forked from Minki/linux
b08418b548
There's some daring kernel code out there which dumps the stack of another task without first making sure the task is inactive. If the task happens to be running while the unwinder is reading the stack, unusual unwinder warnings can result. There's no race-free way for the unwinder to know whether such a warning is legitimate, so just disable unwinder warnings for all non-current tasks. Reviewed-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Dave Jones <dsj@fb.com> Cc: Jann Horn <jannh@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Link: https://lore.kernel.org/r/ec424a2aea1d461eb30cab48a28c6433de2ab784.1587808742.git.jpoimboe@redhat.com
199 lines
4.8 KiB
C
199 lines
4.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
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*/
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#include <linux/sched/debug.h>
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#include <linux/kallsyms.h>
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#include <linux/kprobes.h>
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#include <linux/uaccess.h>
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#include <linux/hardirq.h>
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#include <linux/kdebug.h>
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#include <linux/export.h>
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#include <linux/ptrace.h>
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#include <linux/kexec.h>
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#include <linux/sysfs.h>
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#include <linux/bug.h>
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#include <linux/nmi.h>
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#include <asm/cpu_entry_area.h>
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#include <asm/stacktrace.h>
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static const char * const exception_stack_names[] = {
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[ ESTACK_DF ] = "#DF",
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[ ESTACK_NMI ] = "NMI",
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[ ESTACK_DB2 ] = "#DB2",
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[ ESTACK_DB1 ] = "#DB1",
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[ ESTACK_DB ] = "#DB",
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[ ESTACK_MCE ] = "#MC",
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};
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const char *stack_type_name(enum stack_type type)
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{
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BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
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if (type == STACK_TYPE_IRQ)
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return "IRQ";
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if (type == STACK_TYPE_ENTRY) {
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/*
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* On 64-bit, we have a generic entry stack that we
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* use for all the kernel entry points, including
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* SYSENTER.
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*/
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return "ENTRY_TRAMPOLINE";
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}
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if (type >= STACK_TYPE_EXCEPTION && type <= STACK_TYPE_EXCEPTION_LAST)
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return exception_stack_names[type - STACK_TYPE_EXCEPTION];
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return NULL;
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}
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/**
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* struct estack_pages - Page descriptor for exception stacks
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* @offs: Offset from the start of the exception stack area
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* @size: Size of the exception stack
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* @type: Type to store in the stack_info struct
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*/
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struct estack_pages {
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u32 offs;
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u16 size;
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u16 type;
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};
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#define EPAGERANGE(st) \
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[PFN_DOWN(CEA_ESTACK_OFFS(st)) ... \
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PFN_DOWN(CEA_ESTACK_OFFS(st) + CEA_ESTACK_SIZE(st) - 1)] = { \
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.offs = CEA_ESTACK_OFFS(st), \
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.size = CEA_ESTACK_SIZE(st), \
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.type = STACK_TYPE_EXCEPTION + ESTACK_ ##st, }
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/*
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* Array of exception stack page descriptors. If the stack is larger than
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* PAGE_SIZE, all pages covering a particular stack will have the same
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* info. The guard pages including the not mapped DB2 stack are zeroed
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* out.
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*/
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static const
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struct estack_pages estack_pages[CEA_ESTACK_PAGES] ____cacheline_aligned = {
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EPAGERANGE(DF),
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EPAGERANGE(NMI),
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EPAGERANGE(DB1),
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EPAGERANGE(DB),
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EPAGERANGE(MCE),
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};
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static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
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{
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unsigned long begin, end, stk = (unsigned long)stack;
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const struct estack_pages *ep;
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struct pt_regs *regs;
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unsigned int k;
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BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
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begin = (unsigned long)__this_cpu_read(cea_exception_stacks);
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/*
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* Handle the case where stack trace is collected _before_
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* cea_exception_stacks had been initialized.
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*/
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if (!begin)
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return false;
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end = begin + sizeof(struct cea_exception_stacks);
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/* Bail if @stack is outside the exception stack area. */
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if (stk < begin || stk >= end)
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return false;
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/* Calc page offset from start of exception stacks */
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k = (stk - begin) >> PAGE_SHIFT;
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/* Lookup the page descriptor */
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ep = &estack_pages[k];
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/* Guard page? */
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if (!ep->size)
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return false;
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begin += (unsigned long)ep->offs;
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end = begin + (unsigned long)ep->size;
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regs = (struct pt_regs *)end - 1;
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info->type = ep->type;
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info->begin = (unsigned long *)begin;
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info->end = (unsigned long *)end;
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info->next_sp = (unsigned long *)regs->sp;
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return true;
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}
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static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
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{
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unsigned long *end = (unsigned long *)this_cpu_read(hardirq_stack_ptr);
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unsigned long *begin = end - (IRQ_STACK_SIZE / sizeof(long));
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/*
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* This is a software stack, so 'end' can be a valid stack pointer.
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* It just means the stack is empty.
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*/
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if (stack < begin || stack >= end)
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return false;
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info->type = STACK_TYPE_IRQ;
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info->begin = begin;
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info->end = end;
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/*
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* The next stack pointer is the first thing pushed by the entry code
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* after switching to the irq stack.
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*/
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info->next_sp = (unsigned long *)*(end - 1);
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return true;
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}
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int get_stack_info(unsigned long *stack, struct task_struct *task,
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struct stack_info *info, unsigned long *visit_mask)
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{
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if (!stack)
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goto unknown;
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task = task ? : current;
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if (in_task_stack(stack, task, info))
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goto recursion_check;
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if (task != current)
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goto unknown;
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if (in_exception_stack(stack, info))
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goto recursion_check;
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if (in_irq_stack(stack, info))
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goto recursion_check;
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if (in_entry_stack(stack, info))
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goto recursion_check;
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goto unknown;
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recursion_check:
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/*
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* Make sure we don't iterate through any given stack more than once.
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* If it comes up a second time then there's something wrong going on:
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* just break out and report an unknown stack type.
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*/
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if (visit_mask) {
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if (*visit_mask & (1UL << info->type)) {
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if (task == current)
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printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
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goto unknown;
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}
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*visit_mask |= 1UL << info->type;
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}
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return 0;
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unknown:
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info->type = STACK_TYPE_UNKNOWN;
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return -EINVAL;
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}
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