From: Lokesh Gidra <lokeshgidra@google.com> mainline inclusion from mainline-v6.9-rc1 commit 867a43a34ff8a38772212045262b2c9b77807ea3 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9183 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- All userfaultfd operations, except write-protect, opportunistically use per-vma locks to lock vmas. On failure, attempt again inside mmap_lock critical section. Write-protect operation requires mmap_lock as it iterates over multiple vmas. Link: https://lkml.kernel.org/r/20240215182756.3448972-5-lokeshgidra@google.com Signed-off-by: Lokesh Gidra <lokeshgidra@google.com> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Brian Geffon <bgeffon@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Nicolas Geoffray <ngeoffray@google.com> Cc: Peter Xu <peterx@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Tim Murray <timmurray@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Conflicts: mm/userfaultfd.c [conflicts due to uffd move not supported] Signed-off-by: Wupeng Ma <mawupeng1@huawei.com> --- mm/userfaultfd.c | 214 +++++++++++++++++++++++++++++++++-------------- 1 file changed, 150 insertions(+), 64 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 89d647037a5bd..d3505ee3a4131 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -22,19 +22,11 @@ #include "internal.h" static __always_inline -struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, - unsigned long dst_start, - unsigned long len) +bool validate_dst_vma(struct vm_area_struct *dst_vma, unsigned long dst_end) { - /* - * Make sure that the dst range is both valid and fully within a - * single existing vma. - */ - struct vm_area_struct *dst_vma; - - dst_vma = find_vma(dst_mm, dst_start); - if (!range_in_vma(dst_vma, dst_start, dst_start + len)) - return NULL; + /* Make sure that the dst range is fully within dst_vma. */ + if (dst_end > dst_vma->vm_end) + return false; /* * Check the vma is registered in uffd, this is required to @@ -42,11 +34,122 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, * time. */ if (!dst_vma->vm_userfaultfd_ctx.ctx) - return NULL; + return false; + + return true; +} + +static __always_inline +struct vm_area_struct *find_vma_and_prepare_anon(struct mm_struct *mm, + unsigned long addr) +{ + struct vm_area_struct *vma; + + mmap_assert_locked(mm); + vma = vma_lookup(mm, addr); + if (!vma) + vma = ERR_PTR(-ENOENT); + else if (!(vma->vm_flags & VM_SHARED) && + unlikely(anon_vma_prepare(vma))) + vma = ERR_PTR(-ENOMEM); + + return vma; +} + +#ifdef CONFIG_PER_VMA_LOCK +/* + * lock_vma() - Lookup and lock vma corresponding to @address. + * @mm: mm to search vma in. + * @address: address that the vma should contain. + * + * Should be called without holding mmap_lock. vma should be unlocked after use + * with unlock_vma(). + * + * Return: A locked vma containing @address, -ENOENT if no vma is found, or + * -ENOMEM if anon_vma couldn't be allocated. + */ +static struct vm_area_struct *lock_vma(struct mm_struct *mm, + unsigned long address) +{ + struct vm_area_struct *vma; + + vma = lock_vma_under_rcu(mm, address); + if (vma) { + /* + * lock_vma_under_rcu() only checks anon_vma for private + * anonymous mappings. But we need to ensure it is assigned in + * private file-backed vmas as well. + */ + if (!(vma->vm_flags & VM_SHARED) && unlikely(!vma->anon_vma)) + vma_end_read(vma); + else + return vma; + } + + mmap_read_lock(mm); + vma = find_vma_and_prepare_anon(mm, address); + if (!IS_ERR(vma)) { + /* + * We cannot use vma_start_read() as it may fail due to + * false locked (see comment in vma_start_read()). We + * can avoid that by directly locking vm_lock under + * mmap_lock, which guarantees that nobody can lock the + * vma for write (vma_start_write()) under us. + */ + down_read(&vma->vm_lock->lock); + } + + mmap_read_unlock(mm); + return vma; +} + +static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm, + unsigned long dst_start, + unsigned long len) +{ + struct vm_area_struct *dst_vma; + + dst_vma = lock_vma(dst_mm, dst_start); + if (IS_ERR(dst_vma) || validate_dst_vma(dst_vma, dst_start + len)) + return dst_vma; + + vma_end_read(dst_vma); + return ERR_PTR(-ENOENT); +} + +static void uffd_mfill_unlock(struct vm_area_struct *vma) +{ + vma_end_read(vma); +} + +#else + +static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm, + unsigned long dst_start, + unsigned long len) +{ + struct vm_area_struct *dst_vma; + + mmap_read_lock(dst_mm); + dst_vma = find_vma_and_prepare_anon(dst_mm, dst_start); + if (IS_ERR(dst_vma)) + goto out_unlock; + if (validate_dst_vma(dst_vma, dst_start + len)) + return dst_vma; + + dst_vma = ERR_PTR(-ENOENT); +out_unlock: + mmap_read_unlock(dst_mm); return dst_vma; } +static void uffd_mfill_unlock(struct vm_area_struct *vma) +{ + mmap_read_unlock(vma->vm_mm); +} +#endif + /* Check if dst_addr is outside of file's size. Must be called with ptl held. */ static bool mfill_file_over_size(struct vm_area_struct *dst_vma, unsigned long dst_addr) @@ -387,7 +490,8 @@ static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) #ifdef CONFIG_HUGETLB_PAGE /* * mfill_atomic processing for HUGETLB vmas. Note that this routine is - * called with mmap_lock held, it will release mmap_lock before returning. + * called with either vma-lock or mmap_lock held, it will release the lock + * before returning. */ static __always_inline ssize_t mfill_atomic_hugetlb( struct userfaultfd_ctx *ctx, @@ -398,7 +502,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb( uffd_flags_t flags) { struct mm_struct *dst_mm = dst_vma->vm_mm; - int vm_shared = dst_vma->vm_flags & VM_SHARED; ssize_t err; pte_t *dst_pte; unsigned long src_addr, dst_addr; @@ -417,7 +520,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( */ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) { up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); return -EINVAL; } @@ -440,24 +543,28 @@ static __always_inline ssize_t mfill_atomic_hugetlb( * retry, dst_vma will be set to NULL and we must lookup again. */ if (!dst_vma) { + dst_vma = uffd_mfill_lock(dst_mm, dst_start, len); + if (IS_ERR(dst_vma)) { + err = PTR_ERR(dst_vma); + goto out; + } + err = -ENOENT; - dst_vma = find_dst_vma(dst_mm, dst_start, len); - if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) - goto out_unlock; + if (!is_vm_hugetlb_page(dst_vma)) + goto out_unlock_vma; err = -EINVAL; if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) - goto out_unlock; + goto out_unlock_vma; - vm_shared = dst_vma->vm_flags & VM_SHARED; - } - - /* - * If not shared, ensure the dst_vma has a anon_vma. - */ - err = -ENOMEM; - if (!vm_shared) { - if (unlikely(anon_vma_prepare(dst_vma))) + /* + * If memory mappings are changing because of non-cooperative + * operation (e.g. mremap) running in parallel, bail out and + * request the user to retry later + */ + down_read(&ctx->map_changing_lock); + err = -EAGAIN; + if (atomic_read(&ctx->mmap_changing)) goto out_unlock; } @@ -502,7 +609,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( if (unlikely(err == -ENOENT)) { up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); BUG_ON(!folio); err = copy_folio_from_user(folio, @@ -511,17 +618,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb( err = -EFAULT; goto out; } - mmap_read_lock(dst_mm); - down_read(&ctx->map_changing_lock); - /* - * If memory mappings are changing because of non-cooperative - * operation (e.g. mremap) running in parallel, bail out and - * request the user to retry later - */ - if (atomic_read(&ctx->mmap_changing)) { - err = -EAGAIN; - break; - } dst_vma = NULL; goto retry; @@ -542,7 +638,8 @@ static __always_inline ssize_t mfill_atomic_hugetlb( out_unlock: up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); +out_unlock_vma: + uffd_mfill_unlock(dst_vma); out: if (folio) folio_put(folio); @@ -634,7 +731,15 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, copied = 0; folio = NULL; retry: - mmap_read_lock(dst_mm); + /* + * Make sure the vma is not shared, that the dst range is + * both valid and fully within a single existing vma. + */ + dst_vma = uffd_mfill_lock(dst_mm, dst_start, len); + if (IS_ERR(dst_vma)) { + err = PTR_ERR(dst_vma); + goto out; + } /* * If memory mappings are changing because of non-cooperative @@ -646,15 +751,6 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, if (atomic_read(&ctx->mmap_changing)) goto out_unlock; - /* - * Make sure the vma is not shared, that the dst range is - * both valid and fully within a single existing vma. - */ - err = -ENOENT; - dst_vma = find_dst_vma(dst_mm, dst_start, len); - if (!dst_vma) - goto out_unlock; - err = -EINVAL; #ifdef CONFIG_USERSWAP if (!uswap_check_copy(dst_vma, flags)) @@ -688,16 +784,6 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) goto out_unlock; - /* - * Ensure the dst_vma has a anon_vma or this page - * would get a NULL anon_vma when moved in the - * dst_vma. - */ - err = -ENOMEM; - if (!(dst_vma->vm_flags & VM_SHARED) && - unlikely(anon_vma_prepare(dst_vma))) - goto out_unlock; - while (src_addr < src_start + len) { pmd_t dst_pmdval; @@ -750,7 +836,7 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, void *kaddr; up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); BUG_ON(!folio); kaddr = kmap_local_folio(folio, 0); @@ -781,7 +867,7 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, out_unlock: up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); out: if (folio) folio_put(folio); -- 2.43.0