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/asm-generic/flat.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) create mode 100644 include/asm-generic/flat.h (limited to 'include/asm-generic/flat.h') diff --git a/include/asm-generic/flat.h b/include/asm-generic/flat.h new file mode 100644 index 000000000..1928a3596 --- /dev/null +++ b/include/asm-generic/flat.h @@ -0,0 +1,26 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_GENERIC_FLAT_H +#define _ASM_GENERIC_FLAT_H + +#include + +static inline int flat_get_addr_from_rp(u32 __user *rp, u32 relval, u32 flags, + u32 *addr) +{ +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS + return copy_from_user(addr, rp, 4) ? -EFAULT : 0; +#else + return get_user(*addr, rp); +#endif +} + +static inline int flat_put_addr_at_rp(u32 __user *rp, u32 addr, u32 rel) +{ +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS + return copy_to_user(rp, &addr, 4) ? -EFAULT : 0; +#else + return put_user(addr, rp); +#endif +} + +#endif /* _ASM_GENERIC_FLAT_H */ -- cgit v1.3.1