diff options
Diffstat (limited to 'arch/powerpc/mm/fault.c')
| -rw-r--r-- | arch/powerpc/mm/fault.c | 932 |
1 files changed, 548 insertions, 384 deletions
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 8726779e1409..806c74e0d5ab 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) @@ -8,526 +9,689 @@ * 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> #include <linux/sched.h> +#include <linux/sched/task_stack.h> #include <linux/kernel.h> #include <linux/errno.h> #include <linux/string.h> +#include <linux/string_choices.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/module.h> +#include <linux/extable.h> #include <linux/kprobes.h> #include <linux/kdebug.h> #include <linux/perf_event.h> -#include <linux/magic.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/pgtable.h> #include <asm/mmu.h> #include <asm/mmu_context.h> -#include <asm/uaccess.h> -#include <asm/tlbflush.h> #include <asm/siginfo.h> #include <asm/debug.h> -#include <mm/mmu_decl.h> +#include <asm/kup.h> +#include <asm/inst.h> + -#include "icswx.h" +/* + * do_page_fault error handling helpers + */ -#ifdef CONFIG_KPROBES -static inline int notify_page_fault(struct pt_regs *regs) +static int +__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code) { - int ret = 0; + /* + * 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; - /* kprobe_running() needs smp_processor_id() */ - if (!user_mode(regs)) { - preempt_disable(); - if (kprobe_running() && kprobe_fault_handler(regs, 11)) - ret = 1; - preempt_enable(); - } + _exception(SIGSEGV, regs, si_code, address); - return ret; + return 0; } -#else -static inline int notify_page_fault(struct pt_regs *regs) + +static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address) { - return 0; + return __bad_area_nosemaphore(regs, address, SEGV_MAPERR); } -#endif -/* - * Check whether the instruction at regs->nip is a store using - * an update addressing form which will update r1. - */ -static int store_updates_sp(struct pt_regs *regs) +static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code, + struct mm_struct *mm, struct vm_area_struct *vma) { - unsigned int inst; - if (get_user(inst, (unsigned int __user *)regs->nip)) - return 0; - /* check for 1 in the rA field */ - if (((inst >> 16) & 0x1f) != 1) - return 0; - /* check major opcode */ - switch (inst >> 26) { - case 37: /* stwu */ - case 39: /* stbu */ - case 45: /* sthu */ - case 53: /* stfsu */ - case 55: /* stfdu */ - return 1; - case 62: /* std or stdu */ - return (inst & 3) == 1; - case 31: - /* check minor opcode */ - switch ((inst >> 1) & 0x3ff) { - case 181: /* stdux */ - case 183: /* stwux */ - case 247: /* stbux */ - case 439: /* sthux */ - case 695: /* stfsux */ - case 759: /* stfdux */ - return 1; - } - } + /* + * Something tried to access memory that isn't in our memory map.. + * Fix it, but check if it's kernel or user first.. + */ + if (mm) + mmap_read_unlock(mm); + else + vma_end_read(vma); + + return __bad_area_nosemaphore(regs, address, si_code); +} + +static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address, + struct mm_struct *mm, + struct vm_area_struct *vma) +{ + 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); + + if (mm) + mmap_read_unlock(mm); + else + vma_end_read(vma); + + /* + * 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; } -/* - * do_page_fault error handling helpers - */ -#define MM_FAULT_RETURN 0 -#define MM_FAULT_CONTINUE -1 -#define MM_FAULT_ERR(sig) (sig) +static noinline int bad_access(struct pt_regs *regs, unsigned long address, + struct mm_struct *mm, struct vm_area_struct *vma) +{ + return __bad_area(regs, address, SEGV_ACCERR, mm, vma); +} -static int do_sigbus(struct pt_regs *regs, unsigned long address) +static int do_sigbus(struct pt_regs *regs, unsigned long address, + vm_fault_t fault) { - siginfo_t info; - - up_read(¤t->mm->mmap_sem); - - if (user_mode(regs)) { - current->thread.trap_nr = BUS_ADRERR; - info.si_signo = SIGBUS; - info.si_errno = 0; - info.si_code = BUS_ADRERR; - info.si_addr = (void __user *)address; - force_sig_info(SIGBUS, &info, current); - return MM_FAULT_RETURN; + 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; } - return MM_FAULT_ERR(SIGBUS); + +#endif + force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); + return 0; } -static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault) +static int mm_fault_error(struct pt_regs *regs, unsigned long addr, + vm_fault_t fault) { /* - * Pagefault was interrupted by SIGKILL. We have no reason to - * continue the pagefault. + * Kernel page fault interrupted by SIGKILL. We have no reason to + * continue processing. */ - if (fatal_signal_pending(current)) { - /* - * If we have retry set, the mmap semaphore will have - * alrady been released in __lock_page_or_retry(). Else - * we release it now. - */ - if (!(fault & VM_FAULT_RETRY)) - up_read(¤t->mm->mmap_sem); - /* Coming from kernel, we need to deal with uaccess fixups */ - if (user_mode(regs)) - return MM_FAULT_RETURN; - return MM_FAULT_ERR(SIGKILL); - } - - /* No fault: be happy */ - if (!(fault & VM_FAULT_ERROR)) - return MM_FAULT_CONTINUE; + if (fatal_signal_pending(current) && !user_mode(regs)) + return SIGKILL; /* Out of memory */ if (fault & VM_FAULT_OOM) { - up_read(¤t->mm->mmap_sem); - /* * 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 MM_FAULT_ERR(SIGKILL); + return SIGSEGV; pagefault_out_of_memory(); - return MM_FAULT_RETURN; + } 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", + str_write_read(is_write), 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))); } - /* Bus error. x86 handles HWPOISON here, we'll add this if/when - * we support the feature in HW + if (is_write) { + if (unlikely(!(vma->vm_flags & VM_WRITE))) + return true; + return false; + } + + /* + * VM_READ, VM_WRITE and VM_EXEC may imply read permissions, as + * defined in protection_map[]. In that case Read faults can only be + * caused by a PROT_NONE mapping. However a non exec access on a + * VM_EXEC only mapping is invalid anyway, so report it as such. + */ + if (unlikely(!vma_is_accessible(vma))) + return true; + + if ((vma->vm_flags & VM_ACCESS_FLAGS) == VM_EXEC) + 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 + */ +#ifdef CONFIG_BOOKE +#define page_fault_is_write(__err) ((__err) & ESR_DST) +#else +#define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE) +#endif + +#ifdef 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) +static int page_fault_is_bad(unsigned long err) +{ + unsigned long flag = DSISR_BAD_FAULT_64S; + + /* + * PAPR+ v2.11 ยง 14.15.3.4.1 (unreleased) + * If byte 0, bit 3 of pi-attribute-specifier-type in + * ibm,pi-features property is defined, ignore the DSI error + * which is caused by the paste instruction on the + * suspended NX window. */ - if (fault & VM_FAULT_SIGBUS) - return do_sigbus(regs, addr); + if (mmu_has_feature(MMU_FTR_NX_DSI)) + flag &= ~DSISR_BAD_COPYPASTE; - /* We don't understand the fault code, this is fatal */ - BUG(); - return MM_FAULT_CONTINUE; + return err & flag; } +#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 non-SLB data access fault, - * - SRR1 & 0x08000000 for a non-SLB instruction access fault - * - 0 any SLB fault. + * 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. */ -int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, - unsigned long error_code) +static int ___do_page_fault(struct pt_regs *regs, unsigned long address, + unsigned long error_code) { - enum ctx_state prev_state = exception_enter(); struct vm_area_struct * vma; struct mm_struct *mm = current->mm; - unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; - int code = SEGV_MAPERR; - int is_write = 0; - int trap = TRAP(regs); - int is_exec = trap == 0x400; - int fault; - int rc = 0; - -#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) + 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); + /* - * Fortunately the bit assignments in SRR1 for an instruction - * fault and DSISR for a data fault are mostly the same for the - * bits we are interested in. But there are some bits which - * indicate errors in DSISR but can validly be set in SRR1. + * 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. + * + * Rather than kfence directly reporting false negatives, search whether + * the NIP belongs to the fixup table for cases where fault could come + * from functions like copy_from_kernel_nofault(). */ - if (trap == 0x400) - error_code &= 0x48200000; - else - is_write = error_code & DSISR_ISSTORE; -#else - is_write = error_code & ESR_DST; -#endif /* CONFIG_4xx || CONFIG_BOOKE */ + if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write))) { + if (is_kfence_address((void *)address) && + !search_exception_tables(instruction_pointer(regs)) && + kfence_handle_page_fault(address, is_write, regs)) + return 0; - if (is_write) - flags |= FAULT_FLAG_WRITE; + return SIGSEGV; + } -#ifdef CONFIG_PPC_ICSWX /* - * we need to do this early because this "data storage - * interrupt" does not update the DAR/DEAR so we don't want to - * look at it + * 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 (error_code & ICSWX_DSI_UCT) { - rc = acop_handle_fault(regs, address, error_code); - if (rc) - goto bail; + 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); } -#endif /* CONFIG_PPC_ICSWX */ - if (notify_page_fault(regs)) - goto bail; + interrupt_cond_local_irq_enable(regs); + + perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); - if (unlikely(debugger_fault_handler(regs))) - goto bail; + /* + * 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; - /* On a kernel SLB miss we can only check for a valid exception entry */ - if (!user_mode(regs) && (address >= TASK_SIZE)) { - rc = SIGSEGV; - goto bail; + if (!(flags & FAULT_FLAG_USER)) + goto lock_mmap; + + vma = lock_vma_under_rcu(mm, address); + if (!vma) + goto lock_mmap; + + if (unlikely(access_pkey_error(is_write, is_exec, + (error_code & DSISR_KEYFAULT), vma))) { + count_vm_vma_lock_event(VMA_LOCK_SUCCESS); + return bad_access_pkey(regs, address, NULL, vma); } -#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \ - defined(CONFIG_PPC_BOOK3S_64)) - if (error_code & DSISR_DABRMATCH) { - /* breakpoint match */ - do_break(regs, address, error_code); - goto bail; + if (unlikely(access_error(is_write, is_exec, vma))) { + count_vm_vma_lock_event(VMA_LOCK_SUCCESS); + return bad_access(regs, address, NULL, vma); } -#endif - /* We restore the interrupt state now */ - if (!arch_irq_disabled_regs(regs)) - local_irq_enable(); + fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); + if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) + vma_end_read(vma); - if (in_atomic() || mm == NULL) { - if (!user_mode(regs)) { - rc = SIGSEGV; - goto bail; - } - /* in_atomic() in user mode is really bad, - as is current->mm == NULL. */ - printk(KERN_EMERG "Page fault in user mode with " - "in_atomic() = %d mm = %p\n", in_atomic(), mm); - printk(KERN_EMERG "NIP = %lx MSR = %lx\n", - regs->nip, regs->msr); - die("Weird page fault", regs, SIGSEGV); + if (!(fault & VM_FAULT_RETRY)) { + count_vm_vma_lock_event(VMA_LOCK_SUCCESS); + goto done; } + count_vm_vma_lock_event(VMA_LOCK_RETRY); + if (fault & VM_FAULT_MAJOR) + flags |= FAULT_FLAG_TRIED; - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); + if (fault_signal_pending(fault, regs)) + return user_mode(regs) ? 0 : SIGBUS; + +lock_mmap: /* 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_sem + * 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. + * exceptions table. lock_mm_and_find_vma() handles that logic. */ - if (!down_read_trylock(&mm->mmap_sem)) { - if (!user_mode(regs) && !search_exception_tables(regs->nip)) - goto bad_area_nosemaphore; - retry: - down_read(&mm->mmap_sem); - } 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 = lock_mm_and_find_vma(mm, address, regs); + if (unlikely(!vma)) + return bad_area_nosemaphore(regs, address); - vma = find_vma(mm, address); - if (!vma) - goto bad_area; - if (vma->vm_start <= address) - goto good_area; - if (!(vma->vm_flags & VM_GROWSDOWN)) - goto bad_area; + if (unlikely(access_pkey_error(is_write, is_exec, + (error_code & DSISR_KEYFAULT), vma))) + return bad_access_pkey(regs, address, mm, vma); - /* - * N.B. The POWER/Open ABI allows programs to access up to - * 288 bytes below the stack pointer. - * The kernel signal delivery code writes up to about 1.5kB - * below the stack pointer (r1) before decrementing it. - * The exec code can write slightly over 640kB to the stack - * before setting the user r1. Thus we allow the stack to - * expand to 1MB without further checks. - */ - if (address + 0x100000 < vma->vm_end) { - /* get user regs even if this fault is in kernel mode */ - struct pt_regs *uregs = current->thread.regs; - if (uregs == NULL) - goto bad_area; - - /* - * A user-mode access to an address a long way below - * the stack pointer is only valid if the instruction - * is one which would update the stack pointer to the - * address accessed if the instruction completed, - * i.e. either stwu rs,n(r1) or stwux rs,r1,rb - * (or the byte, halfword, float or double forms). - * - * If we don't check this then any write to the area - * between the last mapped region and the stack will - * expand the stack rather than segfaulting. - */ - if (address + 2048 < uregs->gpr[1] - && (!user_mode(regs) || !store_updates_sp(regs))) - goto bad_area; - } - if (expand_stack(vma, address)) - goto bad_area; - -good_area: - code = SEGV_ACCERR; -#if defined(CONFIG_6xx) - if (error_code & 0x95700000) - /* an error such as lwarx to I/O controller space, - address matching DABR, eciwx, etc. */ - goto bad_area; -#endif /* CONFIG_6xx */ -#if defined(CONFIG_8xx) - /* 8xx sometimes need to load a invalid/non-present TLBs. - * These must be invalidated separately as linux mm don't. - */ - if (error_code & 0x40000000) /* no translation? */ - _tlbil_va(address, 0, 0, 0); - - /* The MPC8xx seems to always set 0x80000000, which is - * "undefined". Of those that can be set, this is the only - * one which seems bad. - */ - if (error_code & 0x10000000) - /* Guarded storage error. */ - goto bad_area; -#endif /* CONFIG_8xx */ - - if (is_exec) { -#ifdef CONFIG_PPC_STD_MMU - /* Protection fault on exec go straight to failure on - * Hash based MMUs as they either don't support per-page - * execute permission, or if they do, it's handled already - * at the hash level. This test would probably have to - * be removed if we change the way this works to make hash - * processors use the same I/D cache coherency mechanism - * as embedded. - */ - if (error_code & DSISR_PROTFAULT) - goto bad_area; -#endif /* CONFIG_PPC_STD_MMU */ - - /* - * 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 (!(vma->vm_flags & VM_EXEC) && - (cpu_has_feature(CPU_FTR_NOEXECUTE) || - !(vma->vm_flags & (VM_READ | VM_WRITE)))) - goto bad_area; - /* a write */ - } else if (is_write) { - if (!(vma->vm_flags & VM_WRITE)) - goto bad_area; - /* a read */ - } else { - /* protection fault */ - if (error_code & 0x08000000) - goto bad_area; - if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) - goto bad_area; - } + if (unlikely(access_error(is_write, is_exec, vma))) + return bad_access(regs, address, mm, vma); /* * 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(mm, vma, address, flags); - if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) { - rc = mm_fault_error(regs, address, fault); - if (rc >= MM_FAULT_RETURN) - goto bail; - else - rc = 0; - } + 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; /* - * Major/minor page fault accounting is only done on the - * initial attempt. If we go through a retry, it is extremely - * likely that the page will be found in page cache at that point. + * Handle the retry right now, the mmap_lock has been released in that + * case. */ - if (flags & FAULT_FLAG_ALLOW_RETRY) { - if (fault & VM_FAULT_MAJOR) { - current->maj_flt++; - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, - regs, address); -#ifdef CONFIG_PPC_SMLPAR - if (firmware_has_feature(FW_FEATURE_CMO)) { - preempt_disable(); - get_lppaca()->page_ins += (1 << PAGE_FACTOR); - preempt_enable(); - } -#endif /* CONFIG_PPC_SMLPAR */ - } else { - current->min_flt++; - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, - regs, address); - } - if (fault & VM_FAULT_RETRY) { - /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk - * of starvation. */ - flags &= ~FAULT_FLAG_ALLOW_RETRY; - flags |= FAULT_FLAG_TRIED; - goto retry; - } + if (unlikely(fault & VM_FAULT_RETRY)) { + flags |= FAULT_FLAG_TRIED; + goto retry; } - up_read(&mm->mmap_sem); - goto bail; + mmap_read_unlock(current->mm); -bad_area: - up_read(&mm->mmap_sem); +done: + if (unlikely(fault & VM_FAULT_ERROR)) + return mm_fault_error(regs, address, fault); -bad_area_nosemaphore: - /* User mode accesses cause a SIGSEGV */ - if (user_mode(regs)) { - _exception(SIGSEGV, regs, code, address); - goto bail; - } +out: + /* + * Major/minor page fault accounting. + */ + if (major) + cmo_account_page_fault(); - if (is_exec && (error_code & DSISR_PROTFAULT)) - printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected" - " page (%lx) - exploit attempt? (uid: %d)\n", - address, from_kuid(&init_user_ns, current_uid())); + return 0; +} +NOKPROBE_SYMBOL(___do_page_fault); - rc = SIGSEGV; +static __always_inline void __do_page_fault(struct pt_regs *regs) +{ + long err; -bail: - exception_exit(prev_state); - return rc; + 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. */ -void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) +static void __bad_page_fault(struct pt_regs *regs, int sig) { - const struct exception_table_entry *entry; - unsigned long *stackend; - - /* Are we prepared to handle this fault? */ - if ((entry = search_exception_tables(regs->nip)) != NULL) { - regs->nip = entry->fixup; - return; - } + int is_write = page_fault_is_write(regs->dsisr); + const char *msg; /* kernel has accessed a bad area */ - switch (regs->trap) { - case 0x300: - case 0x380: - printk(KERN_ALERT "Unable to handle kernel paging request for " - "data at address 0x%08lx\n", regs->dar); + 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, + str_write_read(is_write), regs->dar); + break; + case INTERRUPT_DATA_SEGMENT: + pr_alert("BUG: %s at 0x%08lx\n", msg, regs->dar); break; - case 0x400: - case 0x480: - printk(KERN_ALERT "Unable to handle kernel paging request for " - "instruction fetch\n"); + 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: - printk(KERN_ALERT "Unable to handle kernel paging request for " - "unknown fault\n"); + 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); - stackend = end_of_stack(current); - if (current != &init_task && *stackend != STACK_END_MAGIC) + 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 |