From 09503379dc99535b1bbfa51aa1aeef340f5d82ec Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Thu, 13 Feb 2014 17:17:54 +0000 Subject: [PATCH] x86/efi: Check status field to validate BGRT header Madper reported seeing the following crash, BUG: unable to handle kernel paging request at ffffffffff340003 IP: [] efi_bgrt_init+0x9d/0x133 Call Trace: [] efi_late_init+0x9/0xb [] start_kernel+0x436/0x450 [] ? repair_env_string+0x5c/0x5c [] ? early_idt_handlers+0x120/0x120 [] x86_64_start_reservations+0x2a/0x2c [] x86_64_start_kernel+0x13e/0x14d This is caused because the layout of the ACPI BGRT header on this system doesn't match the definition from the ACPI spec, and so we get a bogus physical address when dereferencing ->image_address in efi_bgrt_init(). Luckily the status field in the BGRT header clearly marks it as invalid, so we can check that field and skip BGRT initialisation. Reported-by: Madper Xie Suggested-by: Toshi Kani Cc: "Rafael J. Wysocki" Cc: Matthew Garrett Cc: Josh Triplett Signed-off-by: Matt Fleming --- arch/x86/platform/efi/efi-bgrt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/platform/efi/efi-bgrt.c b/arch/x86/platform/efi/efi-bgrt.c index 4df9591eadad..f15103dff4b4 100644 --- a/arch/x86/platform/efi/efi-bgrt.c +++ b/arch/x86/platform/efi/efi-bgrt.c @@ -42,7 +42,7 @@ void __init efi_bgrt_init(void) if (bgrt_tab->header.length < sizeof(*bgrt_tab)) return; - if (bgrt_tab->version != 1) + if (bgrt_tab->version != 1 || bgrt_tab->status != 1) return; if (bgrt_tab->image_type != 0 || !bgrt_tab->image_address) return;