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 --- .../bindings/openrisc/opencores/or1ksim.txt | 39 ++++++++++++++++++++++ 1 file changed, 39 insertions(+) create mode 100644 Documentation/devicetree/bindings/openrisc/opencores/or1ksim.txt (limited to 'Documentation/devicetree/bindings/openrisc') diff --git a/Documentation/devicetree/bindings/openrisc/opencores/or1ksim.txt b/Documentation/devicetree/bindings/openrisc/opencores/or1ksim.txt new file mode 100644 index 000000000..4950c794e --- /dev/null +++ b/Documentation/devicetree/bindings/openrisc/opencores/or1ksim.txt @@ -0,0 +1,39 @@ +OpenRISC Generic SoC +==================== + +Boards and FPGA SoC's which support the OpenRISC standard platform. The +platform essentially follows the conventions of the OpenRISC architecture +specification, however some aspects, such as the boot protocol have been defined +by the Linux port. + +Required properties +------------------- + - compatible: Must include "opencores,or1ksim" + +CPU nodes: +---------- +A "cpus" node is required. Required properties: + - #address-cells: Must be 1. + - #size-cells: Must be 0. +A CPU sub-node is also required for at least CPU 0. Since the topology may +be probed via CPS, it is not necessary to specify secondary CPUs. Required +properties: + - compatible: Must be "opencores,or1200-rtlsvn481". + - reg: CPU number. + - clock-frequency: The CPU clock frequency in Hz. +Example: + cpus { + #address-cells = <1>; + #size-cells = <0>; + cpu@0 { + compatible = "opencores,or1200-rtlsvn481"; + reg = <0>; + clock-frequency = <20000000>; + }; + }; + + +Boot protocol +------------- +The bootloader may pass the following arguments to the kernel: + - r3: address of a flattened device-tree blob or 0x0. -- cgit v1.3.1