[PATCH] kexec-tools/x86: get_kernel_vaddr_and_size off-by-one fix

[PATCH] kexec-tools/x86: get_kernel_vaddr_and_size off-by-one fix

[Dave Young]

I got below error while tesing kexec -p:
"Can't find kernel text map area from kcore"

The case is the pt_load start addr was same as stext_sym. The checking
code should really be saddr <= stext_sym so that the right pt_load area
includes stext_sym can be matched.

This was not reported by people previously because it will fail over to
use hardcode X86_64__START_KERNEL_map to match the pt_load areas again
in later code and it sometimes succeeds because of kernel address
randomization.

With this change according to my test stext_sym checking can garantee
falling into right pt_load area if we get correct stext_sym.

Signed-off-by: Dave Young <dyoung@redhat.com>
---
 kexec/arch/i386/crashdump-x86.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- kexec-tools.orig/kexec/arch/i386/crashdump-x86.c
+++ kexec-tools/kexec/arch/i386/crashdump-x86.c
@@ -205,7 +205,7 @@ static int get_kernel_vaddr_and_size(str
 			unsigned long long size;
 
 			/* Look for kernel text mapping header. */
-			if (saddr < stext_sym && eaddr > stext_sym) {
+			if (saddr <= stext_sym && eaddr > stext_sym) {
 				saddr = _ALIGN_DOWN(saddr, X86_64_KERN_VADDR_ALIGN);
 				elf_info->kern_vaddr_start = saddr;
 				size = eaddr - saddr;

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Re: [PATCH] kexec-tools/x86: get_kernel_vaddr_and_size off-by-one fix

[Simon Horman]

On Thu, Dec 08, 2016 at 10:52:22AM +0800, Dave Young wrote:
> I got below error while tesing kexec -p:
> "Can't find kernel text map area from kcore"
> 
> The case is the pt_load start addr was same as stext_sym. The checking
> code should really be saddr <= stext_sym so that the right pt_load area
> includes stext_sym can be matched.
> 
> This was not reported by people previously because it will fail over to
> use hardcode X86_64__START_KERNEL_map to match the pt_load areas again
> in later code and it sometimes succeeds because of kernel address
> randomization.
> 
> With this change according to my test stext_sym checking can garantee
> falling into right pt_load area if we get correct stext_sym.
> 
> Signed-off-by: Dave Young <dyoung@redhat.com>

Thanks, applied.

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