x86/setup/crash: Check memblock_reserve() retval

memblock_reserve() can fail but the crashkernel reservation code
doesn't check that and this can lead the user into believing
that the crashkernel region was actually reserved. Make sure we
check that return value and we exit early with a failure message
in the error case.
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Young <dyoung@redhat.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Salter <msalter@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: WANG Chao <chaowang@redhat.com>
Cc: jerry_hoemann@hp.com
Link: http://lkml.kernel.org/r/1445246268-26285-7-git-send-email-bp@alien8.deSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/setup.c

@@ -531,7 +531,11 @@ static int __init reserve_crashkernel_low(void)
 		return -ENOMEM;
 	}
 
-	memblock_reserve(low_base, low_size);
+	ret = memblock_reserve(low_base, low_size);
+	if (ret) {
+		pr_err("%s: Error reserving crashkernel low memblock.\n", __func__);
+		return ret;
+	}
 
 	pr_info("Reserving %ldMB of low memory at %ldMB for crashkernel (System low RAM: %ldMB)\n",
 		(unsigned long)(low_size >> 20),
@@ -589,7 +593,11 @@ static void __init reserve_crashkernel(void)
 			return;
 		}
 	}
-	memblock_reserve(crash_base, crash_size);
+	ret = memblock_reserve(crash_base, crash_size);
+	if (ret) {
+		pr_err("%s: Error reserving crashkernel memblock.\n", __func__);
+		return;
+	}
 
 	if (crash_base >= (1ULL << 32) && reserve_crashkernel_low()) {
 		memblock_free(crash_base, crash_size);