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/dma.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) create mode 100644 include/asm-generic/dma.h (limited to 'include/asm-generic/dma.h') diff --git a/include/asm-generic/dma.h b/include/asm-generic/dma.h new file mode 100644 index 000000000..43d0c8af8 --- /dev/null +++ b/include/asm-generic/dma.h @@ -0,0 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_GENERIC_DMA_H +#define __ASM_GENERIC_DMA_H +/* + * This file traditionally describes the i8237 PC style DMA controller. + * Most architectures don't have these any more and can get the minimal + * implementation from kernel/dma.c by not defining MAX_DMA_CHANNELS. + * + * Some code relies on seeing MAX_DMA_ADDRESS though. + */ +#define MAX_DMA_ADDRESS PAGE_OFFSET + +extern int request_dma(unsigned int dmanr, const char *device_id); +extern void free_dma(unsigned int dmanr); + +#endif /* __ASM_GENERIC_DMA_H */ -- cgit v1.3.1