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 --- Documentation/ABI/testing/sysfs-bus-css | 56 +++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-bus-css (limited to 'Documentation/ABI/testing/sysfs-bus-css') diff --git a/Documentation/ABI/testing/sysfs-bus-css b/Documentation/ABI/testing/sysfs-bus-css new file mode 100644 index 000000000..d4d5cfb63 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-bus-css @@ -0,0 +1,56 @@ +What: /sys/bus/css/devices/.../type +Date: March 2008 +Contact: linux-s390@vger.kernel.org +Description: Contains the subchannel type, as reported by the hardware. + This attribute is present for all subchannel types. + +What: /sys/bus/css/devices/.../modalias +Date: March 2008 +Contact: linux-s390@vger.kernel.org +Description: Contains the module alias as reported with uevents. + It is of the format css:t and present for all + subchannel types. + +What: /sys/bus/css/drivers/io_subchannel/.../chpids +Date: December 2002 +Contact: linux-s390@vger.kernel.org +Description: Contains the ids of the channel paths used by this + subchannel, as reported by the channel subsystem + during subchannel recognition. + + Note: This is an I/O-subchannel specific attribute. +Users: s390-tools, HAL + +What: /sys/bus/css/drivers/io_subchannel/.../pimpampom +Date: December 2002 +Contact: linux-s390@vger.kernel.org +Description: Contains the PIM/PAM/POM values, as reported by the + channel subsystem when last queried by the common I/O + layer (this implies that this attribute is not necessarily + in sync with the values current in the channel subsystem). + + Note: This is an I/O-subchannel specific attribute. +Users: s390-tools, HAL + +What: /sys/bus/css/devices/.../driver_override +Date: June 2019 +Contact: linux-s390@vger.kernel.org +Description: This file allows the driver for a device to be specified. When + specified, only a driver with a name matching the value written + to driver_override will have an opportunity to bind to the + device. The override is specified by writing a string to the + driver_override file (echo vfio-ccw > driver_override) and + may be cleared with an empty string (echo > driver_override). + This returns the device to standard matching rules binding. + Writing to driver_override does not automatically unbind the + device from its current driver or make any attempt to + automatically load the specified driver. If no driver with a + matching name is currently loaded in the kernel, the device + will not bind to any driver. This also allows devices to + opt-out of driver binding using a driver_override name such as + "none". Only a single driver may be specified in the override, + there is no support for parsing delimiters. + + Note that unlike the mechanism of the same name for pci, this + file does not allow to override basic matching rules. I.e., + the driver must still match the subchannel type of the device. -- cgit v1.3.1