Bug 43151
| Summary: | hugetlb: use after free bug in "quota" handling | ||
|---|---|---|---|
| Product: | Memory Management | Reporter: | Shachar Raindel (raindel) |
| Component: | Other | Assignee: | Andrew Morton (akpm) |
| Status: | RESOLVED OBSOLETE | ||
| Severity: | high | CC: | alan |
| Priority: | P1 | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Kernel Version: | 2.6.24-3.3+ | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
| Attachments: | Example code - will create an oops on a machine running a debug kernel | ||
Created attachment 73047 [details] Example code - will create an oops on a machine running a debug kernel Description of problem: There is a use after free bug in the kernel hugetlb code. The bug can allow an authenticated, unprivileged local attacker to crash the system (and possibly gain higher privileges) if huge pages are enabled in the system. A fix has been committed to linux-next, commit 90481622d75715bfcb68501280a917dbfe516029 "hugepages: fix use after free bug in "quota" handling" Version-Release number of selected component (if applicable): The bug exists in kernel versions 2.6.24 and above. How reproducible: The attached tarball includes an example code which utilizes a fuse mount with O_DIRECT flag to reproduce the issue. The code will work only on kernels 2.6.32 and above since it uses the new "anonymous mapping" API for getting huge pages. Similar reproduction is possible when using the shmem API or the hugetlbfs API. Stock kernel might not crash, debug kernel will detect the corruption and kill the process. Steps to Reproduce: 1. Untar the attached file 2. Run run_test.sh. The fuse-devel package and sudo rights are required for the fuse mount. Sudo rights are also required for enabling huge pages. 3. Observe the kernel crash when running debug kernel. Normal kernels will (usually) not crash, as the slab allocator will not return the memory blocks to the system general pool for a while. Actual results: An oops is printed, and the requesting process is killed (if using debug kernel). Silent memory corruption happens if debug features are disabled. Expected results: The process should exit without a kernel oops. Additional info: Verified on stock kernel 3.3. Buggy code exists since kernel 2.6.24.