From: Joerg Roedel jroedel@suse.de Subject: mm: track page table modifications in __apply_to_page_range()
__apply_to_page_range() is also used to change and/or allocate page-table pages in the vmalloc area of the address space. Make sure these changes get synchronized to other page-tables in the system by calling arch_sync_kernel_mappings() when necessary.
The impact appears limited to x86-32, where apply_to_page_range may miss updating the PMD. That leads to explosions in drivers like
[ 24.227844] BUG: unable to handle page fault for address: fe036000 [ 24.228076] #PF: supervisor write access in kernel mode [ 24.228294] #PF: error_code(0x0002) - not-present page [ 24.228494] *pde = 00000000 [ 24.228640] Oops: 0002 [#1] SMP [ 24.228788] CPU: 3 PID: 1300 Comm: gem_concurrent_ Not tainted 5.9.0-rc1+ #16 [ 24.228957] Hardware name: /NUC6i3SYB, BIOS SYSKLi35.86A.0024.2015.1027.2142 10/27/2015 [ 24.229297] EIP: __execlists_context_alloc+0x132/0x2d0 [i915] [ 24.229462] Code: 31 d2 89 f0 e8 2f 55 02 00 89 45 e8 3d 00 f0 ff ff 0f 87 11 01 00 00 8b 4d e8 03 4b 30 b8 5a 5a 5a 5a ba 01 00 00 00 8d 79 04 <c7> 01 5a 5a 5a 5a c7 81 fc 0f 00 00 5a 5a 5a 5a 83 e7 fc 29 f9 81 [ 24.229759] EAX: 5a5a5a5a EBX: f60ca000 ECX: fe036000 EDX: 00000001 [ 24.229915] ESI: f43b7340 EDI: fe036004 EBP: f6389cb8 ESP: f6389c9c [ 24.230072] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010286 [ 24.230229] CR0: 80050033 CR2: fe036000 CR3: 2d361000 CR4: 001506d0 [ 24.230385] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 [ 24.230539] DR6: fffe0ff0 DR7: 00000400 [ 24.230675] Call Trace: [ 24.230957] execlists_context_alloc+0x10/0x20 [i915] [ 24.231266] intel_context_alloc_state+0x3f/0x70 [i915] [ 24.231547] __intel_context_do_pin+0x117/0x170 [i915] [ 24.231850] i915_gem_do_execbuffer+0xcc7/0x2500 [i915] [ 24.232024] ? __kmalloc_track_caller+0x54/0x230 [ 24.232181] ? ktime_get+0x3e/0x120 [ 24.232333] ? dma_fence_signal+0x34/0x50 [ 24.232617] i915_gem_execbuffer2_ioctl+0xcd/0x1f0 [i915] [ 24.232912] ? i915_gem_execbuffer_ioctl+0x2e0/0x2e0 [i915] [ 24.233084] drm_ioctl_kernel+0x8f/0xd0 [ 24.233236] drm_ioctl+0x223/0x3d0 [ 24.233505] ? i915_gem_execbuffer_ioctl+0x2e0/0x2e0 [i915] [ 24.233684] ? pick_next_task_fair+0x1b5/0x3d0 [ 24.233873] ? __switch_to_asm+0x36/0x50 [ 24.234021] ? drm_ioctl_kernel+0xd0/0xd0 [ 24.234167] __ia32_sys_ioctl+0x1ab/0x760 [ 24.234313] ? exit_to_user_mode_prepare+0xe5/0x110 [ 24.234453] ? syscall_exit_to_user_mode+0x23/0x130 [ 24.234601] __do_fast_syscall_32+0x3f/0x70 [ 24.234744] do_fast_syscall_32+0x29/0x60 [ 24.234885] do_SYSENTER_32+0x15/0x20 [ 24.235021] entry_SYSENTER_32+0x9f/0xf2 [ 24.235157] EIP: 0xb7f28559 [ 24.235288] Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d 76 00 58 b8 77 00 00 00 cd 80 90 8d 76 [ 24.235576] EAX: ffffffda EBX: 00000005 ECX: c0406469 EDX: bf95556c [ 24.235722] ESI: b7e68000 EDI: c0406469 EBP: 00000005 ESP: bf9554d8 [ 24.235869] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00000296 [ 24.236018] Modules linked in: i915 x86_pkg_temp_thermal intel_powerclamp crc32_pclmul crc32c_intel intel_cstate intel_uncore intel_gtt drm_kms_helper intel_pch_thermal video button autofs4 i2c_i801 i2c_smbus fan [ 24.236336] CR2: 00000000fe036000
It looks like kasan, xen and i915 are vulnerable.
Actual impact is "on thinkpad X60 in 5.9-rc1, screen starts blinking after 30-or-so minutes, and machine is unusable"
[sfr@canb.auug.org.au: ARCH_PAGE_TABLE_SYNC_MASK needs vmalloc.h] Link: https://lkml.kernel.org/r/20200825172508.16800a4f@canb.auug.org.au [chris@chris-wilson.co.uk: changelog addition] [pavel@ucw.cz: changelog addition] Link: https://lkml.kernel.org/r/20200821123746.16904-1-joro@8bytes.org Fixes: 2ba3e6947aed ("mm/vmalloc: track which page-table levels were modified") Fixes: 86cf69f1d893 ("x86/mm/32: implement arch_sync_kernel_mappings()") Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Stephen Rothwell sfr@canb.auug.org.au Tested-by: Chris Wilson chris@chris-wilson.co.uk [x86-32] Acked-by: Linus Torvalds torvalds@linux-foundation.org Tested-by: Pavel Machek pavel@ucw.cz Cc: stable@vger.kernel.org [5.8+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/memory.c | 37 ++++++++++++++++++++++++------------- 1 file changed, 24 insertions(+), 13 deletions(-)
--- a/mm/memory.c~mm-track-page-table-modifications-in-__apply_to_page_range +++ a/mm/memory.c @@ -73,6 +73,7 @@ #include <linux/numa.h> #include <linux/perf_event.h> #include <linux/ptrace.h> +#include <linux/vmalloc.h>
#include <trace/events/kmem.h>
@@ -83,6 +84,7 @@ #include <asm/tlb.h> #include <asm/tlbflush.h>
+#include "pgalloc-track.h" #include "internal.h"
#if defined(LAST_CPUPID_NOT_IN_PAGE_FLAGS) && !defined(CONFIG_COMPILE_TEST) @@ -2206,7 +2208,8 @@ EXPORT_SYMBOL(vm_iomap_memory);
static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd, unsigned long addr, unsigned long end, - pte_fn_t fn, void *data, bool create) + pte_fn_t fn, void *data, bool create, + pgtbl_mod_mask *mask) { pte_t *pte; int err = 0; @@ -2214,7 +2217,7 @@ static int apply_to_pte_range(struct mm_
if (create) { pte = (mm == &init_mm) ? - pte_alloc_kernel(pmd, addr) : + pte_alloc_kernel_track(pmd, addr, mask) : pte_alloc_map_lock(mm, pmd, addr, &ptl); if (!pte) return -ENOMEM; @@ -2235,6 +2238,7 @@ static int apply_to_pte_range(struct mm_ break; } } while (addr += PAGE_SIZE, addr != end); + *mask |= PGTBL_PTE_MODIFIED;
arch_leave_lazy_mmu_mode();
@@ -2245,7 +2249,8 @@ static int apply_to_pte_range(struct mm_
static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud, unsigned long addr, unsigned long end, - pte_fn_t fn, void *data, bool create) + pte_fn_t fn, void *data, bool create, + pgtbl_mod_mask *mask) { pmd_t *pmd; unsigned long next; @@ -2254,7 +2259,7 @@ static int apply_to_pmd_range(struct mm_ BUG_ON(pud_huge(*pud));
if (create) { - pmd = pmd_alloc(mm, pud, addr); + pmd = pmd_alloc_track(mm, pud, addr, mask); if (!pmd) return -ENOMEM; } else { @@ -2264,7 +2269,7 @@ static int apply_to_pmd_range(struct mm_ next = pmd_addr_end(addr, end); if (create || !pmd_none_or_clear_bad(pmd)) { err = apply_to_pte_range(mm, pmd, addr, next, fn, data, - create); + create, mask); if (err) break; } @@ -2274,14 +2279,15 @@ static int apply_to_pmd_range(struct mm_
static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d, unsigned long addr, unsigned long end, - pte_fn_t fn, void *data, bool create) + pte_fn_t fn, void *data, bool create, + pgtbl_mod_mask *mask) { pud_t *pud; unsigned long next; int err = 0;
if (create) { - pud = pud_alloc(mm, p4d, addr); + pud = pud_alloc_track(mm, p4d, addr, mask); if (!pud) return -ENOMEM; } else { @@ -2291,7 +2297,7 @@ static int apply_to_pud_range(struct mm_ next = pud_addr_end(addr, end); if (create || !pud_none_or_clear_bad(pud)) { err = apply_to_pmd_range(mm, pud, addr, next, fn, data, - create); + create, mask); if (err) break; } @@ -2301,14 +2307,15 @@ static int apply_to_pud_range(struct mm_
static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd, unsigned long addr, unsigned long end, - pte_fn_t fn, void *data, bool create) + pte_fn_t fn, void *data, bool create, + pgtbl_mod_mask *mask) { p4d_t *p4d; unsigned long next; int err = 0;
if (create) { - p4d = p4d_alloc(mm, pgd, addr); + p4d = p4d_alloc_track(mm, pgd, addr, mask); if (!p4d) return -ENOMEM; } else { @@ -2318,7 +2325,7 @@ static int apply_to_p4d_range(struct mm_ next = p4d_addr_end(addr, end); if (create || !p4d_none_or_clear_bad(p4d)) { err = apply_to_pud_range(mm, p4d, addr, next, fn, data, - create); + create, mask); if (err) break; } @@ -2331,8 +2338,9 @@ static int __apply_to_page_range(struct void *data, bool create) { pgd_t *pgd; - unsigned long next; + unsigned long start = addr, next; unsigned long end = addr + size; + pgtbl_mod_mask mask = 0; int err = 0;
if (WARN_ON(addr >= end)) @@ -2343,11 +2351,14 @@ static int __apply_to_page_range(struct next = pgd_addr_end(addr, end); if (!create && pgd_none_or_clear_bad(pgd)) continue; - err = apply_to_p4d_range(mm, pgd, addr, next, fn, data, create); + err = apply_to_p4d_range(mm, pgd, addr, next, fn, data, create, &mask); if (err) break; } while (pgd++, addr = next, addr != end);
+ if (mask & ARCH_PAGE_TABLE_SYNC_MASK) + arch_sync_kernel_mappings(start, start + size); + return err; }
_