From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:60290 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726883AbeKTQEL (ORCPT ); Tue, 20 Nov 2018 11:04:11 -0500 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wAK5YjOx031771 for ; Tue, 20 Nov 2018 00:36:54 -0500 Received: from e13.ny.us.ibm.com (e13.ny.us.ibm.com [129.33.205.203]) by mx0a-001b2d01.pphosted.com with ESMTP id 2nvavctttm-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 20 Nov 2018 00:36:54 -0500 Received: from localhost by e13.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 20 Nov 2018 05:36:52 -0000 From: Chandan Rajendra To: linux-fsdevel@vger.kernel.org Cc: Chandan Rajendra , viro@zeniv.linux.org.uk, joe@perches.com, abdhalee@linux.vnet.ibm.com Subject: [PATCH RESEND] get_fs_type: Validate fs type string argument Date: Tue, 20 Nov 2018 11:06:42 +0530 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <20181120053642.24513-1-chandan@linux.vnet.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On ppc64le, When a string with PAGE_SIZE - 1 (i.e. 64k-1) length is passed as a "filesystem type" argument to the mount(2) syscall, copy_mount_string() ends up allocating 64k (the PAGE_SIZE on ppc64le) worth of space for holding the string in kernel's address space. Later, in set_precision() (invoked by get_fs_type() -> __request_module() -> vsnprintf()), we end up assigning strlen(fs-type-string) i.e. 65535 as the value to 'struct printf_spec'->precision member. This field has a width of 16 bits and it is a signed data type. Hence an invalid value ends up getting assigned. This causes the "WARN_ONCE(spec->precision != prec, "precision %d too large", prec)" statement inside set_precision() to be executed. This commit fixes the bug by validating the length of the "filesystem type" argument passed to get_fs_type() function. Signed-off-by: Chandan Rajendra Reported-by: Abdul Haleem Suggested-by: Joe Perches --- fs/filesystems.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/filesystems.c b/fs/filesystems.c index 9135646e41ac..a61caf5b6ad3 100644 --- a/fs/filesystems.c +++ b/fs/filesystems.c @@ -268,6 +268,9 @@ struct file_system_type *get_fs_type(const char *name) const char *dot = strchr(name, '.'); int len = dot ? dot - name : strlen(name); + if (len >= PATH_MAX) + return NULL; + fs = __get_fs_type(name, len); if (!fs && (request_module("fs-%.*s", len, name) == 0)) { fs = __get_fs_type(name, len); -- 2.19.1