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[ Upstream commit 9899e4d3523faaef17c67141aa80ff2088f17871 ] 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> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.