From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751888AbdHPFl3 (ORCPT ); Wed, 16 Aug 2017 01:41:29 -0400 Received: from mail-pg0-f45.google.com ([74.125.83.45]:36142 "EHLO mail-pg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751767AbdHPFl0 (ORCPT ); Wed, 16 Aug 2017 01:41:26 -0400 From: Todd Poynor To: Doug Gilbert , "James E.J. Bottomley" , "Martin K. Petersen" Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Hannes Reinecke , Todd Poynor Subject: [PATCH] sg: protect against races between mmap() and SG_SET_RESERVED_SIZE Date: Tue, 15 Aug 2017 22:41:08 -0700 Message-Id: <20170816054108.119890-1-toddpoynor@google.com> X-Mailer: git-send-email 2.14.1.480.gb18f417b89-goog Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Take f_mutex around mmap() processing to protect against races with the SG_SET_RESERVED_SIZE ioctl. Ensure the reserve buffer length remains consistent during the mapping operation, and set the "mmap called" flag to prevent further changes to the reserved buffer size as an atomic operation with the mapping. Signed-off-by: Todd Poynor --- drivers/scsi/sg.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 3a44b4bc872b..a20718e9f1f4 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1233,6 +1233,7 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma) unsigned long req_sz, len, sa; Sg_scatter_hold *rsv_schp; int k, length; + int ret = 0; if ((!filp) || (!vma) || (!(sfp = (Sg_fd *) filp->private_data))) return -ENXIO; @@ -1243,8 +1244,11 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma) if (vma->vm_pgoff) return -EINVAL; /* want no offset */ rsv_schp = &sfp->reserve; - if (req_sz > rsv_schp->bufflen) - return -ENOMEM; /* cannot map more than reserved buffer */ + mutex_lock(&sfp->f_mutex); + if (req_sz > rsv_schp->bufflen) { + ret = -ENOMEM; /* cannot map more than reserved buffer */ + goto out; + } sa = vma->vm_start; length = 1 << (PAGE_SHIFT + rsv_schp->page_order); @@ -1258,7 +1262,9 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma) vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP; vma->vm_private_data = sfp; vma->vm_ops = &sg_mmap_vm_ops; - return 0; +out: + mutex_unlock(&sfp->f_mutex); + return ret; } static void -- 2.14.1.480.gb18f417b89-goog