Patch "efi: Fix boot panic because of invalid BGRT image address" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

efi: Fix boot panic because of invalid BGRT image address

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
efi-fix-boot-panic-because-of-invalid-bgrt-image-address.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dave Young <[email protected]>
Date: Fri, 9 Jun 2017 08:45:58 +0000
Subject: efi: Fix boot panic because of invalid BGRT image address

From: Dave Young <[email protected]>

commit 792ef14df5c585c19b2831673a077504a09e5203 upstream.

Maniaxx reported a kernel boot crash in the EFI code, which I emulated by using same invalid phys addr in code:

  BUG: unable to handle kernel paging request at ffffffffff280001
  IP: efi_bgrt_init+0xfb/0x153
  ...
  Call Trace:
   ? bgrt_init+0xbc/0xbc
   acpi_parse_bgrt+0xe/0x12
   acpi_table_parse+0x89/0xb8
   acpi_boot_init+0x445/0x4e2
   ? acpi_parse_x2apic+0x79/0x79
   ? dmi_ignore_irq0_timer_override+0x33/0x33
   setup_arch+0xb63/0xc82
   ? early_idt_handler_array+0x120/0x120
   start_kernel+0xb7/0x443
   ? early_idt_handler_array+0x120/0x120
   x86_64_start_reservations+0x29/0x2b
   x86_64_start_kernel+0x154/0x177
   secondary_startup_64+0x9f/0x9f

There is also a similar bug filed in bugzilla.kernel.org:

https://bugzilla.kernel.org/show_bug.cgi?id=195633

The crash is caused by this commit:

7b0a911478c7 efi/x86: Move the EFI BGRT init code to early init code

The root cause is the firmware on those machines provides invalid BGRT image addresses.

In a kernel before above commit BGRT initializes late and uses ioremap() to map the image address. Ioremap validates the address, if it is not a valid physical address ioremap() just fails and returns. However in current kernel EFI BGRT initializes early and uses early_memremap() which does not validate the image address, and kernel panic happens.

According to ACPI spec the BGRT image address should fall into EFI_BOOT_SERVICES_DATA, see the section 5.2.22.4 of below document:

http://www.uefi.org/sites/default/files/resources/ACPI_6_1.pdf

Fix this issue by validating the image address in efi_bgrt_init(). If the image address does not fall into any EFI_BOOT_SERVICES_DATA areas we just bail out with a warning message.

---
 arch/x86/platform/efi/efi-bgrt.c |   26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

@@ -27,6 +27,26 @@ struct bmp_header {
 	u32 size;
 } __packed;
 
+static bool efi_bgrt_addr_valid(u64 addr)
+{
+	efi_memory_desc_t *md;
+
+	for_each_efi_memory_desc(md) {
+		u64 size;
+		u64 end;
+
+		if (md->type != EFI_BOOT_SERVICES_DATA)
+			continue;
+
+		size = md->num_pages << EFI_PAGE_SHIFT;
+		end = md->phys_addr + size;
+		if (addr >= md->phys_addr && addr < end)
+			return true;
+	}
+
+	return false;
+}
+
 void __init efi_bgrt_init(struct acpi_table_header *table)
 {
 	void *image;

@@ -36,7 +56,7 @@ void __init efi_bgrt_init(struct acpi_ta
 	if (acpi_disabled)
 		return;
 
-	if (!efi_enabled(EFI_BOOT))
+	if (!efi_enabled(EFI_MEMMAP))
 		return;
 
 	if (table->length < sizeof(bgrt_tab)) {

@@ -65,6 +85,10 @@ void __init efi_bgrt_init(struct acpi_ta
 		goto out;
 	}
 
+	if (!efi_bgrt_addr_valid(bgrt->image_address)) {
+		pr_notice("Ignoring BGRT: invalid image address\n");
+		goto out;
+	}
 	image = early_memremap(bgrt->image_address, sizeof(bmp_header));
 	if (!image) {
 		pr_notice("Ignoring BGRT: failed to map image header memory\n");

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/efi-fix-boot-panic-because-of-invalid-bgrt-image-address.patch