x86/dumpstack: Fix interrupt and exception stack boundary checks

On x86_64, the double fault exception stack is located immediately after
the interrupt stack in memory.  This causes confusion in the unwinder
when it tries to unwind through an empty interrupt stack, where the
stack pointer points to the address bordering the two stacks.  The
unwinder incorrectly thinks it's running on the double fault stack.

Fix this kind of stack border confusion by never considering the
beginning address of an exception or interrupt stack to be part of the
stack.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Fixes: 5fe599e02e41 ("x86/dumpstack: Add support for unwinding empty IRQ stacks")
Link: http://lkml.kernel.org/r/bcc142160a5104de5c354c21c394c93a0173943f.1499786555.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index e5f0b40e66d238b931d14d78ea579abd195a3350..4f04814749037e403f063a33a3249896a4c97f55 100644 (file)
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -37,7 +37,7 @@ static bool in_hardirq_stack(unsigned long *stack, struct stack_info *info)
         * This is a software stack, so 'end' can be a valid stack pointer.
         * It just means the stack is empty.
         */
-       if (stack < begin || stack > end)
+       if (stack <= begin || stack > end)
                return false;
 
        info->type      = STACK_TYPE_IRQ;
@@ -62,7 +62,7 @@ static bool in_softirq_stack(unsigned long *stack, struct stack_info *info)
         * This is a software stack, so 'end' can be a valid stack pointer.
         * It just means the stack is empty.
         */
-       if (stack < begin || stack > end)
+       if (stack <= begin || stack > end)
                return false;
 
        info->type      = STACK_TYPE_SOFTIRQ;

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 3e1471d5748723069d70577fd9061a1cb26770ba..225af4184f06bf4d343eb1eb43ded549299fc031 100644 (file)
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -55,7 +55,7 @@ static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
                begin = end - (exception_stack_sizes[k] / sizeof(long));
                regs  = (struct pt_regs *)end - 1;
 
-               if (stack < begin || stack >= end)
+               if (stack <= begin || stack >= end)
                        continue;
 
                info->type      = STACK_TYPE_EXCEPTION + k;
@@ -78,7 +78,7 @@ static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
         * This is a software stack, so 'end' can be a valid stack pointer.
         * It just means the stack is empty.
         */
-       if (stack < begin || stack > end)
+       if (stack <= begin || stack > end)
                return false;
 
        info->type      = STACK_TYPE_IRQ;