smb3: fix default permissions on new files when mounting with modefromsid

When mounting with "modefromsid" mount parm most servers will require
that some default permissions are given to users in the ACL on newly
created files, files created with the new 'sd context' - when passing in
an sd context on create, permissions are not inherited from the parent
directory, so in addition to the ACE with the special SID which contains
the mode, we also must pass in an ACE allowing users to access the file
(GENERIC_ALL for authenticated users seemed like a reasonable default,
although later we could allow a mount option or config switch to make
it GENERIC_ALL for EVERYONE special sid).

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-By: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

fs/cifs/cifsacl.c

@@ -802,6 +802,26 @@ static void parse_dacl(struct cifs_acl *pdacl, char *end_of_acl,
 	return;
 }
 
+unsigned int setup_authusers_ACE(struct cifs_ace *pntace)
+{
+	int i;
+	unsigned int ace_size = 20;
+
+	pntace->type = ACCESS_ALLOWED_ACE_TYPE;
+	pntace->flags = 0x0;
+	pntace->access_req = cpu_to_le32(GENERIC_ALL);
+	pntace->sid.num_subauth = 1;
+	pntace->sid.revision = 1;
+	for (i = 0; i < NUM_AUTHS; i++)
+		pntace->sid.authority[i] =  sid_authusers.authority[i];
+
+	pntace->sid.sub_auth[0] =  sid_authusers.sub_auth[0];
+
+	/* size = 1 + 1 + 2 + 4 + 1 + 1 + 6 + (psid->num_subauth*4) */
+	pntace->size = cpu_to_le16(ace_size);
+	return ace_size;
+}
+
 /*
  * Fill in the special SID based on the mode. See
  * http://technet.microsoft.com/en-us/library/hh509017(v=ws.10).aspx

fs/cifs/cifsproto.h

@@ -213,6 +213,7 @@ extern struct cifs_ntsd *get_cifs_acl_by_fid(struct cifs_sb_info *,
 						const struct cifs_fid *, u32 *);
 extern int set_cifs_acl(struct cifs_ntsd *, __u32, struct inode *,
 				const char *, int);
+extern unsigned int setup_authusers_ACE(struct cifs_ace *pace);
 extern unsigned int setup_special_mode_ACE(struct cifs_ace *pace, __u64 nmode);
 
 extern void dequeue_mid(struct mid_q_entry *mid, bool malformed);

fs/cifs/smb2pdu.c

@@ -2199,13 +2199,14 @@ create_sd_buf(umode_t mode, unsigned int *len)
 	struct cifs_ace *pace;
 	unsigned int sdlen, acelen;
 
-	*len = roundup(sizeof(struct crt_sd_ctxt) + sizeof(struct cifs_ace), 8);
+	*len = roundup(sizeof(struct crt_sd_ctxt) + sizeof(struct cifs_ace) * 2,
+			8);
 	buf = kzalloc(*len, GFP_KERNEL);
 	if (buf == NULL)
 		return buf;
 
 	sdlen = sizeof(struct smb3_sd) + sizeof(struct smb3_acl) +
-		 sizeof(struct cifs_ace);
+		 2 * sizeof(struct cifs_ace);
 
 	buf->ccontext.DataOffset = cpu_to_le16(offsetof
 					(struct crt_sd_ctxt, sd));
@@ -2232,8 +2233,12 @@ create_sd_buf(umode_t mode, unsigned int *len)
 	/* create one ACE to hold the mode embedded in reserved special SID */
 	pace = (struct cifs_ace *)(sizeof(struct crt_sd_ctxt) + (char *)buf);
 	acelen = setup_special_mode_ACE(pace, (__u64)mode);
+	/* and one more ACE to allow access for authenticated users */
+	pace = (struct cifs_ace *)(acelen + (sizeof(struct crt_sd_ctxt) +
+		(char *)buf));
+	acelen += setup_authusers_ACE(pace);
 	buf->acl.AclSize = cpu_to_le16(sizeof(struct cifs_acl) + acelen);
-	buf->acl.AceCount = cpu_to_le16(1);
+	buf->acl.AceCount = cpu_to_le16(2);
 	return buf;
 }