Merge tag 'vfs-6.19-rc1.ovl' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull overlayfs cred guard conversion from Christian Brauner:
 "This converts all of overlayfs to use credential guards, eliminating
  manual credential management throughout the filesystem.

  Credential guard conversion:

   - Convert all of overlayfs to use credential guards, replacing the
     manual ovl_override_creds()/ovl_revert_creds() pattern with scoped
     guards.

     This makes credential handling visually explicit and eliminates a
     class of potential bugs from mismatched override/revert calls.

     (1) Basic credential guard (with_ovl_creds)
     (2) Creator credential guard (ovl_override_creator_creds):

         Introduced a specialized guard for file creation operations
         that handles the two-phase credential override (mounter
         credentials, then fs{g,u}id override). The new pattern is much
         clearer:

         with_ovl_creds(dentry->d_sb) {
                 scoped_class(prepare_creds_ovl, cred, dentry, inode, mode) {
                         if (IS_ERR(cred))
                                 return PTR_ERR(cred);
                         /* creation operations */
                 }
         }

     (3) Copy-up credential guard (ovl_cu_creds):

         Introduced a specialized guard for copy-up operations,
         simplifying the previous struct ovl_cu_creds helper and
         associated functions.

         Ported ovl_copy_up_workdir() and ovl_copy_up_tmpfile() to this
         pattern.

  Cleanups:

   - Remove ovl_revert_creds() after all callers converted to guards

   - Remove struct ovl_cu_creds and associated functions

   - Drop ovl_setup_cred_for_create() after conversion

   - Refactor ovl_fill_super(), ovl_lookup(), ovl_iterate(),
     ovl_rename() for cleaner credential guard scope

   - Introduce struct ovl_renamedata to simplify rename handling

   - Don't override credentials for ovl_check_whiteouts() (unnecessary)

   - Remove unneeded semicolon"

* tag 'vfs-6.19-rc1.ovl' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (54 commits)
  ovl: remove unneeded semicolon
  ovl: remove struct ovl_cu_creds and associated functions
  ovl: port ovl_copy_up_tmpfile() to cred guard
  ovl: mark *_cu_creds() as unused temporarily
  ovl: port ovl_copy_up_workdir() to cred guard
  ovl: add copy up credential guard
  ovl: drop ovl_setup_cred_for_create()
  ovl: port ovl_create_or_link() to new ovl_override_creator_creds cleanup guard
  ovl: mark ovl_setup_cred_for_create() as unused temporarily
  ovl: reflow ovl_create_or_link()
  ovl: port ovl_create_tmpfile() to new ovl_override_creator_creds cleanup guard
  ovl: add ovl_override_creator_creds cred guard
  ovl: remove ovl_revert_creds()
  ovl: port ovl_fill_super() to cred guard
  ovl: refactor ovl_fill_super()
  ovl: port ovl_lower_positive() to cred guard
  ovl: port ovl_lookup() to cred guard
  ovl: refactor ovl_lookup()
  ovl: port ovl_copyfile() to cred guard
  ovl: port ovl_rename() to cred guard
  ...

1 files changed, 49 insertions, 69 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 1af700668089..bdbf86b56a9b 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -25,7 +25,6 @@ int ovl_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	bool full_copy_up = false;
 	struct dentry *upperdentry;
-	const struct cred *old_cred;
 
 	err = setattr_prepare(&nop_mnt_idmap, dentry, attr);
 	if (err)
@@ -78,9 +77,8 @@ int ovl_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 			goto out_put_write;
 
 		inode_lock(upperdentry->d_inode);
-		old_cred = ovl_override_creds(dentry->d_sb);
-		err = ovl_do_notify_change(ofs, upperdentry, attr);
-		ovl_revert_creds(old_cred);
+		with_ovl_creds(dentry->d_sb)
+			err = ovl_do_notify_change(ofs, upperdentry, attr);
 		if (!err)
 			ovl_copyattr(dentry->d_inode);
 		inode_unlock(upperdentry->d_inode);
@@ -153,13 +151,22 @@ static void ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
 	}
 }
 
+static inline int ovl_real_getattr_nosec(struct super_block *sb,
+					 const struct path *path,
+					 struct kstat *stat, u32 request_mask,
+					 unsigned int flags)
+{
+	with_ovl_creds(sb)
+		return vfs_getattr_nosec(path, stat, request_mask, flags);
+}
+
 int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
 		struct kstat *stat, u32 request_mask, unsigned int flags)
 {
 	struct dentry *dentry = path->dentry;
+	struct super_block *sb = dentry->d_sb;
 	enum ovl_path_type type;
 	struct path realpath;
-	const struct cred *old_cred;
 	struct inode *inode = d_inode(dentry);
 	bool is_dir = S_ISDIR(inode->i_mode);
 	int fsid = 0;
@@ -169,10 +176,9 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
 	metacopy_blocks = ovl_is_metacopy_dentry(dentry);
 
 	type = ovl_path_real(dentry, &realpath);
-	old_cred = ovl_override_creds(dentry->d_sb);
-	err = vfs_getattr_nosec(&realpath, stat, request_mask, flags);
+	err = ovl_real_getattr_nosec(sb, &realpath, stat, request_mask, flags);
 	if (err)
-		goto out;
+		return err;
 
 	/* Report the effective immutable/append-only STATX flags */
 	generic_fill_statx_attr(inode, stat);
@@ -195,10 +201,9 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
 					(!is_dir ? STATX_NLINK : 0);
 
 			ovl_path_lower(dentry, &realpath);
-			err = vfs_getattr_nosec(&realpath, &lowerstat, lowermask,
-						flags);
+			err = ovl_real_getattr_nosec(sb, &realpath, &lowerstat, lowermask, flags);
 			if (err)
-				goto out;
+				return err;
 
 			/*
 			 * Lower hardlinks may be broken on copy up to different
@@ -248,10 +253,10 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
 
 			ovl_path_lowerdata(dentry, &realpath);
 			if (realpath.dentry) {
-				err = vfs_getattr_nosec(&realpath, &lowerdatastat,
-							lowermask, flags);
+				err = ovl_real_getattr_nosec(sb, &realpath, &lowerdatastat,
+							     lowermask, flags);
 				if (err)
-					goto out;
+					return err;
 			} else {
 				lowerdatastat.blocks =
 					round_up(stat->size, stat->blksize) >> 9;
@@ -279,9 +284,6 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
 	if (!is_dir && ovl_test_flag(OVL_INDEX, d_inode(dentry)))
 		stat->nlink = dentry->d_inode->i_nlink;
 
-out:
-	ovl_revert_creds(old_cred);
-
 	return err;
 }
 
@@ -291,7 +293,6 @@ int ovl_permission(struct mnt_idmap *idmap,
 	struct inode *upperinode = ovl_inode_upper(inode);
 	struct inode *realinode;
 	struct path realpath;
-	const struct cred *old_cred;
 	int err;
 
 	/* Careful in RCU walk mode */
@@ -309,33 +310,26 @@ int ovl_permission(struct mnt_idmap *idmap,
 	if (err)
 		return err;
 
-	old_cred = ovl_override_creds(inode->i_sb);
 	if (!upperinode &&
 	    !special_file(realinode->i_mode) && mask & MAY_WRITE) {
 		mask &= ~(MAY_WRITE | MAY_APPEND);
 		/* Make sure mounter can read file for copy up later */
 		mask |= MAY_READ;
 	}
-	err = inode_permission(mnt_idmap(realpath.mnt), realinode, mask);
-	ovl_revert_creds(old_cred);
 
-	return err;
+	with_ovl_creds(inode->i_sb)
+		return inode_permission(mnt_idmap(realpath.mnt), realinode, mask);
 }
 
 static const char *ovl_get_link(struct dentry *dentry,
 				struct inode *inode,
 				struct delayed_call *done)
 {
-	const struct cred *old_cred;
-	const char *p;
-
 	if (!dentry)
 		return ERR_PTR(-ECHILD);
 
-	old_cred = ovl_override_creds(dentry->d_sb);
-	p = vfs_get_link(ovl_dentry_real(dentry), done);
-	ovl_revert_creds(old_cred);
-	return p;
+	with_ovl_creds(dentry->d_sb)
+		return vfs_get_link(ovl_dentry_real(dentry), done);
 }
 
 #ifdef CONFIG_FS_POSIX_ACL
@@ -465,11 +459,8 @@ struct posix_acl *do_ovl_get_acl(struct mnt_idmap *idmap,
 
 		acl = get_cached_acl_rcu(realinode, type);
 	} else {
-		const struct cred *old_cred;
-
-		old_cred = ovl_override_creds(inode->i_sb);
-		acl = ovl_get_acl_path(&realpath, posix_acl_xattr_name(type), noperm);
-		ovl_revert_creds(old_cred);
+		with_ovl_creds(inode->i_sb)
+			acl = ovl_get_acl_path(&realpath, posix_acl_xattr_name(type), noperm);
 	}
 
 	return acl;
@@ -481,7 +472,6 @@ static int ovl_set_or_remove_acl(struct dentry *dentry, struct inode *inode,
 	int err;
 	struct path realpath;
 	const char *acl_name;
-	const struct cred *old_cred;
 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	struct dentry *upperdentry = ovl_dentry_upper(dentry);
 	struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
@@ -495,10 +485,8 @@ static int ovl_set_or_remove_acl(struct dentry *dentry, struct inode *inode,
 		struct posix_acl *real_acl;
 
 		ovl_path_lower(dentry, &realpath);
-		old_cred = ovl_override_creds(dentry->d_sb);
-		real_acl = vfs_get_acl(mnt_idmap(realpath.mnt), realdentry,
-				       acl_name);
-		ovl_revert_creds(old_cred);
+		with_ovl_creds(dentry->d_sb)
+			real_acl = vfs_get_acl(mnt_idmap(realpath.mnt), realdentry, acl_name);
 		if (IS_ERR(real_acl)) {
 			err = PTR_ERR(real_acl);
 			goto out;
@@ -518,12 +506,12 @@ static int ovl_set_or_remove_acl(struct dentry *dentry, struct inode *inode,
 	if (err)
 		goto out;
 
-	old_cred = ovl_override_creds(dentry->d_sb);
-	if (acl)
-		err = ovl_do_set_acl(ofs, realdentry, acl_name, acl);
-	else
-		err = ovl_do_remove_acl(ofs, realdentry, acl_name);
-	ovl_revert_creds(old_cred);
+	with_ovl_creds(dentry->d_sb) {
+		if (acl)
+			err = ovl_do_set_acl(ofs, realdentry, acl_name, acl);
+		else
+			err = ovl_do_remove_acl(ofs, realdentry, acl_name);
+	}
 	ovl_drop_write(dentry);
 
 	/* copy c/mtime */
@@ -588,9 +576,7 @@ int ovl_update_time(struct inode *inode, int flags)
 static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		      u64 start, u64 len)
 {
-	int err;
 	struct inode *realinode = ovl_inode_realdata(inode);
-	const struct cred *old_cred;
 
 	if (!realinode)
 		return -EIO;
@@ -598,11 +584,8 @@ static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 	if (!realinode->i_op->fiemap)
 		return -EOPNOTSUPP;
 
-	old_cred = ovl_override_creds(inode->i_sb);
-	err = realinode->i_op->fiemap(realinode, fieinfo, start, len);
-	ovl_revert_creds(old_cred);
-
-	return err;
+	with_ovl_creds(inode->i_sb)
+		return realinode->i_op->fiemap(realinode, fieinfo, start, len);
 }
 
 /*
@@ -653,7 +636,6 @@ int ovl_fileattr_set(struct mnt_idmap *idmap,
 {
 	struct inode *inode = d_inode(dentry);
 	struct path upperpath;
-	const struct cred *old_cred;
 	unsigned int flags;
 	int err;
 
@@ -665,18 +647,18 @@ int ovl_fileattr_set(struct mnt_idmap *idmap,
 		if (err)
 			goto out;
 
-		old_cred = ovl_override_creds(inode->i_sb);
-		/*
-		 * Store immutable/append-only flags in xattr and clear them
-		 * in upper fileattr (in case they were set by older kernel)
-		 * so children of "ovl-immutable" directories lower aliases of
-		 * "ovl-immutable" hardlinks could be copied up.
-		 * Clear xattr when flags are cleared.
-		 */
-		err = ovl_set_protattr(inode, upperpath.dentry, fa);
-		if (!err)
-			err = ovl_real_fileattr_set(&upperpath, fa);
-		ovl_revert_creds(old_cred);
+		with_ovl_creds(inode->i_sb) {
+			/*
+			 * Store immutable/append-only flags in xattr and clear them
+			 * in upper fileattr (in case they were set by older kernel)
+			 * so children of "ovl-immutable" directories lower aliases of
+			 * "ovl-immutable" hardlinks could be copied up.
+			 * Clear xattr when flags are cleared.
+			 */
+			err = ovl_set_protattr(inode, upperpath.dentry, fa);
+			if (!err)
+				err = ovl_real_fileattr_set(&upperpath, fa);
+		}
 		ovl_drop_write(dentry);
 
 		/*
@@ -730,15 +712,13 @@ int ovl_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
 {
 	struct inode *inode = d_inode(dentry);
 	struct path realpath;
-	const struct cred *old_cred;
 	int err;
 
 	ovl_path_real(dentry, &realpath);
 
-	old_cred = ovl_override_creds(inode->i_sb);
-	err = ovl_real_fileattr_get(&realpath, fa);
+	with_ovl_creds(inode->i_sb)
+		err = ovl_real_fileattr_get(&realpath, fa);
 	ovl_fileattr_prot_flags(inode, fa);
-	ovl_revert_creds(old_cred);
 
 	return err;
 }