diff options
| -rw-r--r-- | arch/x86/kernel/tboot.c | 1 | ||||
| -rw-r--r-- | drivers/firmware/efi/efi.c | 1 | ||||
| -rw-r--r-- | include/linux/mm_types.h | 8 | ||||
| -rw-r--r-- | kernel/fork.c | 1 | ||||
| -rw-r--r-- | mm/gup.c | 18 | ||||
| -rw-r--r-- | mm/init-mm.c | 1 | ||||
| -rw-r--r-- | mm/memory.c | 13 |
7 files changed, 42 insertions, 1 deletions
diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c index ae64f98ec2ab..4c09ba110204 100644 --- a/arch/x86/kernel/tboot.c +++ b/arch/x86/kernel/tboot.c @@ -93,6 +93,7 @@ static struct mm_struct tboot_mm = { .pgd = swapper_pg_dir, .mm_users = ATOMIC_INIT(2), .mm_count = ATOMIC_INIT(1), + .write_protect_seq = SEQCNT_ZERO(tboot_mm.write_protect_seq), MMAP_LOCK_INITIALIZER(init_mm) .page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock), .mmlist = LIST_HEAD_INIT(init_mm.mmlist), diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index 6c6eec044a97..df3f9bcab581 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -57,6 +57,7 @@ struct mm_struct efi_mm = { .mm_rb = RB_ROOT, .mm_users = ATOMIC_INIT(2), .mm_count = ATOMIC_INIT(1), + .write_protect_seq = SEQCNT_ZERO(efi_mm.write_protect_seq), MMAP_LOCK_INITIALIZER(efi_mm) .page_table_lock = __SPIN_LOCK_UNLOCKED(efi_mm.page_table_lock), .mmlist = LIST_HEAD_INIT(efi_mm.mmlist), diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5a9238f6caad..915f4f100383 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -14,6 +14,7 @@ #include <linux/uprobes.h> #include <linux/page-flags-layout.h> #include <linux/workqueue.h> +#include <linux/seqlock.h> #include <asm/mmu.h> @@ -446,6 +447,13 @@ struct mm_struct { */ atomic_t has_pinned; + /** + * @write_protect_seq: Locked when any thread is write + * protecting pages mapped by this mm to enforce a later COW, + * for instance during page table copying for fork(). + */ + seqcount_t write_protect_seq; + #ifdef CONFIG_MMU atomic_long_t pgtables_bytes; /* PTE page table pages */ #endif diff --git a/kernel/fork.c b/kernel/fork.c index 6d266388d380..dc55f68a6ee3 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1007,6 +1007,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, mm->vmacache_seqnum = 0; atomic_set(&mm->mm_users, 1); atomic_set(&mm->mm_count, 1); + seqcount_init(&mm->write_protect_seq); mmap_init_lock(mm); INIT_LIST_HEAD(&mm->mmlist); mm->core_state = NULL; @@ -2684,11 +2684,18 @@ static unsigned long lockless_pages_from_mm(unsigned long start, { unsigned long flags; int nr_pinned = 0; + unsigned seq; if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) || !gup_fast_permitted(start, end)) return 0; + if (gup_flags & FOLL_PIN) { + seq = raw_read_seqcount(¤t->mm->write_protect_seq); + if (seq & 1) + return 0; + } + /* * Disable interrupts. The nested form is used, in order to allow full, * general purpose use of this routine. @@ -2703,6 +2710,17 @@ static unsigned long lockless_pages_from_mm(unsigned long start, local_irq_save(flags); gup_pgd_range(start, end, gup_flags, pages, &nr_pinned); local_irq_restore(flags); + + /* + * When pinning pages for DMA there could be a concurrent write protect + * from fork() via copy_page_range(), in this case always fail fast GUP. + */ + if (gup_flags & FOLL_PIN) { + if (read_seqcount_retry(¤t->mm->write_protect_seq, seq)) { + unpin_user_pages(pages, nr_pinned); + return 0; + } + } return nr_pinned; } diff --git a/mm/init-mm.c b/mm/init-mm.c index 3a613c85f9ed..153162669f80 100644 --- a/mm/init-mm.c +++ b/mm/init-mm.c @@ -31,6 +31,7 @@ struct mm_struct init_mm = { .pgd = swapper_pg_dir, .mm_users = ATOMIC_INIT(2), .mm_count = ATOMIC_INIT(1), + .write_protect_seq = SEQCNT_ZERO(init_mm.write_protect_seq), MMAP_LOCK_INITIALIZER(init_mm) .page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock), .arg_lock = __SPIN_LOCK_UNLOCKED(init_mm.arg_lock), diff --git a/mm/memory.c b/mm/memory.c index c48f8df6e502..50632c4366b8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1171,6 +1171,15 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, 0, src_vma, src_mm, addr, end); mmu_notifier_invalidate_range_start(&range); + /* + * Disabling preemption is not needed for the write side, as + * the read side doesn't spin, but goes to the mmap_lock. + * + * Use the raw variant of the seqcount_t write API to avoid + * lockdep complaining about preemptibility. + */ + mmap_assert_write_locked(src_mm); + raw_write_seqcount_begin(&src_mm->write_protect_seq); } ret = 0; @@ -1187,8 +1196,10 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) } } while (dst_pgd++, src_pgd++, addr = next, addr != end); - if (is_cow) + if (is_cow) { + raw_write_seqcount_end(&src_mm->write_protect_seq); mmu_notifier_invalidate_range_end(&range); + } return ret; } |