From: Wenwen Wang <wang6495@umn.edu>
Date: Mon, 7 May 2018 19:54:01 -0500
Subject: [PATCH] scsi: 3w-xxxx: fix a missing-check bug
Git-commit: 9899e4d3523faaef17c67141aa80ff2088f17871
Patch-mainline: v4.18-rc1
References: bsc#1118139

In tw_chrdev_ioctl(), the length of the data buffer is firstly copied
from the userspace pointer 'argp' and saved to the kernel object
'data_buffer_length'. Then a security check is performed on it to make
sure that the length is not more than 'TW_MAX_IOCTL_SECTORS *
512'. Otherwise, an error code -EINVAL is returned. If the security
check is passed, the entire ioctl command is copied again from the
'argp' pointer and saved to the kernel object 'tw_ioctl'. Then, various
operations are performed on 'tw_ioctl' according to the 'cmd'. Given
that the 'argp' pointer resides in userspace, a malicious userspace
process can race to change the buffer length between the two
copies. This way, the user can bypass the security check and inject
invalid data buffer length. This can cause potential security issues in
the following execution.

This patch checks for capable(CAP_SYS_ADMIN) in tw_chrdev_open() to
avoid the above issues.

Signed-off-by: Wenwen Wang <wang6495@umn.edu>
Acked-by: Adam Radford <aradford@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/3w-xxxx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/3w-xxxx.c b/drivers/scsi/3w-xxxx.c
index 33261b690774..f6179e3d6953 100644
--- a/drivers/scsi/3w-xxxx.c
+++ b/drivers/scsi/3w-xxxx.c
@@ -1033,6 +1033,9 @@ static int tw_chrdev_open(struct inode *inode, struct file *file)
 
 	dprintk(KERN_WARNING "3w-xxxx: tw_ioctl_open()\n");
 
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
 	minor_number = iminor(inode);
 	if (minor_number >= tw_device_extension_count)
 		return -ENODEV;
-- 
2.12.3