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/riscv/lib/memset.S | 115 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) create mode 100644 arch/riscv/lib/memset.S (limited to 'arch/riscv/lib/memset.S') diff --git a/arch/riscv/lib/memset.S b/arch/riscv/lib/memset.S new file mode 100644 index 000000000..da23b8347 --- /dev/null +++ b/arch/riscv/lib/memset.S @@ -0,0 +1,115 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2013 Regents of the University of California + */ + + +#include +#include + +/* void *memset(void *, int, size_t) */ +SYM_FUNC_START(__memset) + move t0, a0 /* Preserve return value */ + + /* Defer to byte-oriented fill for small sizes */ + sltiu a3, a2, 16 + bnez a3, 4f + + /* + * Round to nearest XLEN-aligned address + * greater than or equal to start address + */ + addi a3, t0, SZREG-1 + andi a3, a3, ~(SZREG-1) + beq a3, t0, 2f /* Skip if already aligned */ + /* Handle initial misalignment */ + sub a4, a3, t0 +1: + sb a1, 0(t0) + addi t0, t0, 1 + bltu t0, a3, 1b + sub a2, a2, a4 /* Update count */ + +2: /* Duff's device with 32 XLEN stores per iteration */ + /* Broadcast value into all bytes */ + andi a1, a1, 0xff + slli a3, a1, 8 + or a1, a3, a1 + slli a3, a1, 16 + or a1, a3, a1 +#ifdef CONFIG_64BIT + slli a3, a1, 32 + or a1, a3, a1 +#endif + + /* Calculate end address */ + andi a4, a2, ~(SZREG-1) + add a3, t0, a4 + + andi a4, a4, 31*SZREG /* Calculate remainder */ + beqz a4, 3f /* Shortcut if no remainder */ + neg a4, a4 + addi a4, a4, 32*SZREG /* Calculate initial offset */ + + /* Adjust start address with offset */ + sub t0, t0, a4 + + /* Jump into loop body */ + /* Assumes 32-bit instruction lengths */ + la a5, 3f +#ifdef CONFIG_64BIT + srli a4, a4, 1 +#endif + add a5, a5, a4 + jr a5 +3: + REG_S a1, 0(t0) + REG_S a1, SZREG(t0) + REG_S a1, 2*SZREG(t0) + REG_S a1, 3*SZREG(t0) + REG_S a1, 4*SZREG(t0) + REG_S a1, 5*SZREG(t0) + REG_S a1, 6*SZREG(t0) + REG_S a1, 7*SZREG(t0) + REG_S a1, 8*SZREG(t0) + REG_S a1, 9*SZREG(t0) + REG_S a1, 10*SZREG(t0) + REG_S a1, 11*SZREG(t0) + REG_S a1, 12*SZREG(t0) + REG_S a1, 13*SZREG(t0) + REG_S a1, 14*SZREG(t0) + REG_S a1, 15*SZREG(t0) + REG_S a1, 16*SZREG(t0) + REG_S a1, 17*SZREG(t0) + REG_S a1, 18*SZREG(t0) + REG_S a1, 19*SZREG(t0) + REG_S a1, 20*SZREG(t0) + REG_S a1, 21*SZREG(t0) + REG_S a1, 22*SZREG(t0) + REG_S a1, 23*SZREG(t0) + REG_S a1, 24*SZREG(t0) + REG_S a1, 25*SZREG(t0) + REG_S a1, 26*SZREG(t0) + REG_S a1, 27*SZREG(t0) + REG_S a1, 28*SZREG(t0) + REG_S a1, 29*SZREG(t0) + REG_S a1, 30*SZREG(t0) + REG_S a1, 31*SZREG(t0) + addi t0, t0, 32*SZREG + bltu t0, a3, 3b + andi a2, a2, SZREG-1 /* Update count */ + +4: + /* Handle trailing misalignment */ + beqz a2, 6f + add a3, t0, a2 +5: + sb a1, 0(t0) + addi t0, t0, 1 + bltu t0, a3, 5b +6: + ret +SYM_FUNC_END(__memset) +SYM_FUNC_ALIAS_WEAK(memset, __memset) +SYM_FUNC_ALIAS(__pi_memset, __memset) +SYM_FUNC_ALIAS(__pi___memset, __memset) -- cgit v1.3.1