openrisc: fix arbitrary kernel memory access via or1k_atomic syscall

Overview

In the Linux kernel, the following vulnerability has been resolved:

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.

[[email protected]: fix comment style]

Affected

• Linux >= 9d02a4283e9ce4e9ca11ff00615bdacdb0515a1a < bf310718c6fa6adeee06d207a55489546d860e2c
• Linux >= 9d02a4283e9ce4e9ca11ff00615bdacdb0515a1a < 497cba0b02e5555d99fe9ee1dc478af743ab7f7a
• Linux >= 9d02a4283e9ce4e9ca11ff00615bdacdb0515a1a < 1f2e92e499d863f81df1732af59b4a3559969193
• Linux >= 9d02a4283e9ce4e9ca11ff00615bdacdb0515a1a < 574ae2ac2b314aa33498cd2c28add106cbe644f2
• Linux >= 9d02a4283e9ce4e9ca11ff00615bdacdb0515a1a < a520e8cac54fb403f3800125b606f55fcad42cb9
• Linux >= 9d02a4283e9ce4e9ca11ff00615bdacdb0515a1a < d64a75369cd0f2ee79afcc9d9ca34a3890989379
• Linux >= 9d02a4283e9ce4e9ca11ff00615bdacdb0515a1a < b53435c079c78f89f70a62dd5a322cca4e292b34
• Linux >= 9d02a4283e9ce4e9ca11ff00615bdacdb0515a1a < 78004e9a87f240df03e2f73120d291763c32e0a7
• Linux 3.1

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Moderate · updated 2026-09-18 · vex