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/quad.S | 58 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 arch/powerpc/lib/quad.S (limited to 'arch/powerpc/lib/quad.S') diff --git a/arch/powerpc/lib/quad.S b/arch/powerpc/lib/quad.S new file mode 100644 index 000000000..da71760e5 --- /dev/null +++ b/arch/powerpc/lib/quad.S @@ -0,0 +1,58 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * Quadword loads and stores + * for use in instruction emulation. + * + * Copyright 2017 Paul Mackerras, IBM Corp. + */ + +#include +#include +#include +#include +#include +#include + +/* do_lq(unsigned long ea, unsigned long *regs) */ +_GLOBAL(do_lq) +1: lq r6, 0(r3) + std r6, 0(r4) + std r7, 8(r4) + li r3, 0 + blr +2: li r3, -EFAULT + blr + EX_TABLE(1b, 2b) + +/* do_stq(unsigned long ea, unsigned long val0, unsigned long val1) */ +_GLOBAL(do_stq) +1: stq r4, 0(r3) + li r3, 0 + blr +2: li r3, -EFAULT + blr + EX_TABLE(1b, 2b) + +/* do_lqarx(unsigned long ea, unsigned long *regs) */ +_GLOBAL(do_lqarx) +1: PPC_LQARX(6, 0, 3, 0) + std r6, 0(r4) + std r7, 8(r4) + li r3, 0 + blr +2: li r3, -EFAULT + blr + EX_TABLE(1b, 2b) + +/* do_stqcx(unsigned long ea, unsigned long val0, unsigned long val1, + unsigned int *crp) */ + +_GLOBAL(do_stqcx) +1: PPC_STQCX(4, 0, 3) + mfcr r5 + stw r5, 0(r6) + li r3, 0 + blr +2: li r3, -EFAULT + blr + EX_TABLE(1b, 2b) -- cgit v1.3.1