Merge patch series "Fix encoding overlayfs fid for fanotify delete events"

Amir Goldstein <amir73il@gmail.com> says:

This is a followup fix to the reported regression [1] that was
introduced by overlayfs non-decodable file handles support in v6.6.

The first fix posted two weeks ago [2] was a quick band aid which is
justified on its own and is still queued on your vfs.fixes branch.

This followup fix fixes the root cause of overlayfs file handle encoding
failure and it also solves a bug with fanotify FAN_DELETE_SELF events on
overlayfs, that was discovered from analysis of the first report.

The fix to fanotify delete events was verified with a new LTP test [3].

[1] https://lore.kernel.org/linux-fsdevel/CAOQ4uxiie81voLZZi2zXS1BziXZCM24nXqPAxbu8kxXCUWdwOg@mail.gmail.com/
[2] https://lore.kernel.org/linux-fsdevel/20241219115301.465396-1-amir73il@gmail.com/
[3] https://github.com/amir73il/ltp/commits/ovl_encode_fid/

* patches from https://lore.kernel.org/r/20250105162404.357058-1-amir73il@gmail.com:
  ovl: support encoding fid from inode with no alias
  ovl: pass realinode to ovl_encode_real_fh() instead of realdentry

Link: https://lore.kernel.org/r/20250105162404.357058-1-amir73il@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

4 files changed, 36 insertions, 30 deletions

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 56eee9f23ea9..0c28e5fa3407 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -415,13 +415,13 @@ int ovl_set_attr(struct ovl_fs *ofs, struct dentry *upperdentry,
 	return err;
 }
 
-struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct dentry *real,
+struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct inode *realinode,
 				  bool is_upper)
 {
 	struct ovl_fh *fh;
 	int fh_type, dwords;
 	int buflen = MAX_HANDLE_SZ;
-	uuid_t *uuid = &real->d_sb->s_uuid;
+	uuid_t *uuid = &realinode->i_sb->s_uuid;
 	int err;
 
 	/* Make sure the real fid stays 32bit aligned */
@@ -438,7 +438,8 @@ struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct dentry *real,
 	 * the price or reconnecting the dentry.
 	 */
 	dwords = buflen >> 2;
-	fh_type = exportfs_encode_fh(real, (void *)fh->fb.fid, &dwords, 0);
+	fh_type = exportfs_encode_inode_fh(realinode, (void *)fh->fb.fid,
+					   &dwords, NULL, 0);
 	buflen = (dwords << 2);
 
 	err = -EIO;
@@ -479,7 +480,7 @@ struct ovl_fh *ovl_get_origin_fh(struct ovl_fs *ofs, struct dentry *origin)
 	if (!ovl_can_decode_fh(origin->d_sb))
 		return NULL;
 
-	return ovl_encode_real_fh(ofs, origin, false);
+	return ovl_encode_real_fh(ofs, d_inode(origin), false);
 }
 
 int ovl_set_origin_fh(struct ovl_fs *ofs, const struct ovl_fh *fh,
@@ -504,7 +505,7 @@ static int ovl_set_upper_fh(struct ovl_fs *ofs, struct dentry *upper,
 	const struct ovl_fh *fh;
 	int err;
 
-	fh = ovl_encode_real_fh(ofs, upper, true);
+	fh = ovl_encode_real_fh(ofs, d_inode(upper), true);
 	if (IS_ERR(fh))
 		return PTR_ERR(fh);
 
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 5868cb222955..444aeeccb6da 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -176,35 +176,37 @@ static int ovl_connect_layer(struct dentry *dentry)
  *
  * Return 0 for upper file handle, > 0 for lower file handle or < 0 on error.
  */
-static int ovl_check_encode_origin(struct dentry *dentry)
+static int ovl_check_encode_origin(struct inode *inode)
 {
-	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+	struct ovl_fs *ofs = OVL_FS(inode->i_sb);
 	bool decodable = ofs->config.nfs_export;
+	struct dentry *dentry;
+	int err;
 
 	/* No upper layer? */
 	if (!ovl_upper_mnt(ofs))
 		return 1;
 
 	/* Lower file handle for non-upper non-decodable */
-	if (!ovl_dentry_upper(dentry) && !decodable)
+	if (!ovl_inode_upper(inode) && !decodable)
 		return 1;
 
 	/* Upper file handle for pure upper */
-	if (!ovl_dentry_lower(dentry))
+	if (!ovl_inode_lower(inode))
 		return 0;
 
 	/*
 	 * Root is never indexed, so if there's an upper layer, encode upper for
 	 * root.
 	 */
-	if (dentry == dentry->d_sb->s_root)
+	if (inode == d_inode(inode->i_sb->s_root))
 		return 0;
 
 	/*
 	 * Upper decodable file handle for non-indexed upper.
 	 */
-	if (ovl_dentry_upper(dentry) && decodable &&
-	    !ovl_test_flag(OVL_INDEX, d_inode(dentry)))
+	if (ovl_inode_upper(inode) && decodable &&
+	    !ovl_test_flag(OVL_INDEX, inode))
 		return 0;
 
 	/*
@@ -213,14 +215,23 @@ static int ovl_check_encode_origin(struct dentry *dentry)
 	 * ovl_connect_layer() will try to make origin's layer "connected" by
 	 * copying up a "connectable" ancestor.
 	 */
-	if (d_is_dir(dentry) && decodable)
-		return ovl_connect_layer(dentry);
+	if (!decodable || !S_ISDIR(inode->i_mode))
+		return 1;
+
+	dentry = d_find_any_alias(inode);
+	if (!dentry)
+		return -ENOENT;
+
+	err = ovl_connect_layer(dentry);
+	dput(dentry);
+	if (err < 0)
+		return err;
 
 	/* Lower file handle for indexed and non-upper dir/non-dir */
 	return 1;
 }
 
-static int ovl_dentry_to_fid(struct ovl_fs *ofs, struct dentry *dentry,
+static int ovl_dentry_to_fid(struct ovl_fs *ofs, struct inode *inode,
 			     u32 *fid, int buflen)
 {
 	struct ovl_fh *fh = NULL;
@@ -231,13 +242,13 @@ static int ovl_dentry_to_fid(struct ovl_fs *ofs, struct dentry *dentry,
 	 * Check if we should encode a lower or upper file handle and maybe
 	 * copy up an ancestor to make lower file handle connectable.
 	 */
-	err = enc_lower = ovl_check_encode_origin(dentry);
+	err = enc_lower = ovl_check_encode_origin(inode);
 	if (enc_lower < 0)
 		goto fail;
 
 	/* Encode an upper or lower file handle */
-	fh = ovl_encode_real_fh(ofs, enc_lower ? ovl_dentry_lower(dentry) :
-				ovl_dentry_upper(dentry), !enc_lower);
+	fh = ovl_encode_real_fh(ofs, enc_lower ? ovl_inode_lower(inode) :
+				ovl_inode_upper(inode), !enc_lower);
 	if (IS_ERR(fh))
 		return PTR_ERR(fh);
 
@@ -251,8 +262,8 @@ out:
 	return err;
 
 fail:
-	pr_warn_ratelimited("failed to encode file handle (%pd2, err=%i)\n",
-			    dentry, err);
+	pr_warn_ratelimited("failed to encode file handle (ino=%lu, err=%i)\n",
+			    inode->i_ino, err);
 	goto out;
 }
 
@@ -260,19 +271,13 @@ static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len,
 			 struct inode *parent)
 {
 	struct ovl_fs *ofs = OVL_FS(inode->i_sb);
-	struct dentry *dentry;
 	int bytes, buflen = *max_len << 2;
 
 	/* TODO: encode connectable file handles */
 	if (parent)
 		return FILEID_INVALID;
 
-	dentry = d_find_any_alias(inode);
-	if (!dentry)
-		return FILEID_INVALID;
-
-	bytes = ovl_dentry_to_fid(ofs, dentry, fid, buflen);
-	dput(dentry);
+	bytes = ovl_dentry_to_fid(ofs, inode, fid, buflen);
 	if (bytes <= 0)
 		return FILEID_INVALID;
 
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 7e27b7d4adee..cea820cb3b55 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -542,7 +542,7 @@ int ovl_verify_origin_xattr(struct ovl_fs *ofs, struct dentry *dentry,
 	struct ovl_fh *fh;
 	int err;
 
-	fh = ovl_encode_real_fh(ofs, real, is_upper);
+	fh = ovl_encode_real_fh(ofs, d_inode(real), is_upper);
 	err = PTR_ERR(fh);
 	if (IS_ERR(fh)) {
 		fh = NULL;
@@ -738,7 +738,7 @@ int ovl_get_index_name(struct ovl_fs *ofs, struct dentry *origin,
 	struct ovl_fh *fh;
 	int err;
 
-	fh = ovl_encode_real_fh(ofs, origin, false);
+	fh = ovl_encode_real_fh(ofs, d_inode(origin), false);
 	if (IS_ERR(fh))
 		return PTR_ERR(fh);
 
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index b361f35762be..0021e2025020 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -865,7 +865,7 @@ int ovl_copy_up_with_data(struct dentry *dentry);
 int ovl_maybe_copy_up(struct dentry *dentry, int flags);
 int ovl_copy_xattr(struct super_block *sb, const struct path *path, struct dentry *new);
 int ovl_set_attr(struct ovl_fs *ofs, struct dentry *upper, struct kstat *stat);
-struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct dentry *real,
+struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct inode *realinode,
 				  bool is_upper);
 struct ovl_fh *ovl_get_origin_fh(struct ovl_fs *ofs, struct dentry *origin);
 int ovl_set_origin_fh(struct ovl_fs *ofs, const struct ovl_fh *fh,