x86/mm/64: Improve stack overflow warnings

[ Upstream commit 44b979fa302cab91bdd2cc982823e5c13202cd4e ]

Current code has an explicit check for hitting the task stack guard;
but overflowing any of the other stacks will get you a non-descript
general #DF warning.

Improve matters by using get_stack_info_noinstr() to detetrmine if and
which stack guard page got hit, enabling a better stack warning.

In specific, Michael Wang reported what turned out to be an NMI
exception stack overflow, which is now clearly reported as such:

  [] BUG: NMI stack guard page was hit at 0000000085fd977b (stack is 000000003a55b09e..00000000d8cce1a5)

Reported-by: Michael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Wang <yun.wang@linux.alibaba.com>
Link: https://lkml.kernel.org/r/YUTE/NuqnaWbST8n@hirez.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/x86/include/asm/irq_stack.h b/arch/x86/include/asm/irq_stack.h
index 562854c..8d55bd1 100644 (file)
--- a/arch/x86/include/asm/irq_stack.h
+++ b/arch/x86/include/asm/irq_stack.h
@@ -77,11 +77,11 @@
  *     Function calls can clobber anything except the callee-saved
  *     registers. Tell the compiler.
  */
-#define call_on_irqstack(func, asm_call, argconstr...)                 \
+#define call_on_stack(stack, func, asm_call, argconstr...)             \
 {                                                                      \
        register void *tos asm("r11");                                  \
                                                                        \
-       tos = ((void *)__this_cpu_read(hardirq_stack_ptr));             \
+       tos = ((void *)(stack));                                        \
                                                                        \
        asm_inline volatile(                                            \
        "movq   %%rsp, (%[tos])                         \n"             \
@@ -98,6 +98,25 @@
        );                                                              \
 }
 
+#define ASM_CALL_ARG0                                                  \
+       "call %P[__func]                                \n"
+
+#define ASM_CALL_ARG1                                                  \
+       "movq   %[arg1], %%rdi                          \n"             \
+       ASM_CALL_ARG0
+
+#define ASM_CALL_ARG2                                                  \
+       "movq   %[arg2], %%rsi                          \n"             \
+       ASM_CALL_ARG1
+
+#define ASM_CALL_ARG3                                                  \
+       "movq   %[arg3], %%rdx                          \n"             \
+       ASM_CALL_ARG2
+
+#define call_on_irqstack(func, asm_call, argconstr...)                 \
+       call_on_stack(__this_cpu_read(hardirq_stack_ptr),               \
+                     func, asm_call, argconstr)
+
 /* Macros to assert type correctness for run_*_on_irqstack macros */
 #define assert_function_type(func, proto)                              \
        static_assert(__builtin_types_compatible_p(typeof(&func), proto))
@@ -147,8 +166,7 @@
  */
 #define ASM_CALL_SYSVEC                                                        \
        "call irq_enter_rcu                             \n"             \
-       "movq   %[arg1], %%rdi                          \n"             \
-       "call %P[__func]                                \n"             \
+       ASM_CALL_ARG1                                                   \
        "call irq_exit_rcu                              \n"
 
 #define SYSVEC_CONSTRAINTS     , [arg1] "r" (regs)
@@ -168,12 +186,10 @@
  */
 #define ASM_CALL_IRQ                                                   \
        "call irq_enter_rcu                             \n"             \
-       "movq   %[arg1], %%rdi                          \n"             \
-       "movl   %[arg2], %%esi                          \n"             \
-       "call %P[__func]                                \n"             \
+       ASM_CALL_ARG2                                                   \
        "call irq_exit_rcu                              \n"
 
-#define IRQ_CONSTRAINTS        , [arg1] "r" (regs), [arg2] "r" (vector)
+#define IRQ_CONSTRAINTS        , [arg1] "r" (regs), [arg2] "r" ((unsigned long)vector)
 
 #define run_irq_on_irqstack_cond(func, regs, vector)                   \
 {                                                                      \
@@ -185,9 +201,6 @@
                              IRQ_CONSTRAINTS, regs, vector);           \
 }
 
-#define ASM_CALL_SOFTIRQ                                               \
-       "call %P[__func]                                \n"
-
 /*
  * Macro to invoke __do_softirq on the irq stack. This is only called from
  * task context when bottom halves are about to be reenabled and soft
@@ -197,7 +210,7 @@
 #define do_softirq_own_stack()                                         \
 {                                                                      \
        __this_cpu_write(hardirq_stack_inuse, true);                    \
-       call_on_irqstack(__do_softirq, ASM_CALL_SOFTIRQ);               \
+       call_on_irqstack(__do_softirq, ASM_CALL_ARG0);                  \
        __this_cpu_write(hardirq_stack_inuse, false);                   \
 }
 

diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index f248eb2..3881b53 100644 (file)
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -38,6 +38,16 @@ int get_stack_info(unsigned long *stack, struct task_struct *task,
 bool get_stack_info_noinstr(unsigned long *stack, struct task_struct *task,
                            struct stack_info *info);
 
+static __always_inline
+bool get_stack_guard_info(unsigned long *stack, struct stack_info *info)
+{
+       /* make sure it's not in the stack proper */
+       if (get_stack_info_noinstr(stack, current, info))
+               return false;
+       /* but if it is in the page below it, we hit a guard */
+       return get_stack_info_noinstr((void *)stack + PAGE_SIZE, current, info);
+}
+
 const char *stack_type_name(enum stack_type type);
 
 static inline bool on_stack(struct stack_info *info, void *addr, size_t len)

diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 7f72000..6221be7 100644 (file)
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -40,9 +40,9 @@ void math_emulate(struct math_emu_info *);
 bool fault_in_kernel_space(unsigned long address);
 
 #ifdef CONFIG_VMAP_STACK
-void __noreturn handle_stack_overflow(const char *message,
-                                     struct pt_regs *regs,
-                                     unsigned long fault_address);
+void __noreturn handle_stack_overflow(struct pt_regs *regs,
+                                     unsigned long fault_address,
+                                     struct stack_info *info);
 #endif
 
 #endif /* _ASM_X86_TRAPS_H */

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 5601b95..6c5defd 100644 (file)
--- 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

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index f3f3034..cc6de3a 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -313,17 +313,19 @@ out:
 }
 
 #ifdef CONFIG_VMAP_STACK
-__visible void __noreturn handle_stack_overflow(const char *message,
-                                               struct pt_regs *regs,
-                                               unsigned long fault_address)
+__visible void __noreturn handle_stack_overflow(struct pt_regs *regs,
+                                               unsigned long fault_address,
+                                               struct stack_info *info)
 {
-       printk(KERN_EMERG "BUG: stack guard page was hit at %p (stack is %p..%p)\n",
-                (void *)fault_address, current->stack,
-                (char *)current->stack + THREAD_SIZE - 1);
-       die(message, regs, 0);
+       const char *name = stack_type_name(info->type);
+
+       printk(KERN_EMERG "BUG: %s stack guard page was hit at %p (stack is %p..%p)\n",
+              name, (void *)fault_address, info->begin, info->end);
+
+       die("stack guard page", regs, 0);
 
        /* Be absolutely certain we don't return. */
-       panic("%s", message);
+       panic("%s stack guard hit", name);
 }
 #endif
 
@@ -353,6 +355,7 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
 
 #ifdef CONFIG_VMAP_STACK
        unsigned long address = read_cr2();
+       struct stack_info info;
 #endif
 
 #ifdef CONFIG_X86_ESPFIX64
@@ -455,10 +458,8 @@ 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_guard_info((void *)address, &info))
+               handle_stack_overflow(regs, address, &info);
 #endif
 
        pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 84a2c8c..4bfed53 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -32,6 +32,7 @@
 #include <asm/pgtable_areas.h>         /* VMALLOC_START, ...           */
 #include <asm/kvm_para.h>              /* kvm_handle_async_pf          */
 #include <asm/vdso.h>                  /* fixup_vdso_exception()       */
+#include <asm/irq_stack.h>
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -631,6 +632,9 @@ static noinline void
 page_fault_oops(struct pt_regs *regs, unsigned long error_code,
                unsigned long address)
 {
+#ifdef CONFIG_VMAP_STACK
+       struct stack_info info;
+#endif
        unsigned long flags;
        int sig;
 
@@ -649,9 +653,7 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
         * that we're in vmalloc space to avoid this.
         */
        if (is_vmalloc_addr((void *)address) &&
-           (((unsigned long)current->stack - 1 - address < PAGE_SIZE) ||
-            address - ((unsigned long)current->stack + THREAD_SIZE) < PAGE_SIZE)) {
-               unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
+           get_stack_guard_info((void *)address, &info)) {
                /*
                 * We're likely to be running with very little stack space
                 * left.  It's plausible that we'd hit this condition but
@@ -662,13 +664,11 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_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));
+               call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*),
+                             handle_stack_overflow,
+                             ASM_CALL_ARG3,
+                             , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
+
                unreachable();
        }
 #endif