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/mmu_context.h | 76 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 include/asm-generic/mmu_context.h (limited to 'include/asm-generic/mmu_context.h') diff --git a/include/asm-generic/mmu_context.h b/include/asm-generic/mmu_context.h new file mode 100644 index 000000000..91727065b --- /dev/null +++ b/include/asm-generic/mmu_context.h @@ -0,0 +1,76 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_GENERIC_MMU_CONTEXT_H +#define __ASM_GENERIC_MMU_CONTEXT_H + +/* + * Generic hooks to implement no-op functionality. + */ + +struct task_struct; +struct mm_struct; + +/* + * enter_lazy_tlb - Called when "tsk" is about to enter lazy TLB mode. + * + * @mm: the currently active mm context which is becoming lazy + * @tsk: task which is entering lazy tlb + * + * tsk->mm will be NULL + */ +#ifndef enter_lazy_tlb +static inline void enter_lazy_tlb(struct mm_struct *mm, + struct task_struct *tsk) +{ +} +#endif + +/** + * init_new_context - Initialize context of a new mm_struct. + * @tsk: task struct for the mm + * @mm: the new mm struct + * @return: 0 on success, -errno on failure + */ +#ifndef init_new_context +static inline int init_new_context(struct task_struct *tsk, + struct mm_struct *mm) +{ + return 0; +} +#endif + +/** + * destroy_context - Undo init_new_context when the mm is going away + * @mm: old mm struct + */ +#ifndef destroy_context +static inline void destroy_context(struct mm_struct *mm) +{ +} +#endif + +/** + * activate_mm - called after exec switches the current task to a new mm, to switch to it + * @prev_mm: previous mm of this task + * @next_mm: new mm + */ +#ifndef activate_mm +static inline void activate_mm(struct mm_struct *prev_mm, + struct mm_struct *next_mm) +{ + switch_mm(prev_mm, next_mm, current); +} +#endif + +/** + * dectivate_mm - called when an mm is released after exit or exec switches away from it + * @tsk: the task + * @mm: the old mm + */ +#ifndef deactivate_mm +static inline void deactivate_mm(struct task_struct *tsk, + struct mm_struct *mm) +{ +} +#endif + +#endif /* __ASM_GENERIC_MMU_CONTEXT_H */ -- cgit v1.3.1