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/mips/mm/extable.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) create mode 100644 arch/mips/mm/extable.c (limited to 'arch/mips/mm/extable.c') diff --git a/arch/mips/mm/extable.c b/arch/mips/mm/extable.c new file mode 100644 index 000000000..81bc8a34a --- /dev/null +++ b/arch/mips/mm/extable.c @@ -0,0 +1,25 @@ +/* + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * Copyright (C) 1997, 99, 2001 - 2004 Ralf Baechle + */ +#include +#include +#include +#include + +int fixup_exception(struct pt_regs *regs) +{ + const struct exception_table_entry *fixup; + + fixup = search_exception_tables(exception_epc(regs)); + if (fixup) { + regs->cp0_epc = fixup->nextinsn; + + return 1; + } + + return 0; +} -- cgit v1.3.1