From 78004e9a87f240df03e2f73120d291763c32e0a7 Mon Sep 17 00:00:00 2001 From: Ali Ahmet Memis Date: Fri, 21 Aug 2026 01:45:27 +0000 Subject: openrisc: fix arbitrary kernel memory access via or1k_atomic syscall sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user pointers, v1 and v2, and swaps the words they point to in hand-written assembly. l.lwz r29,0(r4) l.lwz r27,0(r5) l.sw 0(r4),r27 l.sw 0(r5),r29 The pointers are not checked with access_ok(). The four memory accesses also have no exception table entries. A caller passes a kernel address as either pointer, and the syscall reads from and writes to it directly. This gives an unprivileged process a kernel read/write primitive. It overwrites kernel data such as the sys_call_table, gaining code execution in kernel context. Check both pointers before entering the critical section. Add fixups for the four memory accesses so faults on valid but unmapped user addresses return -EFAULT. [shorne@gmail.com: fix comment style] Fixes: 9d02a4283e9c ("OpenRISC: Boot code") Cc: stable@vger.kernel.org Signed-off-by: Ali Ahmet Memis Signed-off-by: Stafford Horne --- .../admin-guide/namespaces/resource-control.rst | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) create mode 100644 Documentation/admin-guide/namespaces/resource-control.rst (limited to 'Documentation/admin-guide/namespaces/resource-control.rst') diff --git a/Documentation/admin-guide/namespaces/resource-control.rst b/Documentation/admin-guide/namespaces/resource-control.rst new file mode 100644 index 000000000..553a44803 --- /dev/null +++ b/Documentation/admin-guide/namespaces/resource-control.rst @@ -0,0 +1,18 @@ +==================================== +User namespaces and resource control +==================================== + +The kernel contains many kinds of objects that either don't have +individual limits or that have limits which are ineffective when +a set of processes is allowed to switch their UID. On a system +where the admins don't trust their users or their users' programs, +user namespaces expose the system to potential misuse of resources. + +In order to mitigate this, we recommend that admins enable memory +control groups on any system that enables user namespaces. +Furthermore, we recommend that admins configure the memory control +groups to limit the maximum memory usable by any untrusted user. + +Memory control groups can be configured by installing the libcgroup +package present on most distros editing /etc/cgrules.conf, +/etc/cgconfig.conf and setting up libpam-cgroup. -- cgit v1.3.1