[PATCH 04/15] ksmbd: handle empty and disappearing EAs

A zero-length xattr value is valid, but smb2_get_ea() currently treats
every non-positive result from ksmbd_vfs_getxattr() as a missing EA.
Accept zero and encode an empty value in the response.

An xattr can also disappear between listxattr() and getxattr(). Skip an
entry that returns -ENODATA without consuming response space, while
preserving other errors.

Signed-off-by: Ze Tan <[email protected]>
---
 fs/smb/server/smb2pdu.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index 2131625dbc2d..39a72cda6704 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -5245,24 +5245,26 @@ static int smb2_get_ea(struct ksmbd_work *work, struct ksmbd_file *fp,
 			continue;
 
 		ptr = eainfo->name + name_len + 1;
-		buf_free_len -= (offsetof(struct smb2_ea_info, name) +
-				name_len + 1);
-		/* bailout if xattr can't fit in buf_free_len */
 		value_len = ksmbd_vfs_getxattr(idmap, path->dentry,
 					       name, &buf);
-		if (value_len <= 0) {
-			rc = -ENOENT;
+		if (value_len == -ENODATA)
+			continue;
+		if (value_len < 0) {
+			rc = value_len;
 			rsp->hdr.Status = STATUS_INVALID_HANDLE;
 			goto out;
 		}
 
+		buf_free_len -= (offsetof(struct smb2_ea_info, name) +
+				name_len + 1);
 		buf_free_len -= value_len;
 		if (buf_free_len < 0) {
 			kfree(buf);
 			break;
 		}
 
-		memcpy(ptr, buf, value_len);
+		if (value_len)
+			memcpy(ptr, buf, value_len);
 		kfree(buf);
 
 		ptr += value_len;
-- 
2.43.0