x86: check mptable physptr with max_low_pfn on 32bit

Impact: fix early crash on LinuxBIOS systems

Kevin O'Connor reported that Coreboot aka LinuxBIOS tries to put
mptable somewhere very high, well above max_low_pfn (below which
BIOSes generally put the mptable), causing a panic.

The BIOS will probably be changed to be compatible with older
Linus versions, but nevertheless the MP-spec does not forbid
an MP-table in arbitrary system RAM, so make sure it all
works even if the table is in an unexpected place.

Check physptr with max_low_pfn * PAGE_SIZE.

Reported-by: Kevin O'Connor <kevin@koconnor.net>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Stefan Reinauer <stepan@coresystems.de>
Cc: coreboot@coreboot.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 12 insertions, 3 deletions

diff --git a/arch/x86/kernel/mpparse.c b/arch/x86/kernel/mpparse.c
index 7f4d2586972e..37cb1bda1baf 100644
--- a/arch/x86/kernel/mpparse.c
+++ b/arch/x86/kernel/mpparse.c
@@ -710,13 +710,22 @@ static int __init smp_scan_config(unsigned long base, unsigned long length,
                                  * of physical memory; so that simply reserving
                                  * PAGE_SIZE from mpf->physptr yields BUG()
                                  * in reserve_bootmem.
+                                 * also need to make sure physptr is below than
+                                 * max_low_pfn
+                                 * we don't need reserve the area above max_low_pfn
                                  */
                                 unsigned long end = max_low_pfn * PAGE_SIZE;
-                                if (mpf->physptr + size > end)
-                                        size = end - mpf->physptr;
-#endif
+
+                                if (mpf->physptr < end) {
+                                        if (mpf->physptr + size > end)
+                                                size = end - mpf->physptr;
+                                        reserve_bootmem_generic(mpf->physptr, size,
+                                                        BOOTMEM_DEFAULT);
+                                }
+#else
                                 reserve_bootmem_generic(mpf->physptr, size,
                                                 BOOTMEM_DEFAULT);
+#endif
                         }
 
                         return 1;