From: Liam R. Howlett <Liam.Howlett@oracle.com>
Date: Mon, 27 Oct 2025 19:12:54 +0000 (-0400)
Subject: mm/userfaultfd: Move global dst checks to uffd_ctx_lock_and_validate_dst()
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=49ae1f77f6b04bef462ca26c2a3a6cf6f6d7a3c6;p=users%2Fjedix%2Flinux-maple.git

mm/userfaultfd: Move global dst checks to uffd_ctx_lock_and_validate_dst()

Reduce mfill_atomic() further by exporting logic checks to the
lock_and_validate_dst().

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---

diff --git a/mm/shmem.c b/mm/shmem.c
index a08311bebfa3..28c679130f68 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3153,14 +3153,6 @@ static inline struct inode *shmem_get_inode(struct mnt_idmap *idmap,
 static ssize_t shmem_is_dst_valid(struct vm_area_struct *dst_vma,
 		unsigned long dst_start, unsigned long len)
 {
-	/*
-	 * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
-	 * it will overwrite vm_ops, so vma_is_anonymous must return false.
-	 */
-	if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
-	    dst_vma->vm_flags & VM_SHARED))
-		return -EINVAL;
-
 	return 0;
 }
 
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index c64c63a80e0f..ca716bef7a50 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -517,10 +517,13 @@ static inline const struct vm_uffd_ops *vma_get_uffd_ops(struct vm_area_struct *
 	return &default_uffd_ops;
 }
 
+/*
+ * Global checks live here, specific checks are in the callback.
+ */
 static inline ssize_t
 uffd_ctx_lock_and_validate_dst(struct userfaultfd_ctx *ctx,
 		struct vm_area_struct *dst_vma, unsigned long dst_start,
-		unsigned long len)
+		unsigned long len, uffd_flags_t flags)
 {
 	const struct vm_uffd_ops *uffd_ops;
 
@@ -533,6 +536,20 @@ uffd_ctx_lock_and_validate_dst(struct userfaultfd_ctx *ctx,
 	if (atomic_read(&ctx->mmap_changing))
 		return -EAGAIN;
 
+	/*
+	 * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
+	 * it will overwrite vm_ops, so vma_is_anonymous must return false.
+	 */
+	if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
+	    dst_vma->vm_flags & VM_SHARED))
+		return -EINVAL;
+	/*
+	 * validate 'mode' now that we know the dst_vma: don't allow
+	 * a wrprotect copy if the userfaultfd didn't register as WP.
+	 */
+	if ((flags & MFILL_ATOMIC_WP) && !(dst_vma->vm_flags & VM_UFFD_WP))
+		return -EINVAL;
+
 	uffd_ops = vma_get_uffd_ops(dst_vma);
 	WARN_ON_ONCE(!uffd_ops || !uffd_ops->is_dst_valid);
 	return uffd_ops->is_dst_valid(dst_vma, dst_start, len);
@@ -600,7 +617,8 @@ retry:
 			goto out;
 		}
 
-		err = uffd_ctx_lock_and_validate_dst(ctx, dst_vma, dst_start, len);
+		err = uffd_ctx_lock_and_validate_dst(ctx, dst_vma, dst_start,
+						     len, flags);
 		if (err)
 			goto out_unlock;
 	}
@@ -763,26 +781,11 @@ retry:
 		increment = uffd_ops->increment(dst_vma);
 	}
 
-	err = uffd_ctx_lock_and_validate_dst(ctx, dst_vma, dst_start, len);
+	err = uffd_ctx_lock_and_validate_dst(ctx, dst_vma, dst_start, len,
+					     flags);
 	if (err)
 		goto out_unlock;
 
-	err = -EINVAL;
-	/*
-	 * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
-	 * it will overwrite vm_ops, so vma_is_anonymous must return false.
-	 */
-	if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
-	    dst_vma->vm_flags & VM_SHARED))
-		goto out_unlock;
-
-	/*
-	 * validate 'mode' now that we know the dst_vma: don't allow
-	 * a wrprotect copy if the userfaultfd didn't register as WP.
-	 */
-	if ((flags & MFILL_ATOMIC_WP) && !(dst_vma->vm_flags & VM_UFFD_WP))
-		goto out_unlock;
-
 	/*
 	 * If this is a HUGETLB vma, pass off to appropriate routine
 	 */
@@ -790,6 +793,7 @@ retry:
 		return  mfill_atomic_hugetlb(ctx, dst_vma, dst_start,
 					     src_start, len, flags);
 
+	err = -EINVAL;
 	if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
 		goto out_unlock;
 	if (!vma_is_shmem(dst_vma) &&