On Mon, May 7, 2018 at 5:54 PM, Wenwen Wang <wang6495@xxxxxxx> wrote: > 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@xxxxxxx> > --- > 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 33261b6..f6179e3 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; > -- > 2.7.4 > Acked-by: Adam Radford <aradford@xxxxxxxxx>
