| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* |
| * PowerPC version |
| * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) |
| * |
| * Derived from "arch/i386/mm/fault.c" |
| * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
| * |
| * Modified by Cort Dougan and Paul Mackerras. |
| * |
| * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com) |
| */ |
| |
| #include <linux/signal.h> |
| #include <linux/sched.h> |
| #include <linux/sched/task_stack.h> |
| #include <linux/kernel.h> |
| #include <linux/errno.h> |
| #include <linux/string.h> |
| #include <linux/types.h> |
| #include <linux/pagemap.h> |
| #include <linux/ptrace.h> |
| #include <linux/mman.h> |
| #include <linux/mm.h> |
| #include <linux/interrupt.h> |
| #include <linux/highmem.h> |
| #include <linux/extable.h> |
| #include <linux/kprobes.h> |
| #include <linux/kdebug.h> |
| #include <linux/perf_event.h> |
| #include <linux/ratelimit.h> |
| #include <linux/context_tracking.h> |
| #include <linux/hugetlb.h> |
| #include <linux/uaccess.h> |
| #include <linux/kfence.h> |
| #include <linux/pkeys.h> |
| |
| #include <asm/firmware.h> |
| #include <asm/interrupt.h> |
| #include <asm/page.h> |
| #include <asm/mmu.h> |
| #include <asm/mmu_context.h> |
| #include <asm/siginfo.h> |
| #include <asm/debug.h> |
| #include <asm/kup.h> |
| #include <asm/inst.h> |
| |
| |
| /* |
| * do_page_fault error handling helpers |
| */ |
| |
| static int |
| __bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code) |
| { |
| /* |
| * If we are in kernel mode, bail out with a SEGV, this will |
| * be caught by the assembly which will restore the non-volatile |
| * registers before calling bad_page_fault() |
| */ |
| if (!user_mode(regs)) |
| return SIGSEGV; |
| |
| _exception(SIGSEGV, regs, si_code, address); |
| |
| return 0; |
| } |
| |
| static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address) |
| { |
| return __bad_area_nosemaphore(regs, address, SEGV_MAPERR); |
| } |
| |
| static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code) |
| { |
| struct mm_struct *mm = current->mm; |
| |
| /* |
| * Something tried to access memory that isn't in our memory map.. |
| * Fix it, but check if it's kernel or user first.. |
| */ |
| mmap_read_unlock(mm); |
| |
| return __bad_area_nosemaphore(regs, address, si_code); |
| } |
| |
| static noinline int bad_area(struct pt_regs *regs, unsigned long address) |
| { |
| return __bad_area(regs, address, SEGV_MAPERR); |
| } |
| |
| static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address, |
| struct vm_area_struct *vma) |
| { |
| struct mm_struct *mm = current->mm; |
| int pkey; |
| |
| /* |
| * We don't try to fetch the pkey from page table because reading |
| * page table without locking doesn't guarantee stable pte value. |
| * Hence the pkey value that we return to userspace can be different |
| * from the pkey that actually caused access error. |
| * |
| * It does *not* guarantee that the VMA we find here |
| * was the one that we faulted on. |
| * |
| * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); |
| * 2. T1 : set AMR to deny access to pkey=4, touches, page |
| * 3. T1 : faults... |
| * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); |
| * 5. T1 : enters fault handler, takes mmap_lock, etc... |
| * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really |
| * faulted on a pte with its pkey=4. |
| */ |
| pkey = vma_pkey(vma); |
| |
| mmap_read_unlock(mm); |
| |
| /* |
| * If we are in kernel mode, bail out with a SEGV, this will |
| * be caught by the assembly which will restore the non-volatile |
| * registers before calling bad_page_fault() |
| */ |
| if (!user_mode(regs)) |
| return SIGSEGV; |
| |
| _exception_pkey(regs, address, pkey); |
| |
| return 0; |
| } |
| |
| static noinline int bad_access(struct pt_regs *regs, unsigned long address) |
| { |
| return __bad_area(regs, address, SEGV_ACCERR); |
| } |
| |
| static int do_sigbus(struct pt_regs *regs, unsigned long address, |
| vm_fault_t fault) |
| { |
| if (!user_mode(regs)) |
| return SIGBUS; |
| |
| current->thread.trap_nr = BUS_ADRERR; |
| #ifdef CONFIG_MEMORY_FAILURE |
| if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { |
| unsigned int lsb = 0; /* shutup gcc */ |
| |
| pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", |
| current->comm, current->pid, address); |
| |
| if (fault & VM_FAULT_HWPOISON_LARGE) |
| lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); |
| if (fault & VM_FAULT_HWPOISON) |
| lsb = PAGE_SHIFT; |
| |
| force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb); |
| return 0; |
| } |
| |
| #endif |
| force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); |
| return 0; |
| } |
| |
| static int mm_fault_error(struct pt_regs *regs, unsigned long addr, |
| vm_fault_t fault) |
| { |
| /* |
| * Kernel page fault interrupted by SIGKILL. We have no reason to |
| * continue processing. |
| */ |
| if (fatal_signal_pending(current) && !user_mode(regs)) |
| return SIGKILL; |
| |
| /* Out of memory */ |
| if (fault & VM_FAULT_OOM) { |
| /* |
| * We ran out of memory, or some other thing happened to us that |
| * made us unable to handle the page fault gracefully. |
| */ |
| if (!user_mode(regs)) |
| return SIGSEGV; |
| pagefault_out_of_memory(); |
| } else { |
| if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| |
| VM_FAULT_HWPOISON_LARGE)) |
| return do_sigbus(regs, addr, fault); |
| else if (fault & VM_FAULT_SIGSEGV) |
| return bad_area_nosemaphore(regs, addr); |
| else |
| BUG(); |
| } |
| return 0; |
| } |
| |
| /* Is this a bad kernel fault ? */ |
| static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, |
| unsigned long address, bool is_write) |
| { |
| int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE; |
| |
| if (is_exec) { |
| 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; |
| } |
| |
| // Kernel fault on kernel address is bad |
| if (address >= TASK_SIZE) |
| return true; |
| |
| // Read/write fault blocked by KUAP is bad, it can never succeed. |
| if (bad_kuap_fault(regs, address, is_write)) { |
| pr_crit_ratelimited("Kernel attempted to %s user page (%lx) - exploit attempt? (uid: %d)\n", |
| is_write ? "write" : "read", address, |
| from_kuid(&init_user_ns, current_uid())); |
| |
| // 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. |
| return WARN(true, "Bug: %s fault blocked by KUAP!", is_write ? "Write" : "Read"); |
| } |
| |
| // What's left? Kernel fault on user and allowed by KUAP in the faulting context. |
| return false; |
| } |
| |
| static bool access_pkey_error(bool is_write, bool is_exec, bool is_pkey, |
| struct vm_area_struct *vma) |
| { |
| /* |
| * Make sure to check the VMA so that we do not perform |
| * faults just to hit a pkey fault as soon as we fill in a |
| * page. Only called for current mm, hence foreign == 0 |
| */ |
| if (!arch_vma_access_permitted(vma, is_write, is_exec, 0)) |
| return true; |
| |
| return false; |
| } |
| |
| static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma) |
| { |
| /* |
| * Allow execution from readable areas if the MMU does not |
| * provide separate controls over reading and executing. |
| * |
| * Note: That code used to not be enabled for 4xx/BookE. |
| * It is now as I/D cache coherency for these is done at |
| * set_pte_at() time and I see no reason why the test |
| * below wouldn't be valid on those processors. This -may- |
| * break programs compiled with a really old ABI though. |
| */ |
| if (is_exec) { |
| return !(vma->vm_flags & VM_EXEC) && |
| (cpu_has_feature(CPU_FTR_NOEXECUTE) || |
| !(vma->vm_flags & (VM_READ | VM_WRITE))); |
| } |
| |
| if (is_write) { |
| if (unlikely(!(vma->vm_flags & VM_WRITE))) |
| return true; |
| return false; |
| } |
| |
| if (unlikely(!vma_is_accessible(vma))) |
| return true; |
| /* |
| * We should ideally do the vma pkey access check here. But in the |
| * fault path, handle_mm_fault() also does the same check. To avoid |
| * these multiple checks, we skip it here and handle access error due |
| * to pkeys later. |
| */ |
| return false; |
| } |
| |
| #ifdef CONFIG_PPC_SMLPAR |
| static inline void cmo_account_page_fault(void) |
| { |
| if (firmware_has_feature(FW_FEATURE_CMO)) { |
| u32 page_ins; |
| |
| preempt_disable(); |
| page_ins = be32_to_cpu(get_lppaca()->page_ins); |
| page_ins += 1 << PAGE_FACTOR; |
| get_lppaca()->page_ins = cpu_to_be32(page_ins); |
| preempt_enable(); |
| } |
| } |
| #else |
| static inline void cmo_account_page_fault(void) { } |
| #endif /* CONFIG_PPC_SMLPAR */ |
| |
| static void sanity_check_fault(bool is_write, bool is_user, |
| unsigned long error_code, unsigned long address) |
| { |
| /* |
| * Userspace trying to access kernel address, we get PROTFAULT for that. |
| */ |
| if (is_user && address >= TASK_SIZE) { |
| if ((long)address == -1) |
| return; |
| |
| pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n", |
| current->comm, current->pid, address, |
| from_kuid(&init_user_ns, current_uid())); |
| return; |
| } |
| |
| if (!IS_ENABLED(CONFIG_PPC_BOOK3S)) |
| return; |
| |
| /* |
| * For hash translation mode, we should never get a |
| * PROTFAULT. Any update to pte to reduce access will result in us |
| * removing the hash page table entry, thus resulting in a DSISR_NOHPTE |
| * fault instead of DSISR_PROTFAULT. |
| * |
| * A pte update to relax the access will not result in a hash page table |
| * entry invalidate and hence can result in DSISR_PROTFAULT. |
| * ptep_set_access_flags() doesn't do a hpte flush. This is why we have |
| * the special !is_write in the below conditional. |
| * |
| * For platforms that doesn't supports coherent icache and do support |
| * per page noexec bit, we do setup things such that we do the |
| * sync between D/I cache via fault. But that is handled via low level |
| * hash fault code (hash_page_do_lazy_icache()) and we should not reach |
| * here in such case. |
| * |
| * For wrong access that can result in PROTFAULT, the above vma->vm_flags |
| * check should handle those and hence we should fall to the bad_area |
| * handling correctly. |
| * |
| * For embedded with per page exec support that doesn't support coherent |
| * icache we do get PROTFAULT and we handle that D/I cache sync in |
| * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON |
| * is conditional for server MMU. |
| * |
| * For radix, we can get prot fault for autonuma case, because radix |
| * page table will have them marked noaccess for user. |
| */ |
| if (radix_enabled() || is_write) |
| return; |
| |
| WARN_ON_ONCE(error_code & DSISR_PROTFAULT); |
| } |
| |
| /* |
| * Define the correct "is_write" bit in error_code based |
| * on the processor family |
| */ |
| #if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) |
| #define page_fault_is_write(__err) ((__err) & ESR_DST) |
| #else |
| #define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE) |
| #endif |
| |
| #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) |
| #define page_fault_is_bad(__err) (0) |
| #elif defined(CONFIG_PPC_8xx) |
| #define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G) |
| #elif defined(CONFIG_PPC64) |
| #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S) |
| #else |
| #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S) |
| #endif |
| |
| /* |
| * For 600- and 800-family processors, the error_code parameter is DSISR |
| * for a data fault, SRR1 for an instruction fault. |
| * For 400-family processors the error_code parameter is ESR for a data fault, |
| * 0 for an instruction fault. |
| * For 64-bit processors, the error_code parameter is DSISR for a data access |
| * fault, SRR1 & 0x08000000 for an instruction access fault. |
| * |
| * The return value is 0 if the fault was handled, or the signal |
| * number if this is a kernel fault that can't be handled here. |
| */ |
| static int ___do_page_fault(struct pt_regs *regs, unsigned long address, |
| unsigned long error_code) |
| { |
| struct vm_area_struct * vma; |
| struct mm_struct *mm = current->mm; |
| unsigned int flags = FAULT_FLAG_DEFAULT; |
| int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE; |
| int is_user = user_mode(regs); |
| int is_write = page_fault_is_write(error_code); |
| vm_fault_t fault, major = 0; |
| bool kprobe_fault = kprobe_page_fault(regs, 11); |
| |
| if (unlikely(debugger_fault_handler(regs) || kprobe_fault)) |
| return 0; |
| |
| if (unlikely(page_fault_is_bad(error_code))) { |
| if (is_user) { |
| _exception(SIGBUS, regs, BUS_OBJERR, address); |
| return 0; |
| } |
| return SIGBUS; |
| } |
| |
| /* Additional sanity check(s) */ |
| sanity_check_fault(is_write, is_user, error_code, address); |
| |
| /* |
| * The kernel should never take an execute fault nor should it |
| * 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(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; |
| |
| /* The fault is fully completed (including releasing mmap lock) */ |
| if (fault & VM_FAULT_COMPLETED) |
| goto out; |
| |
| /* |
| * 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); |
| |
| out: |
| /* |
| * 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 |