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 upstream, 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: A general protection fault message is printed, and the server is frozen. Expected results: The process should exit without the kernel crashing. Additional info: Verified on RHEL 6.0 with Dell PowerEdge 2950, should exist also on RHEL 6.2 and 6.1. Upstream commit: http://git.kernel.org/linus/90481622d75715bfcb68501280a917dbfe516029 Acknowledgements: Red Hat would like to thank Shachar Raindel for reporting this issue.
*** Bug 815065 has been marked as a duplicate of this bug. ***
Statement: This issue did not affect the versions of the Linux kernel as shipped with Red Hat Enterprise Linux 5. Future kernel updates for Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux MRG 2 may address this issue.
Created kernel tracking bugs for this issue Affects: fedora-all [bug 843038]
(In reply to comment #0) > 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 upstream, 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. Hi Eugene. The proposed testcase seem to be missing in attachment.
(In reply to comment #7) > Hi Eugene. > > The proposed testcase seem to be missing in attachment. Please see bug 815065 comment #0
This issue has been addressed in following products: Red Hat Enterprise Linux 6 Via RHSA-2012:1426 https://rhn.redhat.com/errata/RHSA-2012-1426.html
This issue has been addressed in following products: MRG for RHEL-6 v.2 Via RHSA-2012:1491 https://rhn.redhat.com/errata/RHSA-2012-1491.html
This issue has been addressed in following products: Red Hat Enterprise Linux 6.2 EUS - Server Only Via RHSA-2013:0741 https://rhn.redhat.com/errata/RHSA-2013-0741.html