afs: Fix double-unmap of directory block

Fix afs_edit_dir_remove() to use a cleanup function to unmap the block
pointed to by afs_dir_iter::block if it's left pointing to something rather
than manually kunmapping the blocks.  Manually kunmapping without clearing
iter.blocks can result in a double-kunmap if afs_dir_find_block() is called
twice in a row (which would be the case if the block being modified is not
first in the hash chain).

Fixes: a5b5beebcf96 ("afs: Use the contained hashtable to search a directory")
Closes: https://sashiko.dev/#/patchset/20260716103030.3065561-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
cc: stable@vger.kernel.org

fs/afs/dir_edit.c

diff --git a/fs/afs/dir_edit.c b/fs/afs/dir_edit.c
index 3ead36a..c313030 100644
--- a/fs/afs/dir_edit.c
+++ b/fs/afs/dir_edit.c
@@ -442,7 +442,7 @@ void afs_edit_dir_remove(struct afs_vnode *vnode,
 	/* Check and clear the entry. */
 	de = &block->dirents[slot];
 	if (de->u.valid != 1)
-		goto error_unmap;
+		goto error;
 
 	trace_afs_edit_dir(vnode, why, afs_edit_dir_delete, b, slot,
 			   ntohl(de->u.vnode), ntohl(de->u.unique),
@@ -458,7 +458,6 @@ void afs_edit_dir_remove(struct afs_vnode *vnode,
 	/* Clear the constituent entries. */
 	next = de->u.hash_next;
 	memset(de, 0, sizeof(*de) * iter.nr_slots);
-	kunmap_local(block);
 
 	/* Adjust the hash chain: if iter->prev_entry is 0, the hashtable head
 	 * index is previous; otherwise it's slot number of the previous entry.
@@ -485,7 +484,6 @@ void afs_edit_dir_remove(struct afs_vnode *vnode,
 		pde = &pblock->dirents[ps];
 		prev_next = pde->u.hash_next;
 		if (prev_next != htons(entry)) {
-			kunmap_local(pblock);
 			pr_warn("%llx:%llx:%x: not prev in chain b=%x p=%x,%x e=%x %*s",
 				vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique,
 				iter.bucket, iter.prev_entry, prev_next, entry,
@@ -493,7 +491,6 @@ void afs_edit_dir_remove(struct afs_vnode *vnode,
 			goto error;
 		}
 		pde->u.hash_next = next;
-		kunmap_local(pblock);
 	}
 
 	netfs_single_mark_inode_dirty(&vnode->netfs.inode);
@@ -503,18 +500,16 @@ void afs_edit_dir_remove(struct afs_vnode *vnode,
 	_debug("Remove %s from %u[%u]", name->name, b, slot);
 
 out_unmap:
+	afs_dir_end_iter(&iter);
 	kunmap_local(meta);
 	_leave("");
 	return;
 
 already_invalidated:
-	kunmap_local(block);
 	trace_afs_edit_dir(vnode, why, afs_edit_dir_delete_inval,
 			   0, 0, 0, 0, name->name);
 	goto out_unmap;
 
-error_unmap:
-	kunmap_local(block);
 error:
 	trace_afs_edit_dir(vnode, why, afs_edit_dir_delete_error,
 			   0, 0, 0, 0, name->name);

fs/afs/dir_search.c

diff --git a/fs/afs/dir_search.c b/fs/afs/dir_search.c
index 4977ad8..11ebdff 100644
--- a/fs/afs/dir_search.c
+++ b/fs/afs/dir_search.c
@@ -75,10 +75,7 @@ union afs_xdr_dir_block *afs_dir_find_block(struct afs_dir_iter *iter, size_t bl
 
 	_enter("%zx,%d", block, slot);
 
-	if (iter->block) {
-		kunmap_local(iter->block);
-		iter->block = NULL;
-	}
+	afs_dir_end_iter(iter);
 
 	if (dvnode->directory_size < blend)
 		goto fail;
@@ -174,10 +171,7 @@ int afs_dir_search_bucket(struct afs_dir_iter *iter, const struct qstr *name,
 	ret = -ENOENT;
 found:
 bad:
-	if (iter->block) {
-		kunmap_local(iter->block);
-		iter->block = NULL;
-	}
+	afs_dir_end_iter(iter);
 	if (ret == -ESTALE)
 		afs_invalidate_dir(iter->dvnode, afs_dir_invalid_iter_stale);
 	_leave(" = %d", ret);

fs/afs/internal.h

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 290873b..330654e 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -1133,6 +1133,14 @@ int afs_dir_search_bucket(struct afs_dir_iter *iter, const struct qstr *name,
 int afs_dir_search(struct afs_vnode *dvnode, const struct qstr *name,
 		   struct afs_fid *_fid, afs_dataversion_t *_dir_version);
 
+static inline void afs_dir_end_iter(struct afs_dir_iter *iter)
+{
+	if (iter->block) {
+		kunmap_local(iter->block);
+		iter->block = NULL;
+	}
+}
+
 /*
  * dir_silly.c
  */