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 --- include/uapi/asm-generic/ucontext.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) create mode 100644 include/uapi/asm-generic/ucontext.h (limited to 'include/uapi/asm-generic/ucontext.h') diff --git a/include/uapi/asm-generic/ucontext.h b/include/uapi/asm-generic/ucontext.h new file mode 100644 index 000000000..351868a72 --- /dev/null +++ b/include/uapi/asm-generic/ucontext.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef __ASM_GENERIC_UCONTEXT_H +#define __ASM_GENERIC_UCONTEXT_H + +struct ucontext { + unsigned long uc_flags; + struct ucontext *uc_link; + stack_t uc_stack; + struct sigcontext uc_mcontext; + sigset_t uc_sigmask; /* mask last for extensibility */ +}; + +#endif /* __ASM_GENERIC_UCONTEXT_H */ -- cgit v1.3.1