Linux Kernel Refcount Reference Count Overflow Vulnerability [CVE-2019-11487]
CVE Number – CVE-2019-11487
A vulnerability in the Linux Kernel could allow a local attacker to cause a denial of service (DoS) condition on a targeted system.
The vulnerability is related to the fs/fuse/dev.c, fs/pipe.c, fs/splice.c, include/linux/mm.h, include/linux/pipe_fs_i.h, kernel/trace/trace.c, mm/gup.c, and mm/hugetlb.c source code files of the affected software, and is due to a page->_refcount reference count overflow condition that could occur when a FUSE request is made on an affected system with about 140 GB of RAM. An attacker could exploit the vulnerability by accessing the system and executing an application that submits a FUSE request to the affected software. A successful exploit could trigger a page->_refcountreference count overflow condition that causes the software to crash, resulting in a DoS condition.Proof-of-concept (PoC) code that demonstrates an exploit of this vulnerability is publicly available.Kernel.org has confirmed the vulnerability and released software updates.
Analysis
- To exploit this vulnerability, the attacker must have user-level access to the targeted system. This access requirement could reduce the likelihood of a successful exploit.
Safeguards
- Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to access local systems.
Administrators are advised to allow only privileged users to access administration or management systems.
Administrators are advised to monitor critical systems.
Vendor Announcements
- Kernel.org has released git commits at the following links:
15fab63e1e57be9fdb5eec1bbc5916e9825e9acb
6b3a707736301c2128ca85ce85fb13f60b5e350a
88b1a17dfc3ed7728316478fae0f5ad508f50397
8fde12ca79aff9b5ba951fce1a2641901b8d8e64
f958d7b528b1b40c44cfda5eabe2d82760d868c3
Fixed Software
- Kernel.org has released software updates at the following links:
fs: prevent page refcount overflow in pipe_buf_get
Merge branch ‘page-refs’ (page ref overflow)
mm: add ‘try_get_page()’ helper function
mm: prevent get_user_pages() from overflowing page refcount
mm: make page ref count overflow check tighter and more explicit
Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.