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 --- arch/x86/boot/bitops.h | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 arch/x86/boot/bitops.h (limited to 'arch/x86/boot/bitops.h') diff --git a/arch/x86/boot/bitops.h b/arch/x86/boot/bitops.h new file mode 100644 index 000000000..79e159715 --- /dev/null +++ b/arch/x86/boot/bitops.h @@ -0,0 +1,44 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* -*- linux-c -*- ------------------------------------------------------- * + * + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright 2007 rPath, Inc. - All Rights Reserved + * + * ----------------------------------------------------------------------- */ + +/* + * Very simple bitops for the boot code. + */ + +#ifndef BOOT_BITOPS_H +#define BOOT_BITOPS_H +#define _LINUX_BITOPS_H /* Inhibit inclusion of */ + +#include +#include + +static inline bool constant_test_bit(int nr, const void *addr) +{ + const u32 *p = addr; + return ((1UL << (nr & 31)) & (p[nr >> 5])) != 0; +} +static inline bool variable_test_bit(int nr, const void *addr) +{ + bool v; + const u32 *p = addr; + + asm("btl %2,%1" : "=@ccc" (v) : "m" (*p), "Ir" (nr)); + return v; +} + +#define test_bit(nr,addr) \ +(__builtin_constant_p(nr) ? \ + constant_test_bit((nr),(addr)) : \ + variable_test_bit((nr),(addr))) + +static inline void set_bit(int nr, void *addr) +{ + asm("btsl %1,%0" : "+m" (*(u32 *)addr) : "Ir" (nr)); +} + +#endif /* BOOT_BITOPS_H */ -- cgit v1.3.1