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

x86/efi-bgrt: Fix kernel panic when mapping BGRT data

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-efi-bgrt-fix-kernel-panic-when-mapping-bgrt-data.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 50a0cb565246f20d59cdb161778531e4b19d35ac Mon Sep 17 00:00:00 2001

From: Sai Praneeth sai.praneeth.prakhya@intel.com Date: Wed, 9 Dec 2015 15:41:08 -0800 Subject: x86/efi-bgrt: Fix kernel panic when mapping BGRT data

From: Sai Praneeth sai.praneeth.prakhya@intel.com

commit 50a0cb565246f20d59cdb161778531e4b19d35ac upstream.

Starting with this commit 35eb8b81edd4 ("x86/efi: Build our own page table structures") efi regions have a separate page directory called "efi_pgd". In order to access any efi region we have to first shift %cr3 to this page table. In the bgrt code we are trying to copy bgrt_header and image, but these regions fall under "EFI_BOOT_SERVICES_DATA" and to access these regions we have to shift %cr3 to efi_pgd and not doing so will cause page fault as shown below.

[ 0.251599] Last level dTLB entries: 4KB 64, 2MB 0, 4MB 0, 1GB 4 [ 0.259126] Freeing SMP alternatives memory: 32K (ffffffff8230e000 - ffffffff82316000) [ 0.271803] BUG: unable to handle kernel paging request at fffffffefce35002 [ 0.279740] IP: [<ffffffff821bca49>] efi_bgrt_init+0x144/0x1fd [ 0.286383] PGD 300f067 PUD 0 [ 0.289879] Oops: 0000 [#1] SMP [ 0.293566] Modules linked in: [ 0.297039] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.0-rc1-eywa-eywa-built-in-47041+ #2 [ 0.306619] Hardware name: Intel Corporation Skylake Client platform/Skylake Y LPDDR3 RVP3, BIOS SKLSE2R1.R00.B104.B01.1511110114 11/11/2015 [ 0.320925] task: ffffffff820134c0 ti: ffffffff82000000 task.ti: ffffffff82000000 [ 0.329420] RIP: 0010:[<ffffffff821bca49>] [<ffffffff821bca49>] efi_bgrt_init+0x144/0x1fd [ 0.338821] RSP: 0000:ffffffff82003f18 EFLAGS: 00010246 [ 0.344852] RAX: fffffffefce35000 RBX: fffffffefce35000 RCX: fffffffefce2b000 [ 0.352952] RDX: 000000008a82b000 RSI: ffffffff8235bb80 RDI: 000000008a835000 [ 0.361050] RBP: ffffffff82003f30 R08: 000000008a865000 R09: ffffffffff202850 [ 0.369149] R10: ffffffff811ad62f R11: 0000000000000000 R12: 0000000000000000 [ 0.377248] R13: ffff88016dbaea40 R14: ffffffff822622c0 R15: ffffffff82003fb0 [ 0.385348] FS: 0000000000000000(0000) GS:ffff88016d800000(0000) knlGS:0000000000000000 [ 0.394533] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 0.401054] CR2: fffffffefce35002 CR3: 000000000300c000 CR4: 00000000003406f0 [ 0.409153] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 0.417252] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 0.425350] Stack: [ 0.427638] ffffffffffffffff ffffffff82256900 ffff88016dbaea40 ffffffff82003f40 [ 0.436086] ffffffff821bbce0 ffffffff82003f88 ffffffff8219c0c2 0000000000000000 [ 0.444533] ffffffff8219ba4a ffffffff822622c0 0000000000083000 00000000ffffffff [ 0.452978] Call Trace: [ 0.455763] [<ffffffff821bbce0>] efi_late_init+0x9/0xb [ 0.461697] [<ffffffff8219c0c2>] start_kernel+0x463/0x47f [ 0.467928] [<ffffffff8219ba4a>] ? set_init_arg+0x55/0x55 [ 0.474159] [<ffffffff8219b120>] ? early_idt_handler_array+0x120/0x120 [ 0.481669] [<ffffffff8219b5ee>] x86_64_start_reservations+0x2a/0x2c [ 0.488982] [<ffffffff8219b72d>] x86_64_start_kernel+0x13d/0x14c [ 0.495897] Code: 00 41 b4 01 48 8b 78 28 e8 09 36 01 00 48 85 c0 48 89 c3 75 13 48 c7 c7 f8 ac d3 81 31 c0 e8 d7 3b fb fe e9 b5 00 00 00 45 84 e4 <44> 8b 6b 02 74 0d be 06 00 00 00 48 89 df e8 ae 34 0$ [ 0.518151] RIP [<ffffffff821bca49>] efi_bgrt_init+0x144/0x1fd [ 0.524888] RSP <ffffffff82003f18> [ 0.528851] CR2: fffffffefce35002 [ 0.532615] ---[ end trace 7b06521e6ebf2aea ]--- [ 0.537852] Kernel panic - not syncing: Attempted to kill the idle task!

As said above one way to fix this bug is to shift %cr3 to efi_pgd but we are not doing that way because it leaks inner details of how we switch to EFI page tables into a new call site and it also adds duplicate code. Instead, we remove the call to efi_lookup_mapped_addr() and always perform early_mem*() instead of early_io*() because we want to remap RAM regions and not I/O regions. We also delete efi_lookup_mapped_addr() because we are no longer using it.

Signed-off-by: Sai Praneeth Prakhya sai.praneeth.prakhya@intel.com Reported-by: Wendy Wang wendy.wang@intel.com Cc: Borislav Petkov bp@suse.de Cc: Josh Triplett josh@joshtriplett.org Cc: Ricardo Neri ricardo.neri@intel.com Cc: Ravi Shankar ravi.v.shankar@intel.com Signed-off-by: Matt Fleming matt@codeblueprint.co.uk Cc: "Ghannam, Yazen" Yazen.Ghannam@amd.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/platform/efi/efi-bgrt.c | 39 ++++++++++++++------------------------- drivers/firmware/efi/efi.c | 32 -------------------------------- 2 files changed, 14 insertions(+), 57 deletions(-)

--- a/arch/x86/platform/efi/efi-bgrt.c +++ b/arch/x86/platform/efi/efi-bgrt.c @@ -28,8 +28,7 @@ struct bmp_header { void __init efi_bgrt_init(void) { acpi_status status; - void __iomem *image; - bool ioremapped = false; + void *image; struct bmp_header bmp_header;

if (acpi_disabled) @@ -70,20 +69,14 @@ void __init efi_bgrt_init(void) return; }

- image = efi_lookup_mapped_addr(bgrt_tab->image_address); + image = early_memremap(bgrt_tab->image_address, sizeof(bmp_header)); if (!image) { - image = early_ioremap(bgrt_tab->image_address, - sizeof(bmp_header)); - ioremapped = true; - if (!image) { - pr_err("Ignoring BGRT: failed to map image header memory\n"); - return; - } + pr_err("Ignoring BGRT: failed to map image header memory\n"); + return; }

- memcpy_fromio(&bmp_header, image, sizeof(bmp_header)); - if (ioremapped) - early_iounmap(image, sizeof(bmp_header)); + memcpy(&bmp_header, image, sizeof(bmp_header)); + early_memunmap(image, sizeof(bmp_header)); bgrt_image_size = bmp_header.size;

bgrt_image = kmalloc(bgrt_image_size, GFP_KERNEL | __GFP_NOWARN); @@ -93,18 +86,14 @@ void __init efi_bgrt_init(void) return; }

- if (ioremapped) { - image = early_ioremap(bgrt_tab->image_address, - bmp_header.size); - if (!image) { - pr_err("Ignoring BGRT: failed to map image memory\n"); - kfree(bgrt_image); - bgrt_image = NULL; - return; - } + image = early_memremap(bgrt_tab->image_address, bmp_header.size); + if (!image) { + pr_err("Ignoring BGRT: failed to map image memory\n"); + kfree(bgrt_image); + bgrt_image = NULL; + return; }

- memcpy_fromio(bgrt_image, image, bgrt_image_size); - if (ioremapped) - early_iounmap(image, bmp_header.size); + memcpy(bgrt_image, image, bgrt_image_size); + early_memunmap(image, bmp_header.size); } --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -325,38 +325,6 @@ u64 __init efi_mem_desc_end(efi_memory_d return end; }

-/* - * We can't ioremap data in EFI boot services RAM, because we've already mapped - * it as RAM. So, look it up in the existing EFI memory map instead. Only - * callable after efi_enter_virtual_mode and before efi_free_boot_services. - */ -void __iomem *efi_lookup_mapped_addr(u64 phys_addr) -{ - struct efi_memory_map *map; - void *p; - map = efi.memmap; - if (!map) - return NULL; - if (WARN_ON(!map->map)) - return NULL; - for (p = map->map; p < map->map_end; p += map->desc_size) { - efi_memory_desc_t *md = p; - u64 size = md->num_pages << EFI_PAGE_SHIFT; - u64 end = md->phys_addr + size; - if (!(md->attribute & EFI_MEMORY_RUNTIME) && - md->type != EFI_BOOT_SERVICES_CODE && - md->type != EFI_BOOT_SERVICES_DATA) - continue; - if (!md->virt_addr) - continue; - if (phys_addr >= md->phys_addr && phys_addr < end) { - phys_addr += md->virt_addr - md->phys_addr; - return (__force void __iomem *)(unsigned long)phys_addr; - } - } - return NULL; -} - static __initdata efi_config_table_type_t common_tables[] = { {ACPI_20_TABLE_GUID, "ACPI 2.0", &efi.acpi20}, {ACPI_TABLE_GUID, "ACPI", &efi.acpi},

Patches currently in stable-queue which might be from sai.praneeth.prakhya@intel.com are

queue-4.4/x86-mm-pat-ensure-cpa-pfn-only-contains-page-frame-numbers.patch queue-4.4/x86-efi-hoist-page-table-switching-code-into-efi_call_virt.patch queue-4.4/x86-efi-build-our-own-page-table-structures.patch queue-4.4/x86-efi-bgrt-replace-early_memremap-with-memremap.patch queue-4.4/x86-efi-bgrt-fix-kernel-panic-when-mapping-bgrt-data.patch