From: Jeremy Allison <jra@samba.org>
Date: Mon, 14 Dec 2020 20:07:48 +0000 (-0800)
Subject: smbd: smb_info_set_ea() can only get fsp==NULL in POSIX mode accessing a symlink.
X-Git-Tag: samba-4.14.0rc1~258
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0049a34b27f385ef18d4c84c993d1364d4dbbb0f;p=thirdparty%2Fsamba.git

smbd: smb_info_set_ea() can only get fsp==NULL in POSIX mode accessing a symlink.

Ensure this is the case and force-return NT_STATUS_ACCESS_DENIED here.
Remove any race condition if anyone modifies the symlink whilst the
operation is in process.

This now allows us to require a valid fsp for operations on EAs.

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
---

diff --git a/source3/smbd/trans2.c b/source3/smbd/trans2.c
index 6b856424c62..da1614f7b1d 100644
--- a/source3/smbd/trans2.c
+++ b/source3/smbd/trans2.c
@@ -6820,6 +6820,27 @@ static NTSTATUS smb_info_set_ea(connection_struct *conn,
 		return NT_STATUS_INVALID_PARAMETER;
 	}
 
+	if (fsp == NULL) {
+		/*
+		 * The only way fsp can be NULL here is if
+		 * smb_fname points at a symlink and
+		 * and we're in POSIX context.
+		 * Ensure this is the case.
+		 *
+		 * There is still a race condition in that
+		 * the symlink could be changed after we
+		 * checked it, so ensure we only operate
+		 * EA setting on a file handle.
+		 */
+		SMB_ASSERT(smb_fname->flags & SMB_FILENAME_POSIX_PATH);
+		if (!(smb_fname->flags & SMB_FILENAME_POSIX_PATH)) {
+			return NT_STATUS_ACCESS_DENIED;
+		}
+		status = refuse_symlink(conn, NULL, smb_fname);
+		SMB_ASSERT(NT_STATUS_EQUAL(status, NT_STATUS_ACCESS_DENIED));
+		return NT_STATUS_ACCESS_DENIED;
+	}
+
 	status = set_ea(conn, fsp, smb_fname, ea_list);
 
 	return status;