[PATCH stable 5.4] arm64: mm: account for hotplug memory when randomizing the linear region
From: Ard Biesheuvel ardb@kernel.org
commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream
As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical memory inside the linear region is chosen early at boot, it is based on the memblock description of memory, which does not cover hotplug memory. The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
So let's limit this randomization of the linear region to ensure that this can no longer happen, by using the CPU's addressable PA range instead. As it is guaranteed that no hotpluggable memory will appear that falls outside of that range, we can safely put this PA range sized window anywhere in the linear region.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Will Deacon will@kernel.org Cc: Steven Price steven.price@arm.com Cc: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com --- arch/arm64/mm/init.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index cbcac03c0e0d..a6034645d6f7 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -392,15 +392,18 @@ void __init arm64_memblock_init(void)
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { extern u16 memstart_offset_seed; - u64 range = linear_region_size - - (memblock_end_of_DRAM() - memblock_start_of_DRAM()); + u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1); + int parange = cpuid_feature_extract_unsigned_field( + mmfr0, ID_AA64MMFR0_PARANGE_SHIFT); + s64 range = linear_region_size - + BIT(id_aa64mmfr0_parange_to_phys_shift(parange));
/* * If the size of the linear region exceeds, by a sufficient - * margin, the size of the region that the available physical - * memory spans, randomize the linear region as well. + * margin, the size of the region that the physical memory can + * span, randomize the linear region as well. */ - if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) { + if (memstart_offset_seed > 0 && range >= (s64)ARM64_MEMSTART_ALIGN) { range /= ARM64_MEMSTART_ALIGN; memstart_addr -= ARM64_MEMSTART_ALIGN * ((range * memstart_offset_seed) >> 16);
From: Ard Biesheuvel ardb@kernel.org
commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream
As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical memory inside the linear region is chosen early at boot, it is based on the memblock description of memory, which does not cover hotplug memory. The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
So let's limit this randomization of the linear region to ensure that this can no longer happen, by using the CPU's addressable PA range instead. As it is guaranteed that no hotpluggable memory will appear that falls outside of that range, we can safely put this PA range sized window anywhere in the linear region.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Will Deacon will@kernel.org Cc: Steven Price steven.price@arm.com Cc: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com --- arch/arm64/mm/init.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 80cc79760e8e..09c219aa9d78 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -401,15 +401,18 @@ void __init arm64_memblock_init(void)
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { extern u16 memstart_offset_seed; - u64 range = linear_region_size - - (memblock_end_of_DRAM() - memblock_start_of_DRAM()); + u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1); + int parange = cpuid_feature_extract_unsigned_field( + mmfr0, ID_AA64MMFR0_PARANGE_SHIFT); + s64 range = linear_region_size - + BIT(id_aa64mmfr0_parange_to_phys_shift(parange));
/* * If the size of the linear region exceeds, by a sufficient - * margin, the size of the region that the available physical - * memory spans, randomize the linear region as well. + * margin, the size of the region that the physical memory can + * span, randomize the linear region as well. */ - if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) { + if (memstart_offset_seed > 0 && range >= (s64)ARM64_MEMSTART_ALIGN) { range /= ARM64_MEMSTART_ALIGN; memstart_addr -= ARM64_MEMSTART_ALIGN * ((range * memstart_offset_seed) >> 16);
On 1/9/25 08:54, Florian Fainelli wrote:
From: Ard Biesheuvel ardb@kernel.org
commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream
As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical memory inside the linear region is chosen early at boot, it is based on the memblock description of memory, which does not cover hotplug memory. The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
So let's limit this randomization of the linear region to ensure that this can no longer happen, by using the CPU's addressable PA range instead. As it is guaranteed that no hotpluggable memory will appear that falls outside of that range, we can safely put this PA range sized window anywhere in the linear region.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Will Deacon will@kernel.org Cc: Steven Price steven.price@arm.com Cc: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com
Forgot to update the patch subject, but this one is for 5.10.
On Thu, Jan 09, 2025 at 09:01:13AM -0800, Florian Fainelli wrote:
On 1/9/25 08:54, Florian Fainelli wrote:
From: Ard Biesheuvel ardb@kernel.org
commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream
As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical memory inside the linear region is chosen early at boot, it is based on the memblock description of memory, which does not cover hotplug memory. The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
So let's limit this randomization of the linear region to ensure that this can no longer happen, by using the CPU's addressable PA range instead. As it is guaranteed that no hotpluggable memory will appear that falls outside of that range, we can safely put this PA range sized window anywhere in the linear region.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Will Deacon will@kernel.org Cc: Steven Price steven.price@arm.com Cc: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com
Forgot to update the patch subject, but this one is for 5.10.
You also forgot to tell us _why_ this is needed :(
thanks,
greg k-h
On 1/12/2025 3:54 AM, Greg KH wrote:
On Thu, Jan 09, 2025 at 09:01:13AM -0800, Florian Fainelli wrote:
On 1/9/25 08:54, Florian Fainelli wrote:
From: Ard Biesheuvel ardb@kernel.org
commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream
As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical memory inside the linear region is chosen early at boot, it is based on the memblock description of memory, which does not cover hotplug memory. The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
So let's limit this randomization of the linear region to ensure that this can no longer happen, by using the CPU's addressable PA range instead. As it is guaranteed that no hotpluggable memory will appear that falls outside of that range, we can safely put this PA range sized window anywhere in the linear region.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Will Deacon will@kernel.org Cc: Steven Price steven.price@arm.com Cc: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com
Forgot to update the patch subject, but this one is for 5.10.
You also forgot to tell us _why_ this is needed :(
This is explained in the second part of the first paragraph:
The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
We use both memory hotplug and KASLR on our systems and that's how we eventually found out about the bug.
On Mon, Jan 13, 2025 at 07:44:50AM -0800, Florian Fainelli wrote:
On 1/12/2025 3:54 AM, Greg KH wrote:
On Thu, Jan 09, 2025 at 09:01:13AM -0800, Florian Fainelli wrote:
On 1/9/25 08:54, Florian Fainelli wrote:
From: Ard Biesheuvel ardb@kernel.org
commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream
As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical memory inside the linear region is chosen early at boot, it is based on the memblock description of memory, which does not cover hotplug memory. The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
So let's limit this randomization of the linear region to ensure that this can no longer happen, by using the CPU's addressable PA range instead. As it is guaranteed that no hotpluggable memory will appear that falls outside of that range, we can safely put this PA range sized window anywhere in the linear region.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Will Deacon will@kernel.org Cc: Steven Price steven.price@arm.com Cc: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com
Forgot to update the patch subject, but this one is for 5.10.
You also forgot to tell us _why_ this is needed :(
This is explained in the second part of the first paragraph:
The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
We use both memory hotplug and KASLR on our systems and that's how we eventually found out about the bug.
And you still have 5.10.y ARM64 systems that need this? Why not move to a newer kernel version already?
Anyway, I need an ack from the ARM64 maintainers that this is ok to apply here before I can take it.
thanks,
greg k-h
On 1/20/2025 5:59 AM, Greg KH wrote:
On Mon, Jan 13, 2025 at 07:44:50AM -0800, Florian Fainelli wrote:
On 1/12/2025 3:54 AM, Greg KH wrote:
On Thu, Jan 09, 2025 at 09:01:13AM -0800, Florian Fainelli wrote:
On 1/9/25 08:54, Florian Fainelli wrote:
From: Ard Biesheuvel ardb@kernel.org
commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream
As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical memory inside the linear region is chosen early at boot, it is based on the memblock description of memory, which does not cover hotplug memory. The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
So let's limit this randomization of the linear region to ensure that this can no longer happen, by using the CPU's addressable PA range instead. As it is guaranteed that no hotpluggable memory will appear that falls outside of that range, we can safely put this PA range sized window anywhere in the linear region.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Will Deacon will@kernel.org Cc: Steven Price steven.price@arm.com Cc: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com
Forgot to update the patch subject, but this one is for 5.10.
You also forgot to tell us _why_ this is needed :(
This is explained in the second part of the first paragraph:
The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
We use both memory hotplug and KASLR on our systems and that's how we eventually found out about the bug.
And you still have 5.10.y ARM64 systems that need this? Why not move to a newer kernel version already?
We still have ARM64 systems running 5.4 that need this, and the same bug applies to 5.10 that we used to support but dropped in favor of 5.15/6.1. Those are the kernel versions used by Android, and Android TV in particular, so it's kind of the way it goes for us.
Anyway, I need an ack from the ARM64 maintainers that this is ok to apply here before I can take it.
Just out of curiosity, the change is pretty innocuous and simple to review, why the extra scrutiny needed here?
[ Sasha's backport helper bot ]
Hi,
The upstream commit SHA1 provided is correct: 97d6786e0669daa5c2f2d07a057f574e849dfd3e
WARNING: Author mismatch between patch and upstream commit: Backport author: Florian Fainelliflorian.fainelli@broadcom.com Commit author: Ard Biesheuvelardb@kernel.org
Status in newer kernel trees: 6.12.y | Present (exact SHA1)
Note: The patch differs from the upstream commit: --- Failed to apply patch cleanly, falling back to interdiff... ---
Results of testing on various branches:
| Branch | Patch Apply | Build Test | |---------------------------|-------------|------------| | stable/linux-6.12.y | Failed | N/A | | stable/linux-6.6.y | Failed | N/A | | stable/linux-6.1.y | Failed | N/A | | stable/linux-5.15.y | Failed | N/A | | stable/linux-5.10.y | Success | Success | | stable/linux-5.4.y | Success | Success |
[ Sasha's backport helper bot ]
Hi,
The upstream commit SHA1 provided is correct: 97d6786e0669daa5c2f2d07a057f574e849dfd3e
WARNING: Author mismatch between patch and upstream commit: Backport author: Florian Fainelliflorian.fainelli@broadcom.com Commit author: Ard Biesheuvelardb@kernel.org
Status in newer kernel trees: 6.12.y | Present (exact SHA1) 6.6.y | Present (exact SHA1) 6.1.y | Present (exact SHA1) 5.15.y | Present (exact SHA1) 5.10.y | Not found 5.4.y | Not found
Note: The patch differs from the upstream commit: --- 1: 97d6786e0669 ! 1: fa6d576248a0 arm64: mm: account for hotplug memory when randomizing the linear region @@ Metadata ## Commit message ## arm64: mm: account for hotplug memory when randomizing the linear region
+ commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream + As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical @@ Commit message Cc: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com + Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com
## arch/arm64/mm/init.c ## @@ arch/arm64/mm/init.c: void __init arm64_memblock_init(void) ---
Results of testing on various branches:
| Branch | Patch Apply | Build Test | |---------------------------|-------------|------------| | stable/linux-5.4.y | Success | Success |
On Thu, Jan 09, 2025 at 08:54:16AM -0800, Florian Fainelli wrote:
From: Ard Biesheuvel ardb@kernel.org
commit 97d6786e0669daa5c2f2d07a057f574e849dfd3e upstream
As a hardening measure, we currently randomize the placement of physical memory inside the linear region when KASLR is in effect. Since the random offset at which to place the available physical memory inside the linear region is chosen early at boot, it is based on the memblock description of memory, which does not cover hotplug memory. The consequence of this is that the randomization offset may be chosen such that any hotplugged memory located above memblock_end_of_DRAM() that appears later is pushed off the end of the linear region, where it cannot be accessed.
So let's limit this randomization of the linear region to ensure that this can no longer happen, by using the CPU's addressable PA range instead. As it is guaranteed that no hotpluggable memory will appear that falls outside of that range, we can safely put this PA range sized window anywhere in the linear region.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Will Deacon will@kernel.org Cc: Steven Price steven.price@arm.com Cc: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20201014081857.3288-1-ardb@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com
arch/arm64/mm/init.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index cbcac03c0e0d..a6034645d6f7 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -392,15 +392,18 @@ void __init arm64_memblock_init(void) if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { extern u16 memstart_offset_seed;
u64 range = linear_region_size -(memblock_end_of_DRAM() - memblock_start_of_DRAM());
u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1);int parange = cpuid_feature_extract_unsigned_field(mmfr0, ID_AA64MMFR0_PARANGE_SHIFT);s64 range = linear_region_size -BIT(id_aa64mmfr0_parange_to_phys_shift(parange));/* * If the size of the linear region exceeds, by a sufficient
* margin, the size of the region that the available physical* memory spans, randomize the linear region as well.
* margin, the size of the region that the physical memory can* span, randomize the linear region as well.
if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
if (memstart_offset_seed > 0 && range >= (s64)ARM64_MEMSTART_ALIGN) { range /= ARM64_MEMSTART_ALIGN; memstart_addr -= ARM64_MEMSTART_ALIGN * ((range * memstart_offset_seed) >> 16);-- 2.43.0
You are not providing any information as to WHY this is needed in stable kernels at all. It just looks like an unsolicted backport with no changes from upstream, yet no hint as to any bug it fixes.
And you all really have hotpluggable memory on systems that are running th is old kernel? Why are they not using newer kernels if they need this? Surely lots of other bugs they need are resolved there, right?
thanks,
greg k-h
linux-stable-mirror@lists.linaro.org
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Florian Fainelli -
Greg KH -
Sasha Levin