cifs: Fix access_flags_to_smbopen_mode

When converting access_flags to SMBOPEN mode, check for all possible access
flags, not only GENERIC_READ and GENERIC_WRITE flags.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: pali

fs/smb/client/cifssmb.c

@@ -1041,15 +1041,31 @@ static __u16 convert_disposition(int disposition)
 static int
 access_flags_to_smbopen_mode(const int access_flags)
 {
-	int masked_flags = access_flags & (GENERIC_READ | GENERIC_WRITE);
-
-	if (masked_flags == GENERIC_READ)
-		return SMBOPEN_READ;
-	else if (masked_flags == GENERIC_WRITE)
+	/*
+	 * SYSTEM_SECURITY grants both read and write access to SACL, treat is as read/write.
+	 * MAXIMUM_ALLOWED grants as many access as possible, so treat it as read/write too.
+	 * SYNCHRONIZE as is does not grant any specific access, so do not check its mask.
+	 * If only SYNCHRONIZE bit is specified then fallback to read access.
+	 */
+	bool with_write_flags = access_flags & (FILE_WRITE_DATA | FILE_APPEND_DATA | FILE_WRITE_EA |
+						FILE_DELETE_CHILD | FILE_WRITE_ATTRIBUTES | DELETE |
+						WRITE_DAC | WRITE_OWNER | SYSTEM_SECURITY |
+						MAXIMUM_ALLOWED | GENERIC_WRITE | GENERIC_ALL);
+	bool with_read_flags = access_flags & (FILE_READ_DATA | FILE_READ_EA | FILE_EXECUTE |
+						FILE_READ_ATTRIBUTES | READ_CONTROL |
+						SYSTEM_SECURITY | MAXIMUM_ALLOWED | GENERIC_ALL |
+						GENERIC_EXECUTE | GENERIC_READ);
+	bool with_execute_flags = access_flags & (FILE_EXECUTE | MAXIMUM_ALLOWED | GENERIC_ALL |
+						GENERIC_EXECUTE);
+
+	if (with_write_flags && with_read_flags)
+		return SMBOPEN_READWRITE;
+	else if (with_write_flags)
 		return SMBOPEN_WRITE;
-
-	/* just go for read/write */
-	return SMBOPEN_READWRITE;
+	else if (with_execute_flags)
+		return SMBOPEN_EXECUTE;
+	else
+		return SMBOPEN_READ;
 }
 
 int