Commit message: x86/dumpstack: Don't dump kernel memory based on usermode RIP


show_opcodes() is used both for dumping kernel instructions and for dumping
user instructions. If userspace causes #PF by jumping to a kernel address,
show_opcodes() can be reached with regs->ip controlled by the user,
pointing to kernel code. Make sure that userspace can't trick us into
dumping kernel memory into dmesg.

Fixes: 7cccf0725cf7 ("x86/dumpstack: Add a show_ip() function")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: security@kernel.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180828154901.112726-1-jannh@google.com
CVE: CVE-2018-14656
CWE: CWE-20
Vulnerability description: A missing address check in the callers of the show_opcodes() in the Linux kernel allows an attacker to dump the kernel memory at an arbitrary kernel address into the dmesg log.

Project: linux
File: fault.c

do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
	  u32 *pkey, unsigned int fault)
{
	struct task_struct *tsk = current;
	int code = BUS_ADRERR;

	/* Kernel mode? Handle exceptions or die: */
	if (!(error_code & X86_PF_USER)) {
		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
		return;
	}

	/* User-space => ok to do another page fault: */
	if (is_prefetch(regs, error_code, address))
		return;

	tsk->thread.cr2		= address;
	tsk->thread.error_code	= error_code;
	tsk->thread.trap_nr	= X86_TRAP_PF;

#ifdef CONFIG_MEMORY_FAILURE
	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
		printk(KERN_ERR
	"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
			tsk->comm, tsk->pid, address);
		code = BUS_MCEERR_AR;
	}
#endif
	force_sig_info_fault(SIGBUS, code, address, tsk, pkey, fault);
}

Project: linux
File: dumpstack.c

bool in_task_stack(unsigned long *stack, struct task_struct *task,
		   struct stack_info *info)
{
	unsigned long *begin = task_stack_page(task);
	unsigned long *end   = task_stack_page(task) + THREAD_SIZE;

	if (stack < begin || stack >= end)
		return false;

	info->type	= STACK_TYPE_TASK;
	info->begin	= begin;
	info->end	= end;
	info->next_sp	= NULL;

	return true;
}

Project: linux
File: fault.c

static int spurious_fault_check(unsigned long error_code, pte_t *pte)
{
	if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
		return 0;

	if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
		return 0;
	/*
	 * Note: We do not do lazy flushing on protection key
	 * changes, so no spurious fault will ever set X86_PF_PK.
	 */
	if ((error_code & X86_PF_PK))
		return 1;

	return 1;
}

Project: linux
File: dumpstack.c

void show_ip(struct pt_regs *regs, const char *loglvl)
{
#ifdef CONFIG_X86_32
	printk("%sEIP: %pS\n", loglvl, (void *)regs->ip);
#else
	printk("%sRIP: %04x:%pS\n", loglvl, (int)regs->cs, (void *)regs->ip);
#endif
	show_opcodes(regs, loglvl);
}

Project: linux
File: fault.c

show_signal_msg(struct pt_regs *regs, unsigned long error_code,
		unsigned long address, struct task_struct *tsk)
{
	const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;

	if (!unhandled_signal(tsk, SIGSEGV))
		return;

	if (!printk_ratelimit())
		return;

	printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
		loglvl, tsk->comm, task_pid_nr(tsk), address,
		(void *)regs->ip, (void *)regs->sp, error_code);

	print_vma_addr(KERN_CONT " in ", regs->ip);

	printk(KERN_CONT "\n");

	show_opcodes(regs, loglvl);
}

Project: linux
File: fault.c

__bad_area(struct pt_regs *regs, unsigned long error_code,
	   unsigned long address,  struct vm_area_struct *vma, int si_code)
{
	struct mm_struct *mm = current->mm;
	u32 pkey;

	if (vma)
		pkey = vma_pkey(vma);

	/*
	 * Something tried to access memory that isn't in our memory map..
	 * Fix it, but check if it's kernel or user first..
	 */
	up_read(&mm->mmap_sem);

	__bad_area_nosemaphore(regs, error_code, address,
			       (vma) ? &pkey : NULL, si_code);
}

Project: linux
File: fault.c

static void dump_pagetable(unsigned long address)
{
	pgd_t *base = __va(read_cr3_pa());
	pgd_t *pgd = &base[pgd_index(address)];
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

#ifdef CONFIG_X86_PAE
	pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
	if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
		goto out;
#define pr_pde pr_cont
#else
#define pr_pde pr_info
#endif
	p4d = p4d_offset(pgd, address);
	pud = pud_offset(p4d, address);
	pmd = pmd_offset(pud, address);
	pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
#undef pr_pde

	/*
	 * We must not directly access the pte in the highpte
	 * case if the page table is located in highmem.
	 * And let's rather not kmap-atomic the pte, just in case
	 * it's allocated already:
	 */
	if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
		goto out;

	pte = pte_offset_kernel(pmd, address);
	pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
out:
	pr_cont("\n");
}

Project: linux
File: dumpstack.c

void show_stack(struct task_struct *task, unsigned long *sp)
{
	task = task ? : current;

	/*
	 * Stack frames below this one aren't interesting.  Don't show them
	 * if we're printing for %current.
	 */
	if (!sp && task == current)
		sp = get_stack_pointer(current, NULL);

	show_trace_log_lvl(task, NULL, sp, KERN_DEFAULT);
}

Project: linux
File: fault.c

static noinline int vmalloc_fault(unsigned long address)
{
	pgd_t *pgd, *pgd_k;
	p4d_t *p4d, *p4d_k;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	/* Make sure we are in vmalloc area: */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

	WARN_ON_ONCE(in_nmi());

	/*
	 * Copy kernel mappings over when needed. This can also
	 * happen within a race in page table update. In the later
	 * case just flush:
	 */
	pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address);
	pgd_k = pgd_offset_k(address);
	if (pgd_none(*pgd_k))
		return -1;

	if (pgtable_l5_enabled()) {
		if (pgd_none(*pgd)) {
			set_pgd(pgd, *pgd_k);
			arch_flush_lazy_mmu_mode();
		} else {
			BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k));
		}
	}

	/* With 4-level paging, copying happens on the p4d level. */
	p4d = p4d_offset(pgd, address);
	p4d_k = p4d_offset(pgd_k, address);
	if (p4d_none(*p4d_k))
		return -1;

	if (p4d_none(*p4d) && !pgtable_l5_enabled()) {
		set_p4d(p4d, *p4d_k);
		arch_flush_lazy_mmu_mode();
	} else {
		BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_k));
	}

	BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4);

	pud = pud_offset(p4d, address);
	if (pud_none(*pud))
		return -1;

	if (pud_large(*pud))
		return 0;

	pmd = pmd_offset(pud, address);
	if (pmd_none(*pmd))
		return -1;

	if (pmd_large(*pmd))
		return 0;

	pte = pte_offset_kernel(pmd, address);
	if (!pte_present(*pte))
		return -1;

	return 0;
}

Project: linux
File: fault.c

bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
	__bad_area(regs, error_code, address, NULL, SEGV_MAPERR);
}

Project: linux
File: fault.c

static inline bool bad_area_access_from_pkeys(unsigned long error_code,
		struct vm_area_struct *vma)
{
	/* This code is always called on the current mm */
	bool foreign = false;

	if (!boot_cpu_has(X86_FEATURE_OSPKE))
		return false;
	if (error_code & X86_PF_PK)
		return true;
	/* this checks permission keys on the VMA: */
	if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
				       (error_code & X86_PF_INSTR), foreign))
		return true;
	return false;
}

Project: linux
File: fault.c

static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
{
	unsigned index = pgd_index(address);
	pgd_t *pgd_k;
	p4d_t *p4d, *p4d_k;
	pud_t *pud, *pud_k;
	pmd_t *pmd, *pmd_k;

	pgd += index;
	pgd_k = init_mm.pgd + index;

	if (!pgd_present(*pgd_k))
		return NULL;

	/*
	 * set_pgd(pgd, *pgd_k); here would be useless on PAE
	 * and redundant with the set_pmd() on non-PAE. As would
	 * set_p4d/set_pud.
	 */
	p4d = p4d_offset(pgd, address);
	p4d_k = p4d_offset(pgd_k, address);
	if (!p4d_present(*p4d_k))
		return NULL;

	pud = pud_offset(p4d, address);
	pud_k = pud_offset(p4d_k, address);
	if (!pud_present(*pud_k))
		return NULL;

	pmd = pmd_offset(pud, address);
	pmd_k = pmd_offset(pud_k, address);
	if (!pmd_present(*pmd_k))
		return NULL;

	if (!pmd_present(*pmd))
		set_pmd(pmd, *pmd_k);
	else
		BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));

	return pmd_k;
}

Project: linux
File: fault.c

bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
		     unsigned long address, u32 *pkey)
{
	__bad_area_nosemaphore(regs, error_code, address, pkey, SEGV_MAPERR);
}

Project: linux
File: fault.c

void vmalloc_sync_all(void)
{
	unsigned long address;

	if (SHARED_KERNEL_PMD)
		return;

	for (address = VMALLOC_START & PMD_MASK;
	     address >= TASK_SIZE_MAX && address < FIXADDR_TOP;
	     address += PMD_SIZE) {
		struct page *page;

		spin_lock(&pgd_lock);
		list_for_each_entry(page, &pgd_list, lru) {
			spinlock_t *pgt_lock;
			pmd_t *ret;

			/* the pgt_lock only for Xen */
			pgt_lock = &pgd_page_get_mm(page)->page_table_lock;

			spin_lock(pgt_lock);
			ret = vmalloc_sync_one(page_address(page), address);
			spin_unlock(pgt_lock);

			if (!ret)
				break;
		}
		spin_unlock(&pgd_lock);
	}
}

Project: linux
File: dumpstack.c

bool in_entry_stack(unsigned long *stack, struct stack_info *info)
{
	struct entry_stack *ss = cpu_entry_stack(smp_processor_id());

	void *begin = ss;
	void *end = ss + 1;

	if ((void *)stack < begin || (void *)stack >= end)
		return false;

	info->type	= STACK_TYPE_ENTRY;
	info->begin	= begin;
	info->end	= end;
	info->next_sp	= NULL;

	return true;
}

Project: linux
File: dumpstack.c

void show_opcodes(struct pt_regs *regs, const char *loglvl)
{
#define PROLOGUE_SIZE 42
#define EPILOGUE_SIZE 21
#define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE)
	u8 opcodes[OPCODE_BUFSIZE];
	unsigned long prologue = regs->ip - PROLOGUE_SIZE;
	bool bad_ip;

	/*
	 * Make sure userspace isn't trying to trick us into dumping kernel
	 * memory by pointing the userspace instruction pointer at it.
	 */
	bad_ip = user_mode(regs) &&
		__chk_range_not_ok(prologue, OPCODE_BUFSIZE, TASK_SIZE_MAX);

	if (bad_ip || probe_kernel_read(opcodes, (u8 *)prologue,
					OPCODE_BUFSIZE)) {
		printk("%sCode: Bad RIP value.\n", loglvl);
	} else {
		printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %"
		       __stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes,
		       opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1);
	}
}

Project: linux
File: fault.c

static noinline int vmalloc_fault(unsigned long address)
{
	unsigned long pgd_paddr;
	pmd_t *pmd_k;
	pte_t *pte_k;

	/* Make sure we are in vmalloc area: */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

	/*
	 * Synchronize this task's top level page-table
	 * with the 'reference' page table.
	 *
	 * Do _not_ use "current" here. We might be inside
	 * an interrupt in the middle of a task switch..
	 */
	pgd_paddr = read_cr3_pa();
	pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
	if (!pmd_k)
		return -1;

	if (pmd_large(*pmd_k))
		return 0;

	pte_k = pte_offset_kernel(pmd_k, address);
	if (!pte_present(*pte_k))
		return -1;

	return 0;
}

Project: linux
File: dumpstack.c

void show_iret_regs(struct pt_regs *regs)
{
	show_ip(regs, KERN_DEFAULT);
	printk(KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx", (int)regs->ss,
		regs->sp, regs->flags);
}

Project: linux
File: fault.c

show_fault_oops(struct pt_regs *regs, unsigned long error_code,
		unsigned long address)
{
	if (!oops_may_print())
		return;

	if (error_code & X86_PF_INSTR) {
		unsigned int level;
		pgd_t *pgd;
		pte_t *pte;

		pgd = __va(read_cr3_pa());
		pgd += pgd_index(address);

		pte = lookup_address_in_pgd(pgd, address, &level);

		if (pte && pte_present(*pte) && !pte_exec(*pte))
			pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
				from_kuid(&init_user_ns, current_uid()));
		if (pte && pte_present(*pte) && pte_exec(*pte) &&
				(pgd_flags(*pgd) & _PAGE_USER) &&
				(__read_cr4() & X86_CR4_SMEP))
			pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
				from_kuid(&init_user_ns, current_uid()));
	}

	pr_alert("BUG: unable to handle kernel %s at %px\n",
		 address < PAGE_SIZE ? "NULL pointer dereference" : "paging request",
		 (void *)address);

	dump_pagetable(address);
}

Project: linux
File: fault.c

static void fill_sig_info_pkey(int si_signo, int si_code, siginfo_t *info,
		u32 *pkey)
{
	/* This is effectively an #ifdef */
	if (!boot_cpu_has(X86_FEATURE_OSPKE))
		return;

	/* Fault not from Protection Keys: nothing to do */
	if ((si_code != SEGV_PKUERR) || (si_signo != SIGSEGV))
		return;
	/*
	 * force_sig_info_fault() is called from a number of
	 * contexts, some of which have a VMA and some of which
	 * do not.  The X86_PF_PK handing happens after we have a
	 * valid VMA, so we should never reach this without a
	 * valid VMA.
	 */
	if (!pkey) {
		WARN_ONCE(1, "PKU fault with no VMA passed in");
		info->si_pkey = 0;
		return;
	}
	/*
	 * si_pkey should be thought of as a strong hint, but not
	 * absolutely guranteed to be 100% accurate because of
	 * the race explained above.
	 */
	info->si_pkey = *pkey;
}

Project: linux
File: fault.c

access_error(unsigned long error_code, struct vm_area_struct *vma)
{
	/* This is only called for the current mm, so: */
	bool foreign = false;

	/*
	 * Read or write was blocked by protection keys.  This is
	 * always an unconditional error and can never result in
	 * a follow-up action to resolve the fault, like a COW.
	 */
	if (error_code & X86_PF_PK)
		return 1;

	/*
	 * Make sure to check the VMA so that we do not perform
	 * faults just to hit a X86_PF_PK as soon as we fill in a
	 * page.
	 */
	if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
				       (error_code & X86_PF_INSTR), foreign))
		return 1;

	if (error_code & X86_PF_WRITE) {
		/* write, present and write, not present: */
		if (unlikely(!(vma->vm_flags & VM_WRITE)))
			return 1;
		return 0;
	}

	/* read, present: */
	if (unlikely(error_code & X86_PF_PROT))
		return 1;

	/* read, not present: */
	if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
		return 1;

	return 0;
}

Project: linux
File: fault.c

is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
{
	unsigned char *max_instr;
	unsigned char *instr;
	int prefetch = 0;

	/*
	 * If it was a exec (instruction fetch) fault on NX page, then
	 * do not ignore the fault:
	 */
	if (error_code & X86_PF_INSTR)
		return 0;

	instr = (void *)convert_ip_to_linear(current, regs);
	max_instr = instr + 15;

	if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
		return 0;

	while (instr < max_instr) {
		unsigned char opcode;

		if (probe_kernel_address(instr, opcode))
			break;

		instr++;

		if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
			break;
	}
	return prefetch;
}

Project: linux
File: dumpstack.c

unsigned long oops_begin(void)
{
	int cpu;
	unsigned long flags;

	oops_enter();

	/* racy, but better than risking deadlock. */
	raw_local_irq_save(flags);
	cpu = smp_processor_id();
	if (!arch_spin_trylock(&die_lock)) {
		if (cpu == die_owner)
			/* nested oops. should stop eventually */;
		else
			arch_spin_lock(&die_lock);
	}
	die_nest_count++;
	die_owner = cpu;
	console_verbose();
	bust_spinlocks(1);
	return flags;
}

Project: linux
File: fault.c

mm_fault_error(struct pt_regs *regs, unsigned long error_code,
	       unsigned long address, u32 *pkey, vm_fault_t fault)
{
	if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
		no_context(regs, error_code, address, 0, 0);
		return;
	}

	if (fault & VM_FAULT_OOM) {
		/* Kernel mode? Handle exceptions or die: */
		if (!(error_code & X86_PF_USER)) {
			no_context(regs, error_code, address,
				   SIGSEGV, SEGV_MAPERR);
			return;
		}

		/*
		 * We ran out of memory, call the OOM killer, and return the
		 * userspace (which will retry the fault, or kill us if we got
		 * oom-killed):
		 */
		pagefault_out_of_memory();
	} else {
		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
			     VM_FAULT_HWPOISON_LARGE))
			do_sigbus(regs, error_code, address, pkey, fault);
		else if (fault & VM_FAULT_SIGSEGV)
			bad_area_nosemaphore(regs, error_code, address, pkey);
		else
			BUG();
	}
}

Project: linux
File: dumpstack.c

void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
			unsigned long *stack, char *log_lvl)
{
	struct unwind_state state;
	struct stack_info stack_info = {0};
	unsigned long visit_mask = 0;
	int graph_idx = 0;
	bool partial = false;

	printk("%sCall Trace:\n", log_lvl);

	unwind_start(&state, task, regs, stack);
	stack = stack ? : get_stack_pointer(task, regs);
	regs = unwind_get_entry_regs(&state, &partial);

	/*
	 * Iterate through the stacks, starting with the current stack pointer.
	 * Each stack has a pointer to the next one.
	 *
	 * x86-64 can have several stacks:
	 * - task stack
	 * - interrupt stack
	 * - HW exception stacks (double fault, nmi, debug, mce)
	 * - entry stack
	 *
	 * x86-32 can have up to four stacks:
	 * - task stack
	 * - softirq stack
	 * - hardirq stack
	 * - entry stack
	 */
	for ( ; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
		const char *stack_name;

		if (get_stack_info(stack, task, &stack_info, &visit_mask)) {
			/*
			 * We weren't on a valid stack.  It's possible that
			 * we overflowed a valid stack into a guard page.
			 * See if the next page up is valid so that we can
			 * generate some kind of backtrace if this happens.
			 */
			stack = (unsigned long *)PAGE_ALIGN((unsigned long)stack);
			if (get_stack_info(stack, task, &stack_info, &visit_mask))
				break;
		}

		stack_name = stack_type_name(stack_info.type);
		if (stack_name)
			printk("%s <%s>\n", log_lvl, stack_name);

		if (regs)
			show_regs_if_on_stack(&stack_info, regs, partial);

		/*
		 * Scan the stack, printing any text addresses we find.  At the
		 * same time, follow proper stack frames with the unwinder.
		 *
		 * Addresses found during the scan which are not reported by
		 * the unwinder are considered to be additional clues which are
		 * sometimes useful for debugging and are prefixed with '?'.
		 * This also serves as a failsafe option in case the unwinder
		 * goes off in the weeds.
		 */
		for (; stack < stack_info.end; stack++) {
			unsigned long real_addr;
			int reliable = 0;
			unsigned long addr = READ_ONCE_NOCHECK(*stack);
			unsigned long *ret_addr_p =
				unwind_get_return_address_ptr(&state);

			if (!__kernel_text_address(addr))
				continue;

			/*
			 * Don't print regs->ip again if it was already printed
			 * by show_regs_if_on_stack().
			 */
			if (regs && stack == &regs->ip)
				goto next;

			if (stack == ret_addr_p)
				reliable = 1;

			/*
			 * When function graph tracing is enabled for a
			 * function, its return address on the stack is
			 * replaced with the address of an ftrace handler
			 * (return_to_handler).  In that case, before printing
			 * the "real" address, we want to print the handler
			 * address as an "unreliable" hint that function graph
			 * tracing was involved.
			 */
			real_addr = ftrace_graph_ret_addr(task, &graph_idx,
							  addr, stack);
			if (real_addr != addr)
				printk_stack_address(addr, 0, log_lvl);
			printk_stack_address(real_addr, reliable, log_lvl);

			if (!reliable)
				continue;

next:
			/*
			 * Get the next frame from the unwinder.  No need to
			 * check for an error: if anything goes wrong, the rest
			 * of the addresses will just be printed as unreliable.
			 */
			unwind_next_frame(&state);

			/* if the frame has entry regs, print them */
			regs = unwind_get_entry_regs(&state, &partial);
			if (regs)
				show_regs_if_on_stack(&stack_info, regs, partial);
		}

		if (stack_name)
			printk("%s </%s>\n", log_lvl, stack_name);
	}
}

Project: linux
File: dumpstack.c

void die(const char *str, struct pt_regs *regs, long err)
{
	unsigned long flags = oops_begin();
	int sig = SIGSEGV;

	if (__die(str, regs, err))
		sig = 0;
	oops_end(flags, regs, sig);
}

Project: linux
File: fault.c

force_sig_info_fault(int si_signo, int si_code, unsigned long address,
		     struct task_struct *tsk, u32 *pkey, int fault)
{
	unsigned lsb = 0;
	siginfo_t info;

	clear_siginfo(&info);
	info.si_signo	= si_signo;
	info.si_errno	= 0;
	info.si_code	= si_code;
	info.si_addr	= (void __user *)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;
	info.si_addr_lsb = lsb;

	fill_sig_info_pkey(si_signo, si_code, &info, pkey);

	force_sig_info(si_signo, &info, tsk);
}

Project: linux
File: fault.c

no_context(struct pt_regs *regs, unsigned long error_code,
	   unsigned long address, int signal, int si_code)
{
	struct task_struct *tsk = current;
	unsigned long flags;
	int sig;

	/* Are we prepared to handle this kernel fault? */
	if (fixup_exception(regs, X86_TRAP_PF)) {
		/*
		 * Any interrupt that takes a fault gets the fixup. This makes
		 * the below recursive fault logic only apply to a faults from
		 * task context.
		 */
		if (in_interrupt())
			return;

		/*
		 * Per the above we're !in_interrupt(), aka. task context.
		 *
		 * In this case we need to make sure we're not recursively
		 * faulting through the emulate_vsyscall() logic.
		 */
		if (current->thread.sig_on_uaccess_err && signal) {
			tsk->thread.trap_nr = X86_TRAP_PF;
			tsk->thread.error_code = error_code | X86_PF_USER;
			tsk->thread.cr2 = address;

			/* XXX: hwpoison faults will set the wrong code. */
			force_sig_info_fault(signal, si_code, address,
					     tsk, NULL, 0);
		}

		/*
		 * Barring that, we can do the fixup and be happy.
		 */
		return;
	}

#ifdef CONFIG_VMAP_STACK
	/*
	 * Stack overflow?  During boot, we can fault near the initial
	 * stack in the direct map, but that's not an overflow -- check
	 * that we're in vmalloc space to avoid this.
	 */
	if (is_vmalloc_addr((void *)address) &&
	    (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
	     address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
		unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *);
		/*
		 * We're likely to be running with very little stack space
		 * left.  It's plausible that we'd hit this condition but
		 * double-fault even before we get this far, in which case
		 * we're fine: the double-fault handler will deal with it.
		 *
		 * We don't want to make it all the way into the oops code
		 * and then double-fault, though, because we're likely to
		 * break the console driver and lose most of the stack dump.
		 */
		asm volatile ("movq %[stack], %%rsp\n\t"
			      "call handle_stack_overflow\n\t"
			      "1: jmp 1b"
			      : ASM_CALL_CONSTRAINT
			      : "D" ("kernel stack overflow (page fault)"),
				"S" (regs), "d" (address),
				[stack] "rm" (stack));
		unreachable();
	}
#endif

	/*
	 * 32-bit:
	 *
	 *   Valid to do another page fault here, because if this fault
	 *   had been triggered by is_prefetch fixup_exception would have
	 *   handled it.
	 *
	 * 64-bit:
	 *
	 *   Hall of shame of CPU/BIOS bugs.
	 */
	if (is_prefetch(regs, error_code, address))
		return;

	if (is_errata93(regs, address))
		return;

	/*
	 * Oops. The kernel tried to access some bad page. We'll have to
	 * terminate things with extreme prejudice:
	 */
	flags = oops_begin();

	show_fault_oops(regs, error_code, address);

	if (task_stack_end_corrupted(tsk))
		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");

	tsk->thread.cr2		= address;
	tsk->thread.trap_nr	= X86_TRAP_PF;
	tsk->thread.error_code	= error_code;

	sig = SIGKILL;
	if (__die("Oops", regs, error_code))
		sig = 0;

	/* Executive summary in case the body of the oops scrolled away */
	printk(KERN_DEFAULT "CR2: %016lx\n", address);

	oops_end(flags, regs, sig);
}

Project: linux
File: fault.c

static inline bool smap_violation(int error_code, struct pt_regs *regs)
{
	if (!IS_ENABLED(CONFIG_X86_SMAP))
		return false;

	if (!static_cpu_has(X86_FEATURE_SMAP))
		return false;

	if (error_code & X86_PF_USER)
		return false;

	if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
		return false;

	return true;
}

Project: linux
File: dumpstack.c

void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
{
	if (regs && kexec_should_crash(current))
		crash_kexec(regs);

	bust_spinlocks(0);
	die_owner = -1;
	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
	die_nest_count--;
	if (!die_nest_count)
		/* Nest count reaches zero, release the lock. */
		arch_spin_unlock(&die_lock);
	raw_local_irq_restore(flags);
	oops_exit();

	/* Executive summary in case the oops scrolled away */
	__show_regs(&exec_summary_regs, true);

	if (!signr)
		return;
	if (in_interrupt())
		panic("Fatal exception in interrupt");
	if (panic_on_oops)
		panic("Fatal exception");

	/*
	 * We're not going to return, but we might be on an IST stack or
	 * have very little stack space left.  Rewind the stack and kill
	 * the task.
	 * Before we rewind the stack, we have to tell KASAN that we're going to
	 * reuse the task stack and that existing poisons are invalid.
	 */
	kasan_unpoison_task_stack(current);
	rewind_stack_do_exit(signr);
}

Project: linux
File: fault.c

__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
		       unsigned long address, u32 *pkey, int si_code)
{
	struct task_struct *tsk = current;

	/* User mode accesses just cause a SIGSEGV */
	if (error_code & X86_PF_USER) {
		/*
		 * It's possible to have interrupts off here:
		 */
		local_irq_enable();

		/*
		 * Valid to do another page fault here because this one came
		 * from user space:
		 */
		if (is_prefetch(regs, error_code, address))
			return;

		if (is_errata100(regs, address))
			return;

#ifdef CONFIG_X86_64
		/*
		 * Instruction fetch faults in the vsyscall page might need
		 * emulation.
		 */
		if (unlikely((error_code & X86_PF_INSTR) &&
			     ((address & ~0xfff) == VSYSCALL_ADDR))) {
			if (emulate_vsyscall(regs, address))
				return;
		}
#endif

		/*
		 * To avoid leaking information about the kernel page table
		 * layout, pretend that user-mode accesses to kernel addresses
		 * are always protection faults.
		 */
		if (address >= TASK_SIZE_MAX)
			error_code |= X86_PF_PROT;

		if (likely(show_unhandled_signals))
			show_signal_msg(regs, error_code, address, tsk);

		tsk->thread.cr2		= address;
		tsk->thread.error_code	= error_code;
		tsk->thread.trap_nr	= X86_TRAP_PF;

		force_sig_info_fault(SIGSEGV, si_code, address, tsk, pkey, 0);

		return;
	}

	if (is_f00f_bug(regs, address))
		return;

	no_context(regs, error_code, address, SIGSEGV, si_code);
}

Project: linux
File: fault.c

bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
		      unsigned long address, struct vm_area_struct *vma)
{
	/*
	 * This OSPKE check is not strictly necessary at runtime.
	 * But, doing it this way allows compiler optimizations
	 * if pkeys are compiled out.
	 */
	if (bad_area_access_from_pkeys(error_code, vma))
		__bad_area(regs, error_code, address, vma, SEGV_PKUERR);
	else
		__bad_area(regs, error_code, address, vma, SEGV_ACCERR);
}

Project: linux
File: fault.c

do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
	unsigned long address = read_cr2(); /* Get the faulting address */
	enum ctx_state prev_state;

	prev_state = exception_enter();
	if (trace_pagefault_enabled())
		trace_page_fault_entries(address, regs, error_code);

	__do_page_fault(regs, error_code, address);
	exception_exit(prev_state);
}

Project: linux
File: fault.c

spurious_fault(unsigned long error_code, unsigned long address)
{
	pgd_t *pgd;
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	int ret;

	/*
	 * Only writes to RO or instruction fetches from NX may cause
	 * spurious faults.
	 *
	 * These could be from user or supervisor accesses but the TLB
	 * is only lazily flushed after a kernel mapping protection
	 * change, so user accesses are not expected to cause spurious
	 * faults.
	 */
	if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
	    error_code != (X86_PF_INSTR | X86_PF_PROT))
		return 0;

	pgd = init_mm.pgd + pgd_index(address);
	if (!pgd_present(*pgd))
		return 0;

	p4d = p4d_offset(pgd, address);
	if (!p4d_present(*p4d))
		return 0;

	if (p4d_large(*p4d))
		return spurious_fault_check(error_code, (pte_t *) p4d);

	pud = pud_offset(p4d, address);
	if (!pud_present(*pud))
		return 0;

	if (pud_large(*pud))
		return spurious_fault_check(error_code, (pte_t *) pud);

	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		return 0;

	if (pmd_large(*pmd))
		return spurious_fault_check(error_code, (pte_t *) pmd);

	pte = pte_offset_kernel(pmd, address);
	if (!pte_present(*pte))
		return 0;

	ret = spurious_fault_check(error_code, pte);
	if (!ret)
		return 0;

	/*
	 * Make sure we have permissions in PMD.
	 * If not, then there's a bug in the page tables:
	 */
	ret = spurious_fault_check(error_code, (pte_t *) pmd);
	WARN_ONCE(!ret, "PMD has incorrect permission bits\n");

	return ret;
}

Project: linux
File: dumpstack.c

static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
				  bool partial)
{
	/*
	 * These on_stack() checks aren't strictly necessary: the unwind code
	 * has already validated the 'regs' pointer.  The checks are done for
	 * ordering reasons: if the registers are on the next stack, we don't
	 * want to print them out yet.  Otherwise they'll be shown as part of
	 * the wrong stack.  Later, when show_trace_log_lvl() switches to the
	 * next stack, this function will be called again with the same regs so
	 * they can be printed in the right context.
	 */
	if (!partial && on_stack(info, regs, sizeof(*regs))) {
		__show_regs(regs, 0);

	} else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
				       IRET_FRAME_SIZE)) {
		/*
		 * When an interrupt or exception occurs in entry code, the
		 * full pt_regs might not have been saved yet.  In that case
		 * just print the iret frame.
		 */
		show_iret_regs(regs);
	}
}

Project: linux
File: dumpstack.c

static void printk_stack_address(unsigned long address, int reliable,
				 char *log_lvl)
{
	touch_nmi_watchdog();
	printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address);
}

Project: linux
File: dumpstack.c

void show_regs(struct pt_regs *regs)
{
	bool all = true;

	show_regs_print_info(KERN_DEFAULT);

	if (IS_ENABLED(CONFIG_X86_32))
		all = !user_mode(regs);

	__show_regs(regs, all);

	/*
	 * When in-kernel, we also print out the stack at the time of the fault..
	 */
	if (!user_mode(regs))
		show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
}

Project: linux
File: fault.c

static void dump_pagetable(unsigned long address)
{
	pgd_t *base = __va(read_cr3_pa());
	pgd_t *pgd = base + pgd_index(address);
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	if (bad_address(pgd))
		goto bad;

	pr_info("PGD %lx ", pgd_val(*pgd));

	if (!pgd_present(*pgd))
		goto out;

	p4d = p4d_offset(pgd, address);
	if (bad_address(p4d))
		goto bad;

	pr_cont("P4D %lx ", p4d_val(*p4d));
	if (!p4d_present(*p4d) || p4d_large(*p4d))
		goto out;

	pud = pud_offset(p4d, address);
	if (bad_address(pud))
		goto bad;

	pr_cont("PUD %lx ", pud_val(*pud));
	if (!pud_present(*pud) || pud_large(*pud))
		goto out;

	pmd = pmd_offset(pud, address);
	if (bad_address(pmd))
		goto bad;

	pr_cont("PMD %lx ", pmd_val(*pmd));
	if (!pmd_present(*pmd) || pmd_large(*pmd))
		goto out;

	pte = pte_offset_kernel(pmd, address);
	if (bad_address(pte))
		goto bad;

	pr_cont("PTE %lx", pte_val(*pte));
out:
	pr_cont("\n");
	return;
bad:
	pr_info("BAD\n");
}

Project: linux
File: dumpstack.c

int __die(const char *str, struct pt_regs *regs, long err)
{
	/* Save the regs of the first oops for the executive summary later. */
	if (!die_counter)
		exec_summary_regs = *regs;

	printk(KERN_DEFAULT
	       "%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter,
	       IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT"         : "",
	       IS_ENABLED(CONFIG_SMP)     ? " SMP"             : "",
	       debug_pagealloc_enabled()  ? " DEBUG_PAGEALLOC" : "",
	       IS_ENABLED(CONFIG_KASAN)   ? " KASAN"           : "",
	       IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION) ?
	       (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : "");

	show_regs(regs);
	print_modules();

	if (notify_die(DIE_OOPS, str, regs, err,
			current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
		return 1;

	return 0;
}

Project: linux
File: dumpstack.c

void show_stack_regs(struct pt_regs *regs)
{
	show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
}

Project: linux
File: fault.c

__do_page_fault(struct pt_regs *regs, unsigned long error_code,
		unsigned long address)
{
	struct vm_area_struct *vma;
	struct task_struct *tsk;
	struct mm_struct *mm;
	vm_fault_t fault, major = 0;
	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
	u32 pkey;

	tsk = current;
	mm = tsk->mm;

	prefetchw(&mm->mmap_sem);

	if (unlikely(kmmio_fault(regs, address)))
		return;

	/*
	 * We fault-in kernel-space virtual memory on-demand. The
	 * 'reference' page table is init_mm.pgd.
	 *
	 * NOTE! We MUST NOT take any locks for this case. We may
	 * be in an interrupt or a critical region, and should
	 * only copy the information from the master page table,
	 * nothing more.
	 *
	 * This verifies that the fault happens in kernel space
	 * (error_code & 4) == 0, and that the fault was not a
	 * protection error (error_code & 9) == 0.
	 */
	if (unlikely(fault_in_kernel_space(address))) {
		if (!(error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
			if (vmalloc_fault(address) >= 0)
				return;
		}

		/* Can handle a stale RO->RW TLB: */
		if (spurious_fault(error_code, address))
			return;

		/* kprobes don't want to hook the spurious faults: */
		if (kprobes_fault(regs))
			return;
		/*
		 * Don't take the mm semaphore here. If we fixup a prefetch
		 * fault we could otherwise deadlock:
		 */
		bad_area_nosemaphore(regs, error_code, address, NULL);

		return;
	}

	/* kprobes don't want to hook the spurious faults: */
	if (unlikely(kprobes_fault(regs)))
		return;

	if (unlikely(error_code & X86_PF_RSVD))
		pgtable_bad(regs, error_code, address);

	if (unlikely(smap_violation(error_code, regs))) {
		bad_area_nosemaphore(regs, error_code, address, NULL);
		return;
	}

	/*
	 * 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)) {
		bad_area_nosemaphore(regs, error_code, address, NULL);
		return;
	}

	/*
	 * It's safe to allow irq's after cr2 has been saved and the
	 * vmalloc fault has been handled.
	 *
	 * User-mode registers count as a user access even for any
	 * potential system fault or CPU buglet:
	 */
	if (user_mode(regs)) {
		local_irq_enable();
		error_code |= X86_PF_USER;
		flags |= FAULT_FLAG_USER;
	} else {
		if (regs->flags & X86_EFLAGS_IF)
			local_irq_enable();
	}

	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);

	if (error_code & X86_PF_WRITE)
		flags |= FAULT_FLAG_WRITE;
	if (error_code & X86_PF_INSTR)
		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_sem 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(!down_read_trylock(&mm->mmap_sem))) {
		if (!(error_code & X86_PF_USER) &&
		    !search_exception_tables(regs->ip)) {
			bad_area_nosemaphore(regs, error_code, address, NULL);
			return;
		}
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 = find_vma(mm, address);
	if (unlikely(!vma)) {
		bad_area(regs, error_code, address);
		return;
	}
	if (likely(vma->vm_start <= address))
		goto good_area;
	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
		bad_area(regs, error_code, address);
		return;
	}
	if (error_code & X86_PF_USER) {
		/*
		 * Accessing the stack below %sp is always a bug.
		 * The large cushion allows instructions like enter
		 * and pusha to work. ("enter $65535, $31" pushes
		 * 32 pointers and then decrements %sp by 65535.)
		 */
		if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
			bad_area(regs, error_code, address);
			return;
		}
	}
	if (unlikely(expand_stack(vma, address))) {
		bad_area(regs, error_code, address);
		return;
	}

	/*
	 * Ok, we have a good vm_area for this memory access, so
	 * we can handle it..
	 */
good_area:
	if (unlikely(access_error(error_code, vma))) {
		bad_area_access_error(regs, error_code, address, vma);
		return;
	}

	/*
	 * If for any reason at all we couldn't handle the fault,
	 * make sure we exit gracefully rather than endlessly redo
	 * the fault.  Since we never set FAULT_FLAG_RETRY_NOWAIT, if
	 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
	 *
	 * Note that handle_userfault() may also release and reacquire mmap_sem
	 * (and not return with VM_FAULT_RETRY), when returning to userland to
	 * repeat the page fault later with a VM_FAULT_NOPAGE retval
	 * (potentially after handling any pending signal during the return to
	 * userland). The return to userland is identified whenever
	 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
	 * Thus we have to be careful about not touching vma after handling the
	 * fault, so we read the pkey beforehand.
	 */
	pkey = vma_pkey(vma);
	fault = handle_mm_fault(vma, address, flags);
	major |= fault & VM_FAULT_MAJOR;

	/*
	 * If we need to retry the mmap_sem has already been released,
	 * and if there is a fatal signal pending there is no guarantee
	 * that we made any progress. Handle this case first.
	 */
	if (unlikely(fault & VM_FAULT_RETRY)) {
		/* Retry at most once */
		if (flags & FAULT_FLAG_ALLOW_RETRY) {
			flags &= ~FAULT_FLAG_ALLOW_RETRY;
			flags |= FAULT_FLAG_TRIED;
			if (!fatal_signal_pending(tsk))
				goto retry;
		}

		/* User mode? Just return to handle the fatal exception */
		if (flags & FAULT_FLAG_USER)
			return;

		/* Not returning to user mode? Handle exceptions or die: */
		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
		return;
	}

	up_read(&mm->mmap_sem);
	if (unlikely(fault & VM_FAULT_ERROR)) {
		mm_fault_error(regs, error_code, address, &pkey, fault);
		return;
	}

	/*
	 * Major/minor page fault accounting. If any of the events
	 * returned VM_FAULT_MAJOR, we account it as a major fault.
	 */
	if (major) {
		tsk->maj_flt++;
		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
	} else {
		tsk->min_flt++;
		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
	}

	check_v8086_mode(regs, address, tsk);
}