651 lines
18 KiB
C
651 lines
18 KiB
C
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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* PowerPC version
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* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
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*
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* Derived from "arch/i386/mm/fault.c"
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*
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* Modified by Cort Dougan and Paul Mackerras.
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*
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* Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
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*/
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#include <linux/signal.h>
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#include <linux/sched.h>
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#include <linux/sched/task_stack.h>
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/pagemap.h>
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#include <linux/ptrace.h>
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#include <linux/mman.h>
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#include <linux/mm.h>
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#include <linux/interrupt.h>
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#include <linux/highmem.h>
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#include <linux/extable.h>
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#include <linux/kprobes.h>
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#include <linux/kdebug.h>
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#include <linux/perf_event.h>
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#include <linux/ratelimit.h>
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#include <linux/context_tracking.h>
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#include <linux/hugetlb.h>
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#include <linux/uaccess.h>
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#include <linux/kfence.h>
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#include <linux/pkeys.h>
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#include <asm/firmware.h>
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#include <asm/interrupt.h>
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#include <asm/page.h>
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#include <asm/mmu.h>
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#include <asm/mmu_context.h>
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#include <asm/siginfo.h>
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#include <asm/debug.h>
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#include <asm/kup.h>
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#include <asm/inst.h>
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/*
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* do_page_fault error handling helpers
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*/
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static int
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__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code)
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{
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/*
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* If we are in kernel mode, bail out with a SEGV, this will
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* be caught by the assembly which will restore the non-volatile
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* registers before calling bad_page_fault()
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*/
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if (!user_mode(regs))
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return SIGSEGV;
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_exception(SIGSEGV, regs, si_code, address);
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return 0;
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}
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static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)
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{
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return __bad_area_nosemaphore(regs, address, SEGV_MAPERR);
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}
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static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
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{
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struct mm_struct *mm = current->mm;
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/*
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* Something tried to access memory that isn't in our memory map..
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* Fix it, but check if it's kernel or user first..
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*/
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mmap_read_unlock(mm);
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return __bad_area_nosemaphore(regs, address, si_code);
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}
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static noinline int bad_area(struct pt_regs *regs, unsigned long address)
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{
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return __bad_area(regs, address, SEGV_MAPERR);
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}
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static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address,
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struct vm_area_struct *vma)
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{
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struct mm_struct *mm = current->mm;
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int pkey;
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/*
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* We don't try to fetch the pkey from page table because reading
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* page table without locking doesn't guarantee stable pte value.
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* Hence the pkey value that we return to userspace can be different
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* from the pkey that actually caused access error.
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*
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* It does *not* guarantee that the VMA we find here
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* was the one that we faulted on.
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*
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* 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
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* 2. T1 : set AMR to deny access to pkey=4, touches, page
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* 3. T1 : faults...
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* 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
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* 5. T1 : enters fault handler, takes mmap_lock, etc...
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* 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
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* faulted on a pte with its pkey=4.
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*/
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pkey = vma_pkey(vma);
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mmap_read_unlock(mm);
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/*
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* If we are in kernel mode, bail out with a SEGV, this will
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* be caught by the assembly which will restore the non-volatile
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* registers before calling bad_page_fault()
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*/
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if (!user_mode(regs))
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return SIGSEGV;
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_exception_pkey(regs, address, pkey);
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return 0;
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}
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static noinline int bad_access(struct pt_regs *regs, unsigned long address)
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{
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return __bad_area(regs, address, SEGV_ACCERR);
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}
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static int do_sigbus(struct pt_regs *regs, unsigned long address,
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vm_fault_t fault)
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{
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if (!user_mode(regs))
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return SIGBUS;
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current->thread.trap_nr = BUS_ADRERR;
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#ifdef CONFIG_MEMORY_FAILURE
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if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
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unsigned int lsb = 0; /* shutup gcc */
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pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
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current->comm, current->pid, address);
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if (fault & VM_FAULT_HWPOISON_LARGE)
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lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
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if (fault & VM_FAULT_HWPOISON)
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lsb = PAGE_SHIFT;
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force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
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return 0;
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}
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#endif
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force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
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return 0;
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}
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static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
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vm_fault_t fault)
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{
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/*
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* Kernel page fault interrupted by SIGKILL. We have no reason to
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* continue processing.
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*/
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if (fatal_signal_pending(current) && !user_mode(regs))
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return SIGKILL;
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/* Out of memory */
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if (fault & VM_FAULT_OOM) {
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/*
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* We ran out of memory, or some other thing happened to us that
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* made us unable to handle the page fault gracefully.
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*/
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if (!user_mode(regs))
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return SIGSEGV;
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pagefault_out_of_memory();
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} else {
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if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
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VM_FAULT_HWPOISON_LARGE))
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return do_sigbus(regs, addr, fault);
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else if (fault & VM_FAULT_SIGSEGV)
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return bad_area_nosemaphore(regs, addr);
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else
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BUG();
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}
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return 0;
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}
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/* Is this a bad kernel fault ? */
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static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
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unsigned long address, bool is_write)
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{
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int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
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if (is_exec) {
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pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n",
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address >= TASK_SIZE ? "exec-protected" : "user",
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address,
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from_kuid(&init_user_ns, current_uid()));
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// Kernel exec fault is always bad
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return true;
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}
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// Kernel fault on kernel address is bad
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if (address >= TASK_SIZE)
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return true;
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// Read/write fault blocked by KUAP is bad, it can never succeed.
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if (bad_kuap_fault(regs, address, is_write)) {
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pr_crit_ratelimited("Kernel attempted to %s user page (%lx) - exploit attempt? (uid: %d)\n",
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is_write ? "write" : "read", address,
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from_kuid(&init_user_ns, current_uid()));
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// Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad
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if (!search_exception_tables(regs->nip))
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return true;
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// Read/write fault in a valid region (the exception table search passed
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// above), but blocked by KUAP is bad, it can never succeed.
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return WARN(true, "Bug: %s fault blocked by KUAP!", is_write ? "Write" : "Read");
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}
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// What's left? Kernel fault on user and allowed by KUAP in the faulting context.
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return false;
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}
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static bool access_pkey_error(bool is_write, bool is_exec, bool is_pkey,
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struct vm_area_struct *vma)
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{
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/*
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* Make sure to check the VMA so that we do not perform
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* faults just to hit a pkey fault as soon as we fill in a
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* page. Only called for current mm, hence foreign == 0
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*/
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if (!arch_vma_access_permitted(vma, is_write, is_exec, 0))
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return true;
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return false;
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}
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static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma)
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{
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/*
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* Allow execution from readable areas if the MMU does not
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* provide separate controls over reading and executing.
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*
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* Note: That code used to not be enabled for 4xx/BookE.
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* It is now as I/D cache coherency for these is done at
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* set_pte_at() time and I see no reason why the test
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* below wouldn't be valid on those processors. This -may-
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* break programs compiled with a really old ABI though.
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*/
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if (is_exec) {
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return !(vma->vm_flags & VM_EXEC) &&
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(cpu_has_feature(CPU_FTR_NOEXECUTE) ||
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!(vma->vm_flags & (VM_READ | VM_WRITE)));
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}
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if (is_write) {
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if (unlikely(!(vma->vm_flags & VM_WRITE)))
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return true;
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return false;
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}
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if (unlikely(!vma_is_accessible(vma)))
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return true;
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/*
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* We should ideally do the vma pkey access check here. But in the
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* fault path, handle_mm_fault() also does the same check. To avoid
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* these multiple checks, we skip it here and handle access error due
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* to pkeys later.
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*/
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return false;
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}
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#ifdef CONFIG_PPC_SMLPAR
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static inline void cmo_account_page_fault(void)
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{
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if (firmware_has_feature(FW_FEATURE_CMO)) {
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u32 page_ins;
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preempt_disable();
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page_ins = be32_to_cpu(get_lppaca()->page_ins);
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page_ins += 1 << PAGE_FACTOR;
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get_lppaca()->page_ins = cpu_to_be32(page_ins);
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preempt_enable();
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}
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}
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#else
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static inline void cmo_account_page_fault(void) { }
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#endif /* CONFIG_PPC_SMLPAR */
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static void sanity_check_fault(bool is_write, bool is_user,
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unsigned long error_code, unsigned long address)
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{
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/*
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* Userspace trying to access kernel address, we get PROTFAULT for that.
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*/
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if (is_user && address >= TASK_SIZE) {
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if ((long)address == -1)
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return;
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pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n",
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current->comm, current->pid, address,
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from_kuid(&init_user_ns, current_uid()));
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return;
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}
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if (!IS_ENABLED(CONFIG_PPC_BOOK3S))
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return;
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/*
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* For hash translation mode, we should never get a
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* PROTFAULT. Any update to pte to reduce access will result in us
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* removing the hash page table entry, thus resulting in a DSISR_NOHPTE
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* fault instead of DSISR_PROTFAULT.
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*
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* A pte update to relax the access will not result in a hash page table
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* entry invalidate and hence can result in DSISR_PROTFAULT.
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* ptep_set_access_flags() doesn't do a hpte flush. This is why we have
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* the special !is_write in the below conditional.
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*
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* For platforms that doesn't supports coherent icache and do support
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* per page noexec bit, we do setup things such that we do the
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* sync between D/I cache via fault. But that is handled via low level
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* hash fault code (hash_page_do_lazy_icache()) and we should not reach
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* here in such case.
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*
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* For wrong access that can result in PROTFAULT, the above vma->vm_flags
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* check should handle those and hence we should fall to the bad_area
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* handling correctly.
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*
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* For embedded with per page exec support that doesn't support coherent
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* icache we do get PROTFAULT and we handle that D/I cache sync in
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* set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON
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* is conditional for server MMU.
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*
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* For radix, we can get prot fault for autonuma case, because radix
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* page table will have them marked noaccess for user.
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*/
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if (radix_enabled() || is_write)
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return;
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WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
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}
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/*
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* Define the correct "is_write" bit in error_code based
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* on the processor family
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*/
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#if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
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#define page_fault_is_write(__err) ((__err) & ESR_DST)
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#else
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#define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE)
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#endif
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#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
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#define page_fault_is_bad(__err) (0)
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#elif defined(CONFIG_PPC_8xx)
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#define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G)
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#elif defined(CONFIG_PPC64)
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#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S)
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#else
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#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S)
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#endif
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/*
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* For 600- and 800-family processors, the error_code parameter is DSISR
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* for a data fault, SRR1 for an instruction fault.
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* For 400-family processors the error_code parameter is ESR for a data fault,
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* 0 for an instruction fault.
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* For 64-bit processors, the error_code parameter is DSISR for a data access
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* fault, SRR1 & 0x08000000 for an instruction access fault.
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*
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* The return value is 0 if the fault was handled, or the signal
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* number if this is a kernel fault that can't be handled here.
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*/
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static int ___do_page_fault(struct pt_regs *regs, unsigned long address,
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unsigned long error_code)
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{
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struct vm_area_struct * vma;
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struct mm_struct *mm = current->mm;
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unsigned int flags = FAULT_FLAG_DEFAULT;
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int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
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int is_user = user_mode(regs);
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int is_write = page_fault_is_write(error_code);
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vm_fault_t fault, major = 0;
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bool kprobe_fault = kprobe_page_fault(regs, 11);
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if (unlikely(debugger_fault_handler(regs) || kprobe_fault))
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return 0;
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if (unlikely(page_fault_is_bad(error_code))) {
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if (is_user) {
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_exception(SIGBUS, regs, BUS_OBJERR, address);
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return 0;
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}
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return SIGBUS;
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}
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/* Additional sanity check(s) */
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sanity_check_fault(is_write, is_user, error_code, address);
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/*
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* The kernel should never take an execute fault nor should it
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* take a page fault to a kernel address or a page fault to a user
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* address outside of dedicated places
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*/
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||
|
if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write))) {
|
||
|
if (kfence_handle_page_fault(address, is_write, regs))
|
||
|
return 0;
|
||
|
|
||
|
return SIGSEGV;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* If we're in an interrupt, have no user context or are running
|
||
|
* in a region with pagefaults disabled then we must not take the fault
|
||
|
*/
|
||
|
if (unlikely(faulthandler_disabled() || !mm)) {
|
||
|
if (is_user)
|
||
|
printk_ratelimited(KERN_ERR "Page fault in user mode"
|
||
|
" with faulthandler_disabled()=%d"
|
||
|
" mm=%p\n",
|
||
|
faulthandler_disabled(), mm);
|
||
|
return bad_area_nosemaphore(regs, address);
|
||
|
}
|
||
|
|
||
|
interrupt_cond_local_irq_enable(regs);
|
||
|
|
||
|
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
|
||
|
|
||
|
/*
|
||
|
* We want to do this outside mmap_lock, because reading code around nip
|
||
|
* can result in fault, which will cause a deadlock when called with
|
||
|
* mmap_lock held
|
||
|
*/
|
||
|
if (is_user)
|
||
|
flags |= FAULT_FLAG_USER;
|
||
|
if (is_write)
|
||
|
flags |= FAULT_FLAG_WRITE;
|
||
|
if (is_exec)
|
||
|
flags |= FAULT_FLAG_INSTRUCTION;
|
||
|
|
||
|
/* When running in the kernel we expect faults to occur only to
|
||
|
* addresses in user space. All other faults represent errors in the
|
||
|
* kernel and should generate an OOPS. Unfortunately, in the case of an
|
||
|
* erroneous fault occurring in a code path which already holds mmap_lock
|
||
|
* we will deadlock attempting to validate the fault against the
|
||
|
* address space. Luckily the kernel only validly references user
|
||
|
* space from well defined areas of code, which are listed in the
|
||
|
* exceptions table.
|
||
|
*
|
||
|
* As the vast majority of faults will be valid we will only perform
|
||
|
* the source reference check when there is a possibility of a deadlock.
|
||
|
* Attempt to lock the address space, if we cannot we then validate the
|
||
|
* source. If this is invalid we can skip the address space check,
|
||
|
* thus avoiding the deadlock.
|
||
|
*/
|
||
|
if (unlikely(!mmap_read_trylock(mm))) {
|
||
|
if (!is_user && !search_exception_tables(regs->nip))
|
||
|
return bad_area_nosemaphore(regs, address);
|
||
|
|
||
|
retry:
|
||
|
mmap_read_lock(mm);
|
||
|
} else {
|
||
|
/*
|
||
|
* The above down_read_trylock() might have succeeded in
|
||
|
* which case we'll have missed the might_sleep() from
|
||
|
* down_read():
|
||
|
*/
|
||
|
might_sleep();
|
||
|
}
|
||
|
|
||
|
vma = find_vma(mm, address);
|
||
|
if (unlikely(!vma))
|
||
|
return bad_area(regs, address);
|
||
|
|
||
|
if (unlikely(vma->vm_start > address)) {
|
||
|
if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
|
||
|
return bad_area(regs, address);
|
||
|
|
||
|
if (unlikely(expand_stack(vma, address)))
|
||
|
return bad_area(regs, address);
|
||
|
}
|
||
|
|
||
|
if (unlikely(access_pkey_error(is_write, is_exec,
|
||
|
(error_code & DSISR_KEYFAULT), vma)))
|
||
|
return bad_access_pkey(regs, address, vma);
|
||
|
|
||
|
if (unlikely(access_error(is_write, is_exec, vma)))
|
||
|
return bad_access(regs, address);
|
||
|
|
||
|
/*
|
||
|
* If for any reason at all we couldn't handle the fault,
|
||
|
* make sure we exit gracefully rather than endlessly redo
|
||
|
* the fault.
|
||
|
*/
|
||
|
fault = handle_mm_fault(vma, address, flags, regs);
|
||
|
|
||
|
major |= fault & VM_FAULT_MAJOR;
|
||
|
|
||
|
if (fault_signal_pending(fault, regs))
|
||
|
return user_mode(regs) ? 0 : SIGBUS;
|
||
|
|
||
|
/*
|
||
|
* Handle the retry right now, the mmap_lock has been released in that
|
||
|
* case.
|
||
|
*/
|
||
|
if (unlikely(fault & VM_FAULT_RETRY)) {
|
||
|
flags |= FAULT_FLAG_TRIED;
|
||
|
goto retry;
|
||
|
}
|
||
|
|
||
|
mmap_read_unlock(current->mm);
|
||
|
|
||
|
if (unlikely(fault & VM_FAULT_ERROR))
|
||
|
return mm_fault_error(regs, address, fault);
|
||
|
|
||
|
/*
|
||
|
* Major/minor page fault accounting.
|
||
|
*/
|
||
|
if (major)
|
||
|
cmo_account_page_fault();
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
NOKPROBE_SYMBOL(___do_page_fault);
|
||
|
|
||
|
static __always_inline void __do_page_fault(struct pt_regs *regs)
|
||
|
{
|
||
|
long err;
|
||
|
|
||
|
err = ___do_page_fault(regs, regs->dar, regs->dsisr);
|
||
|
if (unlikely(err))
|
||
|
bad_page_fault(regs, err);
|
||
|
}
|
||
|
|
||
|
DEFINE_INTERRUPT_HANDLER(do_page_fault)
|
||
|
{
|
||
|
__do_page_fault(regs);
|
||
|
}
|
||
|
|
||
|
#ifdef CONFIG_PPC_BOOK3S_64
|
||
|
/* Same as do_page_fault but interrupt entry has already run in do_hash_fault */
|
||
|
void hash__do_page_fault(struct pt_regs *regs)
|
||
|
{
|
||
|
__do_page_fault(regs);
|
||
|
}
|
||
|
NOKPROBE_SYMBOL(hash__do_page_fault);
|
||
|
#endif
|
||
|
|
||
|
/*
|
||
|
* bad_page_fault is called when we have a bad access from the kernel.
|
||
|
* It is called from the DSI and ISI handlers in head.S and from some
|
||
|
* of the procedures in traps.c.
|
||
|
*/
|
||
|
static void __bad_page_fault(struct pt_regs *regs, int sig)
|
||
|
{
|
||
|
int is_write = page_fault_is_write(regs->dsisr);
|
||
|
const char *msg;
|
||
|
|
||
|
/* kernel has accessed a bad area */
|
||
|
|
||
|
if (regs->dar < PAGE_SIZE)
|
||
|
msg = "Kernel NULL pointer dereference";
|
||
|
else
|
||
|
msg = "Unable to handle kernel data access";
|
||
|
|
||
|
switch (TRAP(regs)) {
|
||
|
case INTERRUPT_DATA_STORAGE:
|
||
|
case INTERRUPT_H_DATA_STORAGE:
|
||
|
pr_alert("BUG: %s on %s at 0x%08lx\n", msg,
|
||
|
is_write ? "write" : "read", regs->dar);
|
||
|
break;
|
||
|
case INTERRUPT_DATA_SEGMENT:
|
||
|
pr_alert("BUG: %s at 0x%08lx\n", msg, regs->dar);
|
||
|
break;
|
||
|
case INTERRUPT_INST_STORAGE:
|
||
|
case INTERRUPT_INST_SEGMENT:
|
||
|
pr_alert("BUG: Unable to handle kernel instruction fetch%s",
|
||
|
regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
|
||
|
break;
|
||
|
case INTERRUPT_ALIGNMENT:
|
||
|
pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
|
||
|
regs->dar);
|
||
|
break;
|
||
|
default:
|
||
|
pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
|
||
|
regs->dar);
|
||
|
break;
|
||
|
}
|
||
|
printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
|
||
|
regs->nip);
|
||
|
|
||
|
if (task_stack_end_corrupted(current))
|
||
|
printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
|
||
|
|
||
|
die("Kernel access of bad area", regs, sig);
|
||
|
}
|
||
|
|
||
|
void bad_page_fault(struct pt_regs *regs, int sig)
|
||
|
{
|
||
|
const struct exception_table_entry *entry;
|
||
|
|
||
|
/* Are we prepared to handle this fault? */
|
||
|
entry = search_exception_tables(instruction_pointer(regs));
|
||
|
if (entry)
|
||
|
instruction_pointer_set(regs, extable_fixup(entry));
|
||
|
else
|
||
|
__bad_page_fault(regs, sig);
|
||
|
}
|
||
|
|
||
|
#ifdef CONFIG_PPC_BOOK3S_64
|
||
|
DEFINE_INTERRUPT_HANDLER(do_bad_page_fault_segv)
|
||
|
{
|
||
|
bad_page_fault(regs, SIGSEGV);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* In radix, segment interrupts indicate the EA is not addressable by the
|
||
|
* page table geometry, so they are always sent here.
|
||
|
*
|
||
|
* In hash, this is called if do_slb_fault returns error. Typically it is
|
||
|
* because the EA was outside the region allowed by software.
|
||
|
*/
|
||
|
DEFINE_INTERRUPT_HANDLER(do_bad_segment_interrupt)
|
||
|
{
|
||
|
int err = regs->result;
|
||
|
|
||
|
if (err == -EFAULT) {
|
||
|
if (user_mode(regs))
|
||
|
_exception(SIGSEGV, regs, SEGV_BNDERR, regs->dar);
|
||
|
else
|
||
|
bad_page_fault(regs, SIGSEGV);
|
||
|
} else if (err == -EINVAL) {
|
||
|
unrecoverable_exception(regs);
|
||
|
} else {
|
||
|
BUG();
|
||
|
}
|
||
|
}
|
||
|
#endif
|