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/mach-versatile/hotplug.c | 102 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 102 insertions(+) create mode 100644 arch/arm/mach-versatile/hotplug.c (limited to 'arch/arm/mach-versatile/hotplug.c') diff --git a/arch/arm/mach-versatile/hotplug.c b/arch/arm/mach-versatile/hotplug.c new file mode 100644 index 000000000..5a1521755 --- /dev/null +++ b/arch/arm/mach-versatile/hotplug.c @@ -0,0 +1,102 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2002 ARM Ltd. + * All Rights Reserved + * + * This hotplug implementation is _specific_ to the situation found on + * ARM development platforms where there is _no_ possibility of actually + * taking a CPU offline, resetting it, or otherwise. Real platforms must + * NOT copy this code. + */ +#include +#include +#include + +#include +#include + +#include "platsmp.h" + +static inline void versatile_immitation_enter_lowpower(unsigned int actrl_mask) +{ + unsigned int v; + + asm volatile( + "mcr p15, 0, %1, c7, c5, 0\n" + " mcr p15, 0, %1, c7, c10, 4\n" + /* + * Turn off coherency + */ + " mrc p15, 0, %0, c1, c0, 1\n" + " bic %0, %0, %3\n" + " mcr p15, 0, %0, c1, c0, 1\n" + " mrc p15, 0, %0, c1, c0, 0\n" + " bic %0, %0, %2\n" + " mcr p15, 0, %0, c1, c0, 0\n" + : "=&r" (v) + : "r" (0), "Ir" (CR_C), "Ir" (actrl_mask) + : "cc"); +} + +static inline void versatile_immitation_leave_lowpower(unsigned int actrl_mask) +{ + unsigned int v; + + asm volatile( + "mrc p15, 0, %0, c1, c0, 0\n" + " orr %0, %0, %1\n" + " mcr p15, 0, %0, c1, c0, 0\n" + " mrc p15, 0, %0, c1, c0, 1\n" + " orr %0, %0, %2\n" + " mcr p15, 0, %0, c1, c0, 1\n" + : "=&r" (v) + : "Ir" (CR_C), "Ir" (actrl_mask) + : "cc"); +} + +static inline void versatile_immitation_do_lowpower(unsigned int cpu, int *spurious) +{ + /* + * there is no power-control hardware on this platform, so all + * we can do is put the core into WFI; this is safe as the calling + * code will have already disabled interrupts. + * + * This code should not be used outside Versatile platforms. + */ + for (;;) { + wfi(); + + if (versatile_cpu_release == cpu_logical_map(cpu)) { + /* + * OK, proper wakeup, we're done + */ + break; + } + + /* + * Getting here, means that we have come out of WFI without + * having been woken up - this shouldn't happen + * + * Just note it happening - when we're woken, we can report + * its occurrence. + */ + (*spurious)++; + } +} + +/* + * platform-specific code to shutdown a CPU. + * This code supports immitation-style CPU hotplug for Versatile/Realview/ + * Versatile Express platforms that are unable to do real CPU hotplug. + */ +void versatile_immitation_cpu_die(unsigned int cpu, unsigned int actrl_mask) +{ + int spurious = 0; + + versatile_immitation_enter_lowpower(actrl_mask); + versatile_immitation_do_lowpower(cpu, &spurious); + versatile_immitation_leave_lowpower(actrl_mask); + + if (spurious) + pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious); +} -- cgit v1.3.1