On 2021/9/16 下午6:02, Peter Zijlstra wrote:
> On Thu, Sep 16, 2021 at 10:03:19AM +0200, Peter Zijlstra wrote:
>
>> Oh, I'm an idiot... yes it tries to read regs the stack, but clearly
>> that won't work for the guard page.
>
> OK, extended it to also cover task and IRQ stacks. get_stack_info()
> doesn't seem to know about SOFTIRQ stacks on 64bit, might have to look
> into that next.
>
> Andy, what's the story with page_fault_oops(), according to the comment
> in exc_double_fault() actual stack overflows will always hit #DF.
Just give this one a test, still not working properly...
[ 51.016033][ C0] traps: PANIC: double fault, error_code: 0x0
[ 51.016047][ C0] double fault: 0000 [#1] SMP PTI
[ 51.016054][ C0] CPU: 0 PID: 761 Comm: a.out Not tainted 5.14.0-next-20210913+ #543
[ 51.016061][ C0] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[ 51.016065][ C0] RIP: 0010:perf_swevent_get_recursion_context+0x0/0x70
[ 51.016079][ C0] Code: 48 03 43 28 48 8b 0c 24 bb 01 00 00 00 4c 29 f0 48 39 c8 48 0f 47 c1 49 89 45 08 e9 48 ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 <55> 53 e8 09 20 f2 ff 48 c7 c2 20 4d 03 00 65 48 03 15 5a 3b d2 7e
[ 51.016086][ C0] RSP: 0018:fffffe000000b000 EFLAGS: 00010046
[ 51.016093][ C0] RAX: 0000000080120008 RBX: fffffe000000b050 RCX: 0000000000000000
[ 51.016097][ C0] RDX: ffff888106c3c300 RSI: ffffffff81269031 RDI: 000000000000001c
[ 51.016102][ C0] RBP: 000000000000001c R08: 0000000000000001 R09: 0000000000000000
[ 51.016106][ C0] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[ 51.016109][ C0] R13: fffffe000000b044 R14: 0000000000000001 R15: 0000000000000001
[ 51.016113][ C0] FS: 00007f0cfd961740(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
[ 51.016120][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 51.016124][ C0] CR2: fffffe000000aff8 CR3: 0000000105ecc001 CR4: 00000000003606f0
[ 51.016129][ C0] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 51.016132][ C0] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 51.016136][ C0] Call Trace:
[ 51.016139][ C0] <TASK>
[ 51.016141][ C0] </TASK>
[ 51.016144][ C0] Modules linked in:
[ 51.042436][ C0] ---[ end trace 5c102ce76b073dcf ]---
[ 51.042440][ C0] RIP: 0010:perf_swevent_get_recursion_context+0x0/0x70
[ 51.042450][ C0] Code: 48 03 43 28 48 8b 0c 24 bb 01 00 00 00 4c 29 f0 48 39 c8 48 0f 47 c1 49 89 45 08 e9 48 ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 <55> 53 e8 09 20 f2 ff 48 c7 c2 20 4d 03 00 65 48 03 15 5a 3b d2 7e
[ 51.042457][ C0] RSP: 0018:fffffe000000b000 EFLAGS: 00010046
[ 51.042462][ C0] RAX: 0000000080120008 RBX: fffffe000000b050 RCX: 0000000000000000
[ 51.042466][ C0] RDX: ffff888106c3c300 RSI: ffffffff81269031 RDI: 000000000000001c
[ 51.042470][ C0] RBP: 000000000000001c R08: 0000000000000001 R09: 0000000000000000
[ 51.042479][ C0] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[ 51.042483][ C0] R13: fffffe000000b044 R14: 0000000000000001 R15: 0000000000000001
[ 51.042487][ C0] FS: 00007f0cfd961740(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
[ 51.042493][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 51.042497][ C0] CR2: fffffe000000aff8 CR3: 0000000105ecc001 CR4: 00000000003606f0
[ 51.042501][ C0] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 51.042505][ C0] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 51.042510][ C0] Kernel panic - not syncing: Fatal exception in interrupt
[ 51.042917][ C0] Kernel Offset: disabled
Regards,
Michael Wang
>
> ---
> diff --git a/arch/x86/include/asm/cpu_entry_area.h b/arch/x86/include/asm/cpu_entry_area.h
> index 3d52b094850a..c4e92462c2b4 100644
> --- a/arch/x86/include/asm/cpu_entry_area.h
> +++ b/arch/x86/include/asm/cpu_entry_area.h
> @@ -61,6 +61,9 @@ enum exception_stack_ordering {
> #define CEA_ESTACK_OFFS(st) \
> offsetof(struct cea_exception_stacks, st## _stack)
>
> +#define CEA_EGUARD_OFFS(st) \
> + offsetof(struct cea_exception_stacks, st## _stack_guard)
> +
> #define CEA_ESTACK_PAGES \
> (sizeof(struct cea_exception_stacks) / PAGE_SIZE)
>
> diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
> index f248eb2ac2d4..8ff346579330 100644
> --- a/arch/x86/include/asm/stacktrace.h
> +++ b/arch/x86/include/asm/stacktrace.h
> @@ -14,13 +14,14 @@
> #include <asm/switch_to.h>
>
> enum stack_type {
> - STACK_TYPE_UNKNOWN,
> + STACK_TYPE_UNKNOWN = 0,
> STACK_TYPE_TASK,
> STACK_TYPE_IRQ,
> STACK_TYPE_SOFTIRQ,
> STACK_TYPE_ENTRY,
> STACK_TYPE_EXCEPTION,
> STACK_TYPE_EXCEPTION_LAST = STACK_TYPE_EXCEPTION + N_EXCEPTION_STACKS-1,
> + STACK_TYPE_GUARD = 0x80,
> };
>
> struct stack_info {
> @@ -31,6 +32,15 @@ struct stack_info {
> bool in_task_stack(unsigned long *stack, struct task_struct *task,
> struct stack_info *info);
>
> +static __always_inline bool in_stack_guard(void *addr, void *begin, void *end)
> +{
> +#ifdef CONFIG_VMAP_STACK
> + if (addr > (begin - PAGE_SIZE))
> + return true;
> +#endif
> + return false;
> +}
> +
> bool in_entry_stack(unsigned long *stack, struct stack_info *info);
>
> int get_stack_info(unsigned long *stack, struct task_struct *task,
> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> index ea4fe192189d..91b406fe2a39 100644
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -32,12 +32,19 @@ static struct pt_regs exec_summary_regs;
> bool noinstr 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)
> + void *begin = task_stack_page(task);
> + void *end = begin + THREAD_SIZE;
> + int type = STACK_TYPE_TASK;
> +
> + if ((void *)stack < begin || (void *)stack >= end) {
> + if (in_stack_guard(stack, begin, end)) {
> + type |= STACK_TYPE_GUARD;
> + goto fill_info;
> + }
> return false;
> + }
>
> +fill_info:
> info->type = STACK_TYPE_TASK;
> info->begin = begin;
> info->end = end;
> @@ -50,14 +57,20 @@ bool noinstr in_task_stack(unsigned long *stack, struct task_struct *task,
> bool noinstr in_entry_stack(unsigned long *stack, struct stack_info *info)
> {
> struct entry_stack *ss = cpu_entry_stack(smp_processor_id());
> -
> + int type = STACK_TYPE_ENTRY;
> void *begin = ss;
> void *end = ss + 1;
>
> - if ((void *)stack < begin || (void *)stack >= end)
> + if ((void *)stack < begin || (void *)stack >= end) {
> + if (in_stack_guard(stack, begin, end)) {
> + type |= STACK_TYPE_GUARD;
> + goto fill_info;
> + }
> return false;
> + }
>
> - info->type = STACK_TYPE_ENTRY;
> +fill_info:
> + info->type = type;
> info->begin = begin;
> info->end = end;
> info->next_sp = NULL;
> diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
> index 5601b95944fa..3634bdf9ab36 100644
> --- a/arch/x86/kernel/dumpstack_64.c
> +++ b/arch/x86/kernel/dumpstack_64.c
> @@ -32,9 +32,15 @@ const char *stack_type_name(enum stack_type type)
> {
> BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
>
> + if (type == STACK_TYPE_TASK)
> + return "TASK";
> +
> if (type == STACK_TYPE_IRQ)
> return "IRQ";
>
> + if (type == STACK_TYPE_SOFTIRQ)
> + return "SOFTIRQ";
> +
> if (type == STACK_TYPE_ENTRY) {
> /*
> * On 64-bit, we have a generic entry stack that we
> @@ -63,6 +69,11 @@ struct estack_pages {
> };
>
> #define EPAGERANGE(st) \
> + [PFN_DOWN(CEA_EGUARD_OFFS(st))] = { \
> + .offs = CEA_EGUARD_OFFS(st), \
> + .size = PAGE_SIZE, \
> + .type = STACK_TYPE_GUARD + \
> + STACK_TYPE_EXCEPTION + ESTACK_ ##st, }, \
> [PFN_DOWN(CEA_ESTACK_OFFS(st)) ... \
> PFN_DOWN(CEA_ESTACK_OFFS(st) + CEA_ESTACK_SIZE(st) - 1)] = { \
> .offs = CEA_ESTACK_OFFS(st), \
> @@ -111,7 +122,7 @@ static __always_inline bool in_exception_stack(unsigned long *stack, struct stac
> k = (stk - begin) >> PAGE_SHIFT;
> /* Lookup the page descriptor */
> ep = &estack_pages[k];
> - /* Guard page? */
> + /* unknown entry */
> if (!ep->size)
> return false;
>
> @@ -122,7 +133,12 @@ static __always_inline bool in_exception_stack(unsigned long *stack, struct stac
> info->type = ep->type;
> info->begin = (unsigned long *)begin;
> info->end = (unsigned long *)end;
> - info->next_sp = (unsigned long *)regs->sp;
> + info->next_sp = NULL;
> +
> + /* Can't read regs from a guard page. */
> + if (!(ep->type & STACK_TYPE_GUARD))
> + info->next_sp = (unsigned long *)regs->sp;
> +
> return true;
> }
>
> @@ -130,6 +146,7 @@ static __always_inline bool in_irq_stack(unsigned long *stack, struct stack_info
> {
> unsigned long *end = (unsigned long *)this_cpu_read(hardirq_stack_ptr);
> unsigned long *begin;
> + int type = STACK_TYPE_IRQ;
>
> /*
> * @end points directly to the top most stack entry to avoid a -8
> @@ -144,19 +161,27 @@ static __always_inline bool in_irq_stack(unsigned long *stack, struct stack_info
> * final operation is 'popq %rsp' which means after that RSP points
> * to the original stack and not to @end.
> */
> - if (stack < begin || stack >= end)
> + if (stack < begin || stack >= end) {
> + if (in_stack_guard(stack, begin, end)) {
> + type |= STACK_TYPE_GUARD;
> + goto fill_info;
> + }
> return false;
> + }
>
> - info->type = STACK_TYPE_IRQ;
> +fill_info:
> + info->type = type;
> info->begin = begin;
> info->end = end;
> + info->next_sp = NULL;
>
> /*
> * The next stack pointer is stored at the top of the irq stack
> * before switching to the irq stack. Actual stack entries are all
> * below that.
> */
> - info->next_sp = (unsigned long *)*(end - 1);
> + if (!(type & STACK_TYPE_GUARD))
> + info->next_sp = (unsigned long *)*(end - 1);
>
> return true;
> }
> @@ -193,6 +218,9 @@ int get_stack_info(unsigned long *stack, struct task_struct *task,
> if (!get_stack_info_noinstr(stack, task, info))
> goto unknown;
>
> + if (info->type & STACK_TYPE_GUARD)
> + goto unknown;
> +
> /*
> * Make sure we don't iterate through any given stack more than once.
> * If it comes up a second time then there's something wrong going on:
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index a58800973aed..80f6d8d735eb 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -353,6 +353,7 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
>
> #ifdef CONFIG_VMAP_STACK
> unsigned long address = read_cr2();
> + struct stack_info info;
> #endif
>
> #ifdef CONFIG_X86_ESPFIX64
> @@ -455,9 +456,11 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
> * stack even if the actual trigger for the double fault was
> * something else.
> */
> - if ((unsigned long)task_stack_page(tsk) - 1 - address < PAGE_SIZE) {
> - handle_stack_overflow("kernel stack overflow (double-fault)",
> - regs, address);
> + if (get_stack_info_noinstr((void *)address, current, &info) &&
> + info.type & STACK_TYPE_GUARD) {
> + const char *name = stack_type_name(info.type & ~STACK_TYPE_GUARD);
> + pr_emerg("BUG: %s stack guard hit at %p (stack is %p..%p)\n",
> + name, (void *)address, info.begin, info.end);
> }
> #endif
>
> @@ -708,7 +711,9 @@ asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *r
> sp = regs->sp;
> stack = (unsigned long *)sp;
>
> - if (!get_stack_info_noinstr(stack, current, &info) || info.type == STACK_TYPE_ENTRY ||
> + if (!get_stack_info_noinstr(stack, current, &info) ||
> + info.type & STACK_TYPE_GUARD ||
> + info.type == STACK_TYPE_ENTRY ||
> info.type >= STACK_TYPE_EXCEPTION_LAST)
> sp = __this_cpu_ist_top_va(VC2);
>
>
