[PATCH 4.4 07/27] x86/efi-bgrt: Fix kernel panic when mapping BGRT data

Greg Kroah-Hartman
2017-12-04T16:00:33Z

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},