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From: Ingo Molnar <mingo@kernel.org>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: linux-efi@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 17/17] efi/libstub/arm64: handle randomized TEXT_OFFSET
Date: Mon, 14 May 2018 08:47:01 +0200	[thread overview]
Message-ID: <20180514064701.GC16596@gmail.com> (raw)
In-Reply-To: <20180504060003.19618-18-ard.biesheuvel@linaro.org>


* Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> From: Mark Rutland <mark.rutland@arm.com>
> 
> When CONFIG_RANDOMIZE_TEXT_OFFSET is selected, TEXT_OFFSET is an
> arbitrary multiple of PAGE_SIZE in the interval [0, 2MB).
> 
> The EFI stub does not account for the potential misalignment of
> TEXT_OFFSET relative to EFI_KIMG_ALIGN, and produces a randomized
> physical offset which is always a round multiple of EFI_KIMG_ALIGN.
> This may result in statically allocated objects whose alignment exceeds
> PAGE_SIZE to appear misaligned in memory. This has been observed to
> result in spurious stack overflow reports and failure to make use of
> the IRQ stacks, and theoretically could result in a number of other
> issues.
> 
> We can OR in the low bits of TEXT_OFFSET to ensure that we have the
> necessary offset (and hence preserve the misalignment of TEXT_OFFSET
> relative to EFI_KIMG_ALIGN), so let's do that.
> 
> Fixes: 6f26b3671184c36d ("arm64: kaslr: increase randomization granularity")
> Cc: <stable@vger.kernel.org> # v4.7+
> Reported-by: Kim Phillips <kim.phillips@arm.com>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Tested-by: Kim Phillips <kim.phillips@arm.com>
> [ardb: clarify commit log]
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  drivers/firmware/efi/libstub/arm64-stub.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
> index b9bd827caa22..541b82fdc8a2 100644
> --- a/drivers/firmware/efi/libstub/arm64-stub.c
> +++ b/drivers/firmware/efi/libstub/arm64-stub.c
> @@ -97,6 +97,13 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table_arg,
>  		u32 offset = !IS_ENABLED(CONFIG_DEBUG_ALIGN_RODATA) ?
>  			     (phys_seed >> 32) & mask : TEXT_OFFSET;
>  
> +		/*
> +		 * With CONFIG_RANDOMIZE_TEXT_OFFSET, TEXT_OFFSET may not be a
> +		 * multiple of EFI_KIMG_ALIGN, and we must ensure that we apply
> +		 * the offset below EFI_KIMG_ALIGN.
> +		 */

When referring to config variables in comments and changelogs I'd suggest a bit 
more verbosity:

  s/CONFIG_RANDOMIZE_TEXT_OFFSET
   /CONFIG_RANDOMIZE_TEXT_OFFSET=y

... because at first I thought (based on the name) that 
CONFIG_RANDOMIZE_TEXT_OFFSET is an actual integer offset value - while it's a 
bool. The =y makes the bool nature obvious.

( Similarly, when negated the canonical way to refer to it is 
  !CONFIG_RANDOMIZE_TEXT_OFFSET. )

> +		offset |= (TEXT_OFFSET % EFI_KIMG_ALIGN);

The parentheses are not needed here I think.

Thanks,

	Ingo

  reply	other threads:[~2018-05-14  6:47 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-04  5:59 [GIT PULL 00/17] EFI updates for v4.18 Ard Biesheuvel
2018-05-04  5:59 ` [PATCH 01/17] x86/xen/efi: Initialize UEFI secure boot state during dom0 boot Ard Biesheuvel
2018-05-14  7:43   ` [tip:efi/core] " tip-bot for Daniel Kiper
2018-05-04  5:59 ` [PATCH 02/17] efi/cper: Remove the INDENT_SP silliness Ard Biesheuvel
2018-05-14  7:44   ` [tip:efi/core] " tip-bot for Borislav Petkov
2018-05-04  5:59 ` [PATCH 03/17] efi: Fix IA32/X64 Processor Error Record definition Ard Biesheuvel
2018-05-14  7:44   ` [tip:efi/core] " tip-bot for Yazen Ghannam
2018-05-04  5:59 ` [PATCH 04/17] efi: Decode IA32/X64 Processor Error Section Ard Biesheuvel
2018-05-14  7:45   ` [tip:efi/core] " tip-bot for Yazen Ghannam
2018-05-04  5:59 ` [PATCH 05/17] efi: Decode IA32/X64 Processor Error Info Structure Ard Biesheuvel
2018-05-14  7:45   ` [tip:efi/core] " tip-bot for Yazen Ghannam
2018-05-04  5:59 ` [PATCH 06/17] efi: Decode UEFI-defined IA32/X64 Error Structure GUIDs Ard Biesheuvel
2018-05-14  7:46   ` [tip:efi/core] " tip-bot for Yazen Ghannam
2018-05-04  5:59 ` [PATCH 07/17] efi: Decode IA32/X64 Cache, TLB, and Bus Check structures Ard Biesheuvel
2018-05-14  7:46   ` [tip:efi/core] " tip-bot for Yazen Ghannam
2018-05-04  5:59 ` [PATCH 08/17] efi: Decode additional IA32/X64 Bus Check fields Ard Biesheuvel
2018-05-14  7:47   ` [tip:efi/core] " tip-bot for Yazen Ghannam
2018-05-04  5:59 ` [PATCH 09/17] efi: Decode IA32/X64 MS Check structure Ard Biesheuvel
2018-05-14  7:47   ` [tip:efi/core] " tip-bot for Yazen Ghannam
2018-05-04  5:59 ` [PATCH 10/17] efi: Decode IA32/X64 Context Info structure Ard Biesheuvel
2018-05-14  7:48   ` [tip:efi/core] " tip-bot for Yazen Ghannam
2018-05-04  5:59 ` [PATCH 11/17] efi/libstub/tpm: Make function efi_retrieve_tpm2_eventlog_1_2() static Ard Biesheuvel
2018-05-14  7:48   ` [tip:efi/core] " tip-bot for Wei Yongjun
2018-05-04  5:59 ` [PATCH 12/17] efi: fix efi_pci_io_protocol32 prototype for mixed mode Ard Biesheuvel
2018-05-14  6:57   ` Ingo Molnar
2018-05-14  7:02     ` Ard Biesheuvel
2018-05-14  7:42   ` [tip:efi/core] efi: Avoid potential crashes, fix the 'struct efi_pci_io_protocol_32' definition " tip-bot for Ard Biesheuvel
2018-05-04  5:59 ` [PATCH 13/17] efi: align efi_pci_io_protocol typedefs to type naming convention Ard Biesheuvel
2018-05-14  7:49   ` [tip:efi/core] efi: Align " tip-bot for Ard Biesheuvel
2018-05-04  6:00 ` [PATCH 14/17] efi/x86: fold __setup_efi_pci32 and __setup_efi_pci64 into one Ard Biesheuvel
2018-05-14  7:49   ` [tip:efi/core] efi/x86: Fold __setup_efi_pci32() and __setup_efi_pci64() into one function tip-bot for Ard Biesheuvel
2018-05-04  6:00 ` [PATCH 15/17] efi/x86: Ignore unrealistically large option roms Ard Biesheuvel
2018-05-14  6:40   ` Ingo Molnar
2018-05-14  6:43   ` [PATCH] efi/x86: Clean up the eboot code a bit Ingo Molnar
2018-05-14  6:47     ` Ard Biesheuvel
2018-05-14  6:58       ` Ingo Molnar
2018-05-14  6:59         ` Ard Biesheuvel
2018-05-14  7:50   ` [tip:efi/core] efi/x86: Ignore unrealistically large option ROMs tip-bot for Hans de Goede
2018-05-15  9:18     ` Ard Biesheuvel
2018-06-21 15:13       ` Ingo Molnar
2018-05-04  6:00 ` [PATCH 16/17] efi/capsule-loader: Don't output reset log when reset flags are not set Ard Biesheuvel
2018-05-14  7:50   ` [tip:efi/core] " tip-bot for Shunyong Yang
2018-05-04  6:00 ` [PATCH 17/17] efi/libstub/arm64: handle randomized TEXT_OFFSET Ard Biesheuvel
2018-05-14  6:47   ` Ingo Molnar [this message]
2018-05-14  6:48     ` Ard Biesheuvel
2018-05-14  7:00       ` Ingo Molnar
2018-05-14  7:01         ` Ard Biesheuvel

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