diff options
Diffstat (limited to 'arch/powerpc/mm/fault.c')
| -rw-r--r-- | arch/powerpc/mm/fault.c | 55 |
1 files changed, 40 insertions, 15 deletions
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 887f11bcf330..ec6b7ad70659 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -1,3 +1,4 @@ +// SPDX-License-Identifier: GPL-2.0-or-later /* * PowerPC version * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) @@ -8,11 +9,6 @@ * Modified by Cort Dougan and Paul Mackerras. * * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com) - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public License - * as published by the Free Software Foundation; either version - * 2 of the License, or (at your option) any later version. */ #include <linux/signal.h> @@ -44,6 +40,7 @@ #include <asm/mmu_context.h> #include <asm/siginfo.h> #include <asm/debug.h> +#include <asm/kup.h> static inline bool notify_page_fault(struct pt_regs *regs) { @@ -223,19 +220,46 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, } /* Is this a bad kernel fault ? */ -static bool bad_kernel_fault(bool is_exec, unsigned long error_code, - unsigned long address) +static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, + unsigned long address, bool is_write) { + int is_exec = TRAP(regs) == 0x400; + /* NX faults set DSISR_PROTFAULT on the 8xx, DSISR_NOEXEC_OR_G on others */ if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT | DSISR_PROTFAULT))) { - printk_ratelimited(KERN_CRIT "kernel tried to execute" - " exec-protected page (%lx) -" - "exploit attempt? (uid: %d)\n", - address, from_kuid(&init_user_ns, - current_uid())); + pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n", + address >= TASK_SIZE ? "exec-protected" : "user", + address, + from_kuid(&init_user_ns, current_uid())); + + // Kernel exec fault is always bad + return true; } - return is_exec || (address >= TASK_SIZE); + + if (!is_exec && address < TASK_SIZE && (error_code & DSISR_PROTFAULT) && + !search_exception_tables(regs->nip)) { + pr_crit_ratelimited("Kernel attempted to access user page (%lx) - exploit attempt? (uid: %d)\n", + address, + from_kuid(&init_user_ns, current_uid())); + } + + // Kernel fault on kernel address is bad + if (address >= TASK_SIZE) + return true; + + // Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad + if (!search_exception_tables(regs->nip)) + return true; + + // Read/write fault in a valid region (the exception table search passed + // above), but blocked by KUAP is bad, it can never succeed. + if (bad_kuap_fault(regs, is_write)) + return true; + + // What's left? Kernel fault on user in well defined regions (extable + // matched), and allowed by KUAP in the faulting context. + return false; } static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address, @@ -455,9 +479,10 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, /* * The kernel should never take an execute fault nor should it - * take a page fault to a kernel address. + * take a page fault to a kernel address or a page fault to a user + * address outside of dedicated places */ - if (unlikely(!is_user && bad_kernel_fault(is_exec, error_code, address))) + if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write))) return SIGSEGV; /* |