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/arm/lib/getuser.S | 167 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 167 insertions(+) create mode 100644 arch/arm/lib/getuser.S (limited to 'arch/arm/lib/getuser.S') diff --git a/arch/arm/lib/getuser.S b/arch/arm/lib/getuser.S new file mode 100644 index 000000000..c5e420750 --- /dev/null +++ b/arch/arm/lib/getuser.S @@ -0,0 +1,167 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/getuser.S + * + * Copyright (C) 2001 Russell King + * + * Idea from x86 version, (C) Copyright 1998 Linus Torvalds + * + * These functions have a non-standard call interface to make them more + * efficient, especially as they return an error value in addition to + * the "real" return value. + * + * __get_user_X + * + * Inputs: r0 contains the address + * r1 contains the address limit, which must be preserved + * Outputs: r0 is the error code + * r2, r3 contains the zero-extended value + * lr corrupted + * + * No other registers must be altered. (see + * for specific ASM register usage). + * + * Note that ADDR_LIMIT is either 0 or 0xc0000000. + * Note also that it is intended that __get_user_bad is not global. + */ +#include +#include +#include +#include + +ENTRY(__get_user_1) + check_uaccess r0, 1, r1, r2, __get_user_bad +1: TUSER(ldrb) r2, [r0] + mov r0, #0 + ret lr +ENDPROC(__get_user_1) +_ASM_NOKPROBE(__get_user_1) + +ENTRY(__get_user_2) + check_uaccess r0, 2, r1, r2, __get_user_bad +#if __LINUX_ARM_ARCH__ >= 6 + +2: TUSER(ldrh) r2, [r0] + +#else + +#ifdef CONFIG_CPU_USE_DOMAINS +rb .req ip +2: ldrbt r2, [r0], #1 +3: ldrbt rb, [r0], #0 +#else +rb .req r0 +2: ldrb r2, [r0] +3: ldrb rb, [r0, #1] +#endif +#ifndef __ARMEB__ + orr r2, r2, rb, lsl #8 +#else + orr r2, rb, r2, lsl #8 +#endif + +#endif /* __LINUX_ARM_ARCH__ >= 6 */ + + mov r0, #0 + ret lr +ENDPROC(__get_user_2) +_ASM_NOKPROBE(__get_user_2) + +ENTRY(__get_user_4) + check_uaccess r0, 4, r1, r2, __get_user_bad +4: TUSER(ldr) r2, [r0] + mov r0, #0 + ret lr +ENDPROC(__get_user_4) +_ASM_NOKPROBE(__get_user_4) + +ENTRY(__get_user_8) + check_uaccess r0, 8, r1, r2, __get_user_bad8 +#ifdef CONFIG_THUMB2_KERNEL +5: TUSER(ldr) r2, [r0] +6: TUSER(ldr) r3, [r0, #4] +#else +5: TUSER(ldr) r2, [r0], #4 +6: TUSER(ldr) r3, [r0] +#endif + mov r0, #0 + ret lr +ENDPROC(__get_user_8) +_ASM_NOKPROBE(__get_user_8) + +#ifdef __ARMEB__ +ENTRY(__get_user_32t_8) + check_uaccess r0, 8, r1, r2, __get_user_bad +#ifdef CONFIG_CPU_USE_DOMAINS + add r0, r0, #4 +7: ldrt r2, [r0] +#else +7: ldr r2, [r0, #4] +#endif + mov r0, #0 + ret lr +ENDPROC(__get_user_32t_8) +_ASM_NOKPROBE(__get_user_32t_8) + +ENTRY(__get_user_64t_1) + check_uaccess r0, 1, r1, r2, __get_user_bad8 +8: TUSER(ldrb) r3, [r0] + mov r0, #0 + ret lr +ENDPROC(__get_user_64t_1) +_ASM_NOKPROBE(__get_user_64t_1) + +ENTRY(__get_user_64t_2) + check_uaccess r0, 2, r1, r2, __get_user_bad8 +#ifdef CONFIG_CPU_USE_DOMAINS +rb .req ip +9: ldrbt r3, [r0], #1 +10: ldrbt rb, [r0], #0 +#else +rb .req r0 +9: ldrb r3, [r0] +10: ldrb rb, [r0, #1] +#endif + orr r3, rb, r3, lsl #8 + mov r0, #0 + ret lr +ENDPROC(__get_user_64t_2) +_ASM_NOKPROBE(__get_user_64t_2) + +ENTRY(__get_user_64t_4) + check_uaccess r0, 4, r1, r2, __get_user_bad8 +11: TUSER(ldr) r3, [r0] + mov r0, #0 + ret lr +ENDPROC(__get_user_64t_4) +_ASM_NOKPROBE(__get_user_64t_4) +#endif + +__get_user_bad8: + mov r3, #0 +__get_user_bad: + mov r2, #0 + mov r0, #-EFAULT + ret lr +ENDPROC(__get_user_bad) +ENDPROC(__get_user_bad8) +_ASM_NOKPROBE(__get_user_bad) +_ASM_NOKPROBE(__get_user_bad8) + +.pushsection __ex_table, "a" + .long 1b, __get_user_bad + .long 2b, __get_user_bad +#if __LINUX_ARM_ARCH__ < 6 + .long 3b, __get_user_bad +#endif + .long 4b, __get_user_bad + .long 5b, __get_user_bad8 + .long 6b, __get_user_bad8 +#ifdef __ARMEB__ + .long 7b, __get_user_bad + .long 8b, __get_user_bad8 + .long 9b, __get_user_bad8 + .long 10b, __get_user_bad8 + .long 11b, __get_user_bad8 +#endif +.popsection -- cgit v1.3.1