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/vdso/page.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 include/vdso/page.h (limited to 'include/vdso/page.h') diff --git a/include/vdso/page.h b/include/vdso/page.h new file mode 100644 index 000000000..bc47186c0 --- /dev/null +++ b/include/vdso/page.h @@ -0,0 +1,31 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __VDSO_PAGE_H +#define __VDSO_PAGE_H + +#include + +/* + * PAGE_SHIFT determines the page size. + * + * Note: This definition is required because PAGE_SHIFT is used + * in several places throughout the codebase. + */ +#define PAGE_SHIFT CONFIG_PAGE_SHIFT + +#define PAGE_SIZE (_AC(1,UL) << CONFIG_PAGE_SHIFT) + +#if !defined(CONFIG_64BIT) +/* + * Applies only to 32-bit architectures. + * + * Subtle: (1 << CONFIG_PAGE_SHIFT) is an int, not an unsigned long. + * So if we assign PAGE_MASK to a larger type it gets extended the + * way we want (i.e. with 1s in the high bits) while masking a + * 64-bit value such as phys_addr_t. + */ +#define PAGE_MASK (~((1 << CONFIG_PAGE_SHIFT) - 1)) +#else +#define PAGE_MASK (~(PAGE_SIZE - 1)) +#endif + +#endif /* __VDSO_PAGE_H */ -- cgit v1.3.1