The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the EFI binary does not rely on pages that are both executable and writable.
The flag is used by some distro versions of GRUB to decide if the EFI binary may be executed.
As the Linux kernel neither has RWX sections nor needs RWX pages for relocation we should set the flag.
Cc: Ard Biesheuvel ardb@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com --- arch/riscv/kernel/efi-header.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi-header.S index 515b2dfbca75..c5f17c2710b5 100644 --- a/arch/riscv/kernel/efi-header.S +++ b/arch/riscv/kernel/efi-header.S @@ -64,7 +64,7 @@ extra_header_fields: .long efi_header_end - _start // SizeOfHeaders .long 0 // CheckSum .short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem - .short 0 // DllCharacteristics + .short IMAGE_DLL_CHARACTERISTICS_NX_COMPAT // DllCharacteristics .quad 0 // SizeOfStackReserve .quad 0 // SizeOfStackCommit .quad 0 // SizeOfHeapReserve
Heinrich Schuchardt wrote:
The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the EFI binary does not rely on pages that are both executable and writable.
The flag is used by some distro versions of GRUB to decide if the EFI binary may be executed.
As the Linux kernel neither has RWX sections nor needs RWX pages for relocation we should set the flag.
Cc: Ard Biesheuvel ardb@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com
Makes sense to me. This was applied a year ago on arm64:
3c66bb1918c2 ("arm64: efi: Set NX compat flag in PE/COFF header")
..and before that on x86
24b72bb12e84 ("efi: x86: Set the NX-compatibility flag in the PE header")
Reviewed-by: Emil Renner Berthing emil.renner.berthing@canonical.com
arch/riscv/kernel/efi-header.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi-header.S index 515b2dfbca75..c5f17c2710b5 100644 --- a/arch/riscv/kernel/efi-header.S +++ b/arch/riscv/kernel/efi-header.S @@ -64,7 +64,7 @@ extra_header_fields: .long efi_header_end - _start // SizeOfHeaders .long 0 // CheckSum .short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem
- .short 0 // DllCharacteristics
- .short IMAGE_DLL_CHARACTERISTICS_NX_COMPAT // DllCharacteristics .quad 0 // SizeOfStackReserve .quad 0 // SizeOfStackCommit .quad 0 // SizeOfHeapReserve
-- 2.45.2
linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
Hi Heinrich,
On 29/09/2024 16:02, Heinrich Schuchardt wrote:
The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the EFI binary does not rely on pages that are both executable and writable.
The flag is used by some distro versions of GRUB to decide if the EFI binary may be executed.
As the Linux kernel neither has RWX sections nor needs RWX pages for relocation we should set the flag.
Cc: Ard Biesheuvel ardb@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com
arch/riscv/kernel/efi-header.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi-header.S index 515b2dfbca75..c5f17c2710b5 100644 --- a/arch/riscv/kernel/efi-header.S +++ b/arch/riscv/kernel/efi-header.S @@ -64,7 +64,7 @@ extra_header_fields: .long efi_header_end - _start // SizeOfHeaders .long 0 // CheckSum .short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem
- .short 0 // DllCharacteristics
- .short IMAGE_DLL_CHARACTERISTICS_NX_COMPAT // DllCharacteristics .quad 0 // SizeOfStackReserve .quad 0 // SizeOfStackCommit .quad 0 // SizeOfHeapReserve
I don't understand if this fixes something or not: what could go wrong if we don't do this?
Thanks,
Alex
On 01.10.24 15:51, Alexandre Ghiti wrote:
Hi Heinrich,
On 29/09/2024 16:02, Heinrich Schuchardt wrote:
The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the EFI binary does not rely on pages that are both executable and writable.
The flag is used by some distro versions of GRUB to decide if the EFI binary may be executed.
As the Linux kernel neither has RWX sections nor needs RWX pages for relocation we should set the flag.
Cc: Ard Biesheuvel ardb@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com
arch/riscv/kernel/efi-header.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi- header.S index 515b2dfbca75..c5f17c2710b5 100644 --- a/arch/riscv/kernel/efi-header.S +++ b/arch/riscv/kernel/efi-header.S @@ -64,7 +64,7 @@ extra_header_fields: .long efi_header_end - _start // SizeOfHeaders .long 0 // CheckSum .short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem - .short 0 // DllCharacteristics + .short IMAGE_DLL_CHARACTERISTICS_NX_COMPAT // DllCharacteristics .quad 0 // SizeOfStackReserve .quad 0 // SizeOfStackCommit .quad 0 // SizeOfHeapReserve
I don't understand if this fixes something or not: what could go wrong if we don't do this?
Thanks,
Alex
Hello Alexandre,
https://learn.microsoft.com/en-us/windows-hardware/drivers/bringup/uefi-ca-m... describes Microsoft's effort to improve security by avoiding memory pages that are both executable and writable.
IMAGE_DLL_CHARACTERISTICS_NX_COMPAT is an assertion by the EFI binary that it does not use RWX pages. It may use the EFI_MEMORY_ATTRIBUTE_PROTOCOL to set whether a page is writable or executable (but not both).
When using secure boot, compliant firmware will not allow loading a binary if the flag is not set.
Best regards
Heinrich
Hi Heinrich,
On 01/10/2024 17:24, Heinrich Schuchardt wrote:
On 01.10.24 15:51, Alexandre Ghiti wrote:
Hi Heinrich,
On 29/09/2024 16:02, Heinrich Schuchardt wrote:
The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the EFI binary does not rely on pages that are both executable and writable.
The flag is used by some distro versions of GRUB to decide if the EFI binary may be executed.
As the Linux kernel neither has RWX sections nor needs RWX pages for relocation we should set the flag.
Cc: Ard Biesheuvel ardb@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com
arch/riscv/kernel/efi-header.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi- header.S index 515b2dfbca75..c5f17c2710b5 100644 --- a/arch/riscv/kernel/efi-header.S +++ b/arch/riscv/kernel/efi-header.S @@ -64,7 +64,7 @@ extra_header_fields: .long efi_header_end - _start // SizeOfHeaders .long 0 // CheckSum .short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem - .short 0 // DllCharacteristics + .short IMAGE_DLL_CHARACTERISTICS_NX_COMPAT // DllCharacteristics .quad 0 // SizeOfStackReserve .quad 0 // SizeOfStackCommit .quad 0 // SizeOfHeapReserve
I don't understand if this fixes something or not: what could go wrong if we don't do this?
Thanks,
Alex
Hello Alexandre,
https://learn.microsoft.com/en-us/windows-hardware/drivers/bringup/uefi-ca-m...
describes Microsoft's effort to improve security by avoiding memory pages that are both executable and writable.
IMAGE_DLL_CHARACTERISTICS_NX_COMPAT is an assertion by the EFI binary that it does not use RWX pages. It may use the EFI_MEMORY_ATTRIBUTE_PROTOCOL to set whether a page is writable or executable (but not both).
When using secure boot, compliant firmware will not allow loading a binary if the flag is not set.
Great, so that's a necessary fix, it will get merged in the next rc or so:
Fixes: cb7d2dd5612a ("RISC-V: Add PE/COFF header for EFI stub")
Thanks,
Alex
Best regards
Heinrich
linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
On 09.10.24 09:34, Alexandre Ghiti wrote:
Hi Heinrich,
On 01/10/2024 17:24, Heinrich Schuchardt wrote:
On 01.10.24 15:51, Alexandre Ghiti wrote:
Hi Heinrich,
On 29/09/2024 16:02, Heinrich Schuchardt wrote:
The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the EFI binary does not rely on pages that are both executable and writable.
The flag is used by some distro versions of GRUB to decide if the EFI binary may be executed.
As the Linux kernel neither has RWX sections nor needs RWX pages for relocation we should set the flag.
Cc: Ard Biesheuvel ardb@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com
arch/riscv/kernel/efi-header.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi- header.S index 515b2dfbca75..c5f17c2710b5 100644 --- a/arch/riscv/kernel/efi-header.S +++ b/arch/riscv/kernel/efi-header.S @@ -64,7 +64,7 @@ extra_header_fields: .long efi_header_end - _start // SizeOfHeaders .long 0 // CheckSum .short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem - .short 0 // DllCharacteristics + .short IMAGE_DLL_CHARACTERISTICS_NX_COMPAT // DllCharacteristics .quad 0 // SizeOfStackReserve .quad 0 // SizeOfStackCommit .quad 0 // SizeOfHeapReserve
I don't understand if this fixes something or not: what could go wrong if we don't do this?
Thanks,
Alex
Hello Alexandre,
https://learn.microsoft.com/en-us/windows-hardware/drivers/bringup/ uefi-ca-memory-mitigation-requirements describes Microsoft's effort to improve security by avoiding memory pages that are both executable and writable.
IMAGE_DLL_CHARACTERISTICS_NX_COMPAT is an assertion by the EFI binary that it does not use RWX pages. It may use the EFI_MEMORY_ATTRIBUTE_PROTOCOL to set whether a page is writable or executable (but not both).
When using secure boot, compliant firmware will not allow loading a binary if the flag is not set.
Great, so that's a necessary fix, it will get merged in the next rc or so:
Fixes: cb7d2dd5612a ("RISC-V: Add PE/COFF header for EFI stub")
Thanks for reviewing.
At the time of commit cb7d2dd5612a (2020-10-02) the requirement did not exist. I guess a Fixes: tag is not applicable under these circumstances.
Best regards
Heinrich
On 09/10/2024 09:47, Heinrich Schuchardt wrote:
On 09.10.24 09:34, Alexandre Ghiti wrote:
Hi Heinrich,
On 01/10/2024 17:24, Heinrich Schuchardt wrote:
On 01.10.24 15:51, Alexandre Ghiti wrote:
Hi Heinrich,
On 29/09/2024 16:02, Heinrich Schuchardt wrote:
The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the EFI binary does not rely on pages that are both executable and writable.
The flag is used by some distro versions of GRUB to decide if the EFI binary may be executed.
As the Linux kernel neither has RWX sections nor needs RWX pages for relocation we should set the flag.
Cc: Ard Biesheuvel ardb@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Heinrich Schuchardt
heinrich.schuchardt@canonical.com
arch/riscv/kernel/efi-header.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi- header.S index 515b2dfbca75..c5f17c2710b5 100644 --- a/arch/riscv/kernel/efi-header.S +++ b/arch/riscv/kernel/efi-header.S @@ -64,7 +64,7 @@ extra_header_fields: .long efi_header_end - _start // SizeOfHeaders .long 0 // CheckSum .short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem - .short 0 // DllCharacteristics + .short IMAGE_DLL_CHARACTERISTICS_NX_COMPAT // DllCharacteristics .quad 0 // SizeOfStackReserve .quad 0 // SizeOfStackCommit .quad 0 // SizeOfHeapReserve
I don't understand if this fixes something or not: what could go wrong if we don't do this?
Thanks,
Alex
Hello Alexandre,
https://learn.microsoft.com/en-us/windows-hardware/drivers/bringup/ uefi-ca-memory-mitigation-requirements describes Microsoft's effort to improve security by avoiding memory pages that are both executable and writable.
IMAGE_DLL_CHARACTERISTICS_NX_COMPAT is an assertion by the EFI binary that it does not use RWX pages. It may use the EFI_MEMORY_ATTRIBUTE_PROTOCOL to set whether a page is writable or executable (but not both).
When using secure boot, compliant firmware will not allow loading a binary if the flag is not set.
Great, so that's a necessary fix, it will get merged in the next rc or so:
Fixes: cb7d2dd5612a ("RISC-V: Add PE/COFF header for EFI stub")
Thanks for reviewing.
At the time of commit cb7d2dd5612a (2020-10-02) the requirement did not exist. I guess a Fixes: tag is not applicable under these circumstances.
Hmm ok, indeed that would be weird since it is not the culprit, I'll remove it and it will simply fail to apply for kernels before this commit, no big deal I guess.
Thanks again Heinrich!
Alex
Best regards
Heinrich
On Sun, 29 Sept 2024 at 16:02, Heinrich Schuchardt heinrich.schuchardt@canonical.com wrote:
The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the EFI binary does not rely on pages that are both executable and writable.
The flag is used by some distro versions of GRUB to decide if the EFI binary may be executed.
As the Linux kernel neither has RWX sections nor needs RWX pages for relocation we should set the flag.
Cc: Ard Biesheuvel ardb@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com
Acked-by: Ard Biesheuvel ardb@kernel.org
arch/riscv/kernel/efi-header.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi-header.S index 515b2dfbca75..c5f17c2710b5 100644 --- a/arch/riscv/kernel/efi-header.S +++ b/arch/riscv/kernel/efi-header.S @@ -64,7 +64,7 @@ extra_header_fields: .long efi_header_end - _start // SizeOfHeaders .long 0 // CheckSum .short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem
.short 0 // DllCharacteristics
.short IMAGE_DLL_CHARACTERISTICS_NX_COMPAT // DllCharacteristics .quad 0 // SizeOfStackReserve .quad 0 // SizeOfStackCommit .quad 0 // SizeOfHeapReserve-- 2.45.2
Hello:
This patch was applied to riscv/linux.git (fixes) by Palmer Dabbelt palmer@rivosinc.com:
On Sun, 29 Sep 2024 16:02:33 +0200 you wrote:
The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the EFI binary does not rely on pages that are both executable and writable.
The flag is used by some distro versions of GRUB to decide if the EFI binary may be executed.
[...]
Here is the summary with links: - [1/1] riscv: efi: Set NX compat flag in PE/COFF header https://git.kernel.org/riscv/c/22a159b2d2a1
You are awesome, thank you!
linux-stable-mirror@lists.linaro.org
-
Alexandre Ghiti -
Ard Biesheuvel -
Emil Renner Berthing -
Heinrich Schuchardt -
patchwork-bot+linux-riscv＠kernel.org