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Message-ID: <CAKv+Gu_mHpuvC4X_SeY-BLw7AiAnnmTcE0QyPvYiJRtLY4rr_g@mail.gmail.com>
Date: Thu, 8 Jun 2017 10:02:58 +0000
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: Dave Young <dyoung@...hat.com>
Cc: "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Matt Fleming <matt@...eblueprint.co.uk>,
tripleshiftone@...il.com
Subject: Re: [PATCH] x86/efi: fix boot panic because of invalid bgrt image address
On 8 June 2017 at 05:32, Dave Young <dyoung@...hat.com> wrote:
> Maniaxx <tripleshiftone@...il.com> reported kernel boot panic similar to below:
> (emulated the panic with using same invalid phys addr in a uefi vm)
> There are also a bug in bugzilla.kernel.org:
> https://bugzilla.kernel.org/show_bug.cgi?id=195633
>
> This happens after below commit:
> 7b0a911 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.
>
> With original efi bgrt code we initialize bgrt late
> and use ioremap to map the image address. In ioremap code we check the
> address is a valid physical address or not before really map it.
>
> With current new efi bgrt code we moved the initialization to early code
> so we switch to early_memremap which does not check the phys_addr like
> ioremap does. This lead to the early kernel panics.
>
> Fix this by checking the image physical address, if it is not within
> any EFI_BOOT_SERVICES_DATA areas then we just bail out. It is stronger
> then the original ioremap checking, according to spec the BGRT data
> should fall into EFI_BOOT_SERVICES_DATA.
>
Which spec? The UEFI spec does not mention BGRT, and given that it is
an ACPI table, I would expect an ACPI reclaim region to be the most
appropriate. A quick test with QEMU confirms this:
ACPI: BGRT 0x000000013A5E0000 000038 (v01 INTEL EDK2 00000002
01000013)
and
efi: 0x00013a5e0000-0x00013a5effff [ACPI Reclaim Memory| | | |
| | | | |WB| | | ]
So while I agree that we have to fix this, and that checking the BGRT
address against the UEFI memory map is the most appropriate course of
action, requiring a certain region type is probably not what we want.
We have a similar check for ESRT, in efi_mem_desc_lookup(), which
looks a bit dodgy tbh, given that it allows any region type (including
MMIO), as long as it has the EFI_MEMORY_RUNTIME attribute, which is
almost certainly incorrect.
So what I would like to see is a function that can tell you whether a
certain address is covered by a region of a type that is normal
memory, and is occupied, i.e.,
EFI_RESERVED_TYPE
EFI_LOADER_CODE
EFI_LOADER_DATA
EFI_BOOT_SERVICES_CODE
EFI_BOOT_SERVICES_DATA
EFI_RUNTIME_SERVICES_CODE
EFI_RUNTIME_SERVICES_DATA
EFI_ACPI_RECLAIM_MEMORY
EFI_ACPI_MEMORY_NVS
The EFI_MEMORY_RUNTIME attribute is irrelevant: the firmware itself
does not have to read these tables at runtime, so it doesn't matter
whether the O/S maps them on its behalf.
If you could please stick that in drivers/firmware/efi/efi.c, and
rework the patch to use it instead? I will move the ESRT code to it as
well once this is merged.
> [ 0.000000] BUG: unable to handle kernel paging request at ffffffffff280001
> [ 0.000000] IP: efi_bgrt_init+0xfb/0x153
> [ 0.000000] PGD 6e00b067
> [ 0.000000] P4D 6e00b067
> [ 0.000000] PUD 6e00d067
> [ 0.000000] PMD 6e221067
> [ 0.000000] PTE 8a08e01800000163
> [ 0.000000]
> [ 0.000000] Oops: 0009 [#1] SMP
> [ 0.000000] Modules linked in:
> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.12.0-rc4+ #135
> [ 0.000000] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> [ 0.000000] task: ffffffff9840f4c0 task.stack: ffffffff98400000
> [ 0.000000] RIP: 0010:efi_bgrt_init+0xfb/0x153
> [ 0.000000] RSP: 0000:ffffffff98403d50 EFLAGS: 00010082
> [ 0.000000] RAX: ffffffffff280001 RBX: 0000000000000000 RCX: 0000000000000006
> [ 0.000000] RDX: 0a08e01800001000 RSI: 8a08e01800000163 RDI: 000000000000057e
> [ 0.000000] RBP: ffffffff98403d68 R08: 0000000000000041 R09: 0000000000000002
> [ 0.000000] R10: 0000000000000000 R11: ffff8c063cff8fc6 R12: ffffffff981d1fb2
> [ 0.000000] R13: ffffffff986b4fa0 R14: 0000000000000010 R15: 0000000000000000
> [ 0.000000] FS: 0000000000000000(0000) GS:ffffffff984db000(0000) knlGS:0000000000000000
> [ 0.000000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 0.000000] CR2: ffffffffff280001 CR3: 000000006e00a000 CR4: 00000000000406b0
> [ 0.000000] Call Trace:
> [ 0.000000] ? bgrt_init+0xbc/0xbc
> [ 0.000000] acpi_parse_bgrt+0xe/0x12
> [ 0.000000] acpi_table_parse+0x89/0xb8
> [ 0.000000] acpi_boot_init+0x445/0x4e2
> [ 0.000000] ? acpi_parse_x2apic+0x79/0x79
> [ 0.000000] ? dmi_ignore_irq0_timer_override+0x33/0x33
> [ 0.000000] setup_arch+0xb63/0xc82
> [ 0.000000] ? early_idt_handler_array+0x120/0x120
> [ 0.000000] start_kernel+0xb7/0x443
> [ 0.000000] ? early_idt_handler_array+0x120/0x120
> [ 0.000000] x86_64_start_reservations+0x29/0x2b
> [ 0.000000] x86_64_start_kernel+0x154/0x177
> [ 0.000000] secondary_startup_64+0x9f/0x9f
> [ 0.000000] Code: 3f ff eb 6c 48 bf 01 00 00 00 18 e0 08 0a be 06 00 00 00 e8 ef 2b fe ff 48 85 c0 75 0e 48 c7 c7 88 09 22 98 e8 e1 31 3f ff eb 45 <66> 44 8b 20 be 06 00 00 00 48 89 c7 8b 58 02 e8 91 2c fe ff 66
> [ 0.000000] RIP: efi_bgrt_init+0xfb/0x153 RSP: ffffffff98403d50
> [ 0.000000] CR2: ffffffffff280001
> [ 0.000000] ---[ end trace 9843d3b7cbcab26a ]---
> [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task!
> [ 0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task!
>
> Fixes: 7b0a911 efi/x86: Move the EFI BGRT init code to early init code
> Reported-by: Maniaxx <tripleshiftone@...il.com>
> Signed-off-by: Dave Young <dyoung@...hat.com>
> ---
> drivers/firmware/efi/efi-bgrt.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> --- linux.orig/drivers/firmware/efi/efi-bgrt.c
> +++ linux/drivers/firmware/efi/efi-bgrt.c
> @@ -27,6 +27,31 @@ struct bmp_header {
> u32 size;
> } __packed;
>
> +static bool efi_bgrt_addr_valid(u64 addr)
> +{
> + efi_memory_desc_t *md;
> +
> + if (!efi_enabled(EFI_MEMMAP)) {
> + pr_err("EFI_MEMMAP is not enabled.\n");
> + return true;
> + }
> +
> + 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;
> @@ -65,6 +90,10 @@ 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");
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