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/powerpc/lib/string.S | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 arch/powerpc/lib/string.S (limited to 'arch/powerpc/lib/string.S') diff --git a/arch/powerpc/lib/string.S b/arch/powerpc/lib/string.S new file mode 100644 index 000000000..c3f5e7d31 --- /dev/null +++ b/arch/powerpc/lib/string.S @@ -0,0 +1,43 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * String handling functions for PowerPC. + * + * Copyright (C) 1996 Paul Mackerras. + */ +#include +#include +#include + + .text + +_GLOBAL(strncmp) + PPC_LCMPI 0,r5,0 + beq- 2f + mtctr r5 + addi r5,r3,-1 + addi r4,r4,-1 + .balign IFETCH_ALIGN_BYTES +1: lbzu r3,1(r5) + cmpwi 1,r3,0 + lbzu r0,1(r4) + subf. r3,r0,r3 + beqlr 1 + bdnzt eq,1b + blr +2: li r3,0 + blr +EXPORT_SYMBOL(strncmp) + +_GLOBAL(memchr) + PPC_LCMPI 0,r5,0 + beq- 2f + mtctr r5 + addi r3,r3,-1 + .balign IFETCH_ALIGN_BYTES +1: lbzu r0,1(r3) + cmpw 0,r0,r4 + bdnzf 2,1b + beqlr +2: li r3,0 + blr +EXPORT_SYMBOL(memchr) -- cgit v1.3.1