the !valid
page table entries in the linear mapping:
...
0xffffaf8082240000-0xffffaf8082241000 0x0000000102240000 4K PTE D A G . . W R .
0xffffaf8082241000-0xffffaf8082250000 0x0000000102241000 60K PTE D A G . . W R V
0xffffaf8082250000-0xffffaf8082252000 0x0000000102250000 8K PTE D A G . . W R .
0xffffaf8082252000-0xffffaf8082256000 0x0000000102252000 16K PTE D A G . . W R V
0xffffaf8082256000-0xffffaf8082257000 0x0000000102256000 4K PTE D A G . . W R .
0xffffaf8082257000-0xffffaf8082258000 0x0000000102257000 4K PTE D A G . . W R V
0xffffaf8082258000-0xffffaf8082259000 0x0000000102258000 4K PTE D A G . . W R .
0xffffaf8082259000-0xffffaf808225a000 0x0000000102259000 4K PTE D A G . . W R V
0xffffaf808225a000-0xffffaf808225c000 0x000000010225a000 8K PTE D A G . . W R .
0xffffaf808225c000-0xffffaf8082266000 0x000000010225c000 40K PTE D A G . . W R V
0xffffaf8082266000-0xffffaf8082268000 0x0000000102266000 8K PTE D A G . . W R .
0xffffaf8082268000-0xffffaf8082284000 0x0000000102268000 112K PTE D A G . . W R V
0xffffaf8082284000-0xffffaf8082288000 0x0000000102284000 16K PTE D A G . . W R .
0xffffaf8082288000-0xffffaf808229c000 0x0000000102288000 80K PTE D A G . . W R V
0xffffaf808229c000-0xffffaf80822a0000 0x000000010229c000 16K PTE D A G . . W R .
0xffffaf80822a0000-0xffffaf80822a5000 0x00000001022a0000 20K PTE D A G . . W R V
0xffffaf80822a5000-0xffffaf80822a6000 0x00000001022a5000 4K PTE D A G . . . R V
0xffffaf80822a6000-0xffffaf80822ab000 0x00000001022a6000 20K PTE D A G . . W R V
...
And when the memfd_secret() fd is released, the linear mapping is
correctly reset:
...
0xffffaf8082240000-0xffffaf80822a5000 0x0000000102240000 404K PTE D A G . . W R V
0xffffaf80822a5000-0xffffaf80822a6000 0x00000001022a5000 4K PTE D A G . . . R V
0xffffaf80822a6000-0xffffaf80822af000 0x00000001022a6000 36K PTE D A G . . W R V
...
Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
---
arch/riscv/mm/pageattr.c | 270 +++++++++++++++++++++++++++++++++------
1 file changed, 230 insertions(+), 40 deletions(-)
diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index 161d0b34c2cb..fc5fc4f785c4 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -5,6 +5,7 @@
#include <linux/pagewalk.h>
#include <linux/pgtable.h>
+#include <linux/vmalloc.h>
#include <asm/tlbflush.h>
#include <asm/bitops.h>
#include <asm/set_memory.h>
@@ -25,19 +26,6 @@ static unsigned long set_pageattr_masks(unsigned long val, struct mm_walk *walk)
return new_val;
}
-static int pageattr_pgd_entry(pgd_t *pgd, unsigned long addr,
- unsigned long next, struct mm_walk *walk)
-{
- pgd_t val = READ_ONCE(*pgd);
-
- if (pgd_leaf(val)) {
- val = __pgd(set_pageattr_masks(pgd_val(val), walk));
- set_pgd(pgd, val);
- }
-
- return 0;
-}
-
static int pageattr_p4d_entry(p4d_t *p4d, unsigned long addr,
unsigned long next, struct mm_walk *walk)
{
@@ -96,7 +84,6 @@ static int pageattr_pte_hole(unsigned long addr, unsigned long next,
}
static const struct mm_walk_ops pageattr_ops = {
- .pgd_entry = pageattr_pgd_entry,
.p4d_entry = pageattr_p4d_entry,
.pud_entry = pageattr_pud_entry,
.pmd_entry = pageattr_pmd_entry,
@@ -105,12 +92,181 @@ static const struct mm_walk_ops pageattr_ops = {
.walk_lock = PGWALK_RDLOCK,
};
+#ifdef CONFIG_64BIT
+static int __split_linear_mapping_pmd(pud_t *pudp,
+ unsigned long vaddr, unsigned long end)
+{
+ pmd_t *pmdp;
+ unsigned long next;
+
+ pmdp = pmd_offset(pudp, vaddr);
+
+ do {
+ next = pmd_addr_end(vaddr, end);
+
+ if (next - vaddr >= PMD_SIZE &&
+ vaddr <= (vaddr & PMD_MASK) && end >= next)
+ continue;
+
+ if (pmd_leaf(*pmdp)) {
+ struct page *pte_page;
+ unsigned long pfn = _pmd_pfn(*pmdp);
+ pgprot_t prot = __pgprot(pmd_val(*pmdp) & ~_PAGE_PFN_MASK);
+ pte_t *ptep_new;
+ int i;
+
+ pte_page = alloc_page(GFP_KERNEL);
+ if (!pte_page)
+ return -ENOMEM;
+
+ ptep_new = (pte_t *)page_address(pte_page);
+ for (i = 0; i < PTRS_PER_PTE; ++i, ++ptep_new)
+ set_pte(ptep_new, pfn_pte(pfn + i, prot));
+
+ smp_wmb();
+
+ set_pmd(pmdp, pfn_pmd(page_to_pfn(pte_page), PAGE_TABLE));
+ }
+ } while (pmdp++, vaddr = next, vaddr != end);
+
+ return 0;
+}
+
+static int __split_linear_mapping_pud(p4d_t *p4dp,
+ unsigned long vaddr, unsigned long end)
+{
+ pud_t *pudp;
+ unsigned long next;
+ int ret;
+
+ pudp = pud_offset(p4dp, vaddr);
+
+ do {
+ next = pud_addr_end(vaddr, end);
+
+ if (next - vaddr >= PUD_SIZE &&
+ vaddr <= (vaddr & PUD_MASK) && end >= next)
+ continue;
+
+ if (pud_leaf(*pudp)) {
+ struct page *pmd_page;
+ unsigned long pfn = _pud_pfn(*pudp);
+ pgprot_t prot = __pgprot(pud_val(*pudp) & ~_PAGE_PFN_MASK);
+ pmd_t *pmdp_new;
+ int i;
+
+ pmd_page = alloc_page(GFP_KERNEL);
+ if (!pmd_page)
+ return -ENOMEM;
+
+ pmdp_new = (pmd_t *)page_address(pmd_page);
+ for (i = 0; i < PTRS_PER_PMD; ++i, ++pmdp_new)
+ set_pmd(pmdp_new,
+ pfn_pmd(pfn + ((i * PMD_SIZE) >> PAGE_SHIFT), prot));
+
+ smp_wmb();
+
+ set_pud(pudp, pfn_pud(page_to_pfn(pmd_page), PAGE_TABLE));
+ }
+
+ ret = __split_linear_mapping_pmd(pudp, vaddr, next);
+ if (ret)
+ return ret;
+ } while (pudp++, vaddr = next, vaddr != end);
+
+ return 0;
+}
+
+static int __split_linear_mapping_p4d(pgd_t *pgdp,
+ unsigned long vaddr, unsigned long end)
+{
+ p4d_t *p4dp;
+ unsigned long next;
+ int ret;
+
+ p4dp = p4d_offset(pgdp, vaddr);
+
+ do {
+ next = p4d_addr_end(vaddr, end);
+
+ /*
+ * If [vaddr; end] contains [vaddr & P4D_MASK; next], we don't
+ * need to split, we'll change the protections on the whole P4D.
+ */
+ if (next - vaddr >= P4D_SIZE &&
+ vaddr <= (vaddr & P4D_MASK) && end >= next)
+ continue;
+
+ if (p4d_leaf(*p4dp)) {
+ struct page *pud_page;
+ unsigned long pfn = _p4d_pfn(*p4dp);
+ pgprot_t prot = __pgprot(p4d_val(*p4dp) & ~_PAGE_PFN_MASK);
+ pud_t *pudp_new;
+ int i;
+
+ pud_page = alloc_page(GFP_KERNEL);
+ if (!pud_page)
+ return -ENOMEM;
+
+ /*
+ * Fill the pud level with leaf puds that have the same
+ * protections as the leaf p4d.
+ */
+ pudp_new = (pud_t *)page_address(pud_page);
+ for (i = 0; i < PTRS_PER_PUD; ++i, ++pudp_new)
+ set_pud(pudp_new,
+ pfn_pud(pfn + ((i * PUD_SIZE) >> PAGE_SHIFT), prot));
+
+ /*
+ * Make sure the pud filling is not reordered with the
+ * p4d store which could result in seeing a partially
+ * filled pud level.
+ */
+ smp_wmb();
+
+ set_p4d(p4dp, pfn_p4d(page_to_pfn(pud_page), PAGE_TABLE));
+ }
+
+ ret = __split_linear_mapping_pud(p4dp, vaddr, next);
+ if (ret)
+ return ret;
+ } while (p4dp++, vaddr = next, vaddr != end);
+
+ return 0;
+}
+
+static int __split_linear_mapping_pgd(pgd_t *pgdp,
+ unsigned long vaddr,
+ unsigned long end)
+{
+ unsigned long next;
+ int ret;
+
+ do {
+ next = pgd_addr_end(vaddr, end);
+ /* We never use PGD mappings for the linear mapping */
+ ret = __split_linear_mapping_p4d(pgdp, vaddr, next);
+ if (ret)
+ return ret;
+ } while (pgdp++, vaddr = next, vaddr != end);
+
+ return 0;
+}
+
+static int split_linear_mapping(unsigned long start, unsigned long end)
+{
+ return __split_linear_mapping_pgd(pgd_offset_k(start), start, end);
+}
+#endif /* CONFIG_64BIT */
+
static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask,
pgprot_t clear_mask)
{
int ret;
unsigned long start = addr;
unsigned long end = start + PAGE_SIZE * numpages;
+ unsigned long __maybe_unused lm_start;
+ unsigned long __maybe_unused lm_end;
struct pageattr_masks masks = {
.set_mask = set_mask,
.clear_mask = clear_mask
@@ -120,11 +276,67 @@ static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask,
return 0;
mmap_write_lock(&init_mm);
+
+#ifdef CONFIG_64BIT
+ /*
+ * We are about to change the permissions of a kernel mapping, we must
+ * apply the same changes to its linear mapping alias, which may imply
+ * splitting a huge mapping.
+ */
+
+ if (is_vmalloc_or_module_addr((void *)start)) {
+ struct vm_struct *area = NULL;
+ int i, page_start;
+
+ area = find_vm_area((void *)start);
+ page_start = (start - (unsigned long)area->addr) >> PAGE_SHIFT;
+
+ for (i = page_start; i < page_start + numpages; ++i) {
+ lm_start = (unsigned long)page_address(area->pages[i]);
+ lm_end = lm_start + PAGE_SIZE;
+
+ ret = split_linear_mapping(lm_start, lm_end);
+ if (ret)
+ goto unlock;
+
+ ret = walk_page_range_novma(&init_mm, lm_start, lm_end,
+ &pageattr_ops, NULL, &masks);
+ if (ret)
+ goto unlock;
+ }
+ } else if (is_kernel_mapping(start) || is_linear_mapping(start)) {
+ lm_start = (unsigned long)lm_alias(start);
+ lm_end = (unsigned long)lm_alias(end);
+
+ ret = split_linear_mapping(lm_start, lm_end);
+ if (ret)
+ goto unlock;
+
+ ret = walk_page_range_novma(&init_mm, lm_start, lm_end,
+ &pageattr_ops, NULL, &masks);
+ if (ret)
+ goto unlock;
+ }
+
ret = walk_page_range_novma(&init_mm, start, end, &pageattr_ops, NULL,
&masks);
+
+unlock:
+ mmap_write_unlock(&init_mm);
+
+ /*
+ * We can't use flush_tlb_kernel_range() here as we may have split a
+ * hugepage that is larger than that, so let's flush everything.
+ */
+ flush_tlb_all();
+#else
+ ret = walk_page_range_novma(&init_mm, start, end, &pageattr_ops, NULL,
+ &masks);
+
mmap_write_unlock(&init_mm);
flush_tlb_kernel_range(start, end);
+#endif
return ret;
}
@@ -159,36 +371,14 @@ int set_memory_nx(unsigned long addr, int numpages)
int set_direct_map_invalid_noflush(struct page *page)
{
- int ret;
- unsigned long start = (unsigned long)page_address(page);
- unsigned long end = start + PAGE_SIZE;
- struct pageattr_masks masks = {
- .set_mask = __pgprot(0),
- .clear_mask = __pgprot(_PAGE_PRESENT)
- };
-
- mmap_read_lock(&init_mm);
- ret = walk_page_range(&init_mm, start, end, &pageattr_ops, &masks);
- mmap_read_unlock(&init_mm);
-
- return ret;
+ return __set_memory((unsigned long)page_address(page), 1,
+ __pgprot(0), __pgprot(_PAGE_PRESENT));
}
int set_direct_map_default_noflush(struct page *page)
{
- int ret;
- unsigned long start = (unsigned long)page_address(page);
- unsigned long end = start + PAGE_SIZE;
- struct pageattr_masks masks = {
- .set_mask = PAGE_KERNEL,
- .clear_mask = __pgprot(0)
- };
-
- mmap_read_lock(&init_mm);
- ret = walk_page_range(&init_mm, start, end, &pageattr_ops, &masks);
- mmap_read_unlock(&init_mm);
-
- return ret;
+ return __set_memory((unsigned long)page_address(page), 1,
+ PAGE_KERNEL, __pgprot(0));
}
#ifdef CONFIG_DEBUG_PAGEALLOC
--
2.39.2
