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From: Ard Biesheuvel <ard.biesheuvel@arm.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>,
	linux-arm-kernel@lists.infradead.org
Cc: mark.rutland@arm.com, marc.zyngier@arm.com,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Nadav Amit <namit@vmware.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	James Morse <james.morse@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>
Subject: Re: [PATCH 1/4] arm64: module: create module allocations without exec permissions
Date: Tue, 28 May 2019 08:24:50 +0200	[thread overview]
Message-ID: <f67efae5-1565-5459-2877-31bdd1a40c0f@arm.com> (raw)
In-Reply-To: <d82eb4fe-8113-3f8e-f465-26679ebae2df@arm.com>

On 5/28/19 7:35 AM, Anshuman Khandual wrote:
> 
> 
> On 05/23/2019 03:52 PM, Ard Biesheuvel wrote:
>> Now that the core code manages the executable permissions of code
>> regions of modules explicitly, it is no longer necessary to create
> 
> I guess the permission transition for various module sections happen
> through module_enable_[ro|nx]() after allocating via module_alloc().
> 

Indeed.

>> the module vmalloc regions with RWX permissions, and we can create
>> them with RW- permissions instead, which is preferred from a
>> security perspective.
> 
> Makes sense. Will this be followed in all architectures now ?
> 

I am not sure if every architecture implements module_enable_[ro|nx](), 
but if they do, they should probably apply this change as well.

>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
>> ---
>>   arch/arm64/kernel/module.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
>> index 2e4e3915b4d0..88f0ed31d9aa 100644
>> --- a/arch/arm64/kernel/module.c
>> +++ b/arch/arm64/kernel/module.c
>> @@ -41,7 +41,7 @@ void *module_alloc(unsigned long size)
>>   
>>   	p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
>>   				module_alloc_base + MODULES_VSIZE,
>> -				gfp_mask, PAGE_KERNEL_EXEC, 0,
>> +				gfp_mask, PAGE_KERNEL, 0,
>>   				NUMA_NO_NODE, __builtin_return_address(0));
>>   
>>   	if (!p && IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
>> @@ -57,7 +57,7 @@ void *module_alloc(unsigned long size)
>>   		 */
>>   		p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
>>   				module_alloc_base + SZ_4G, GFP_KERNEL,
>> -				PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
>> +				PAGE_KERNEL, 0, NUMA_NO_NODE,
>>   				__builtin_return_address(0));
>>   
>>   	if (p && (kasan_module_alloc(p, size) < 0)) {
>>
> 
> Which just makes sure that PTE_PXN never gets dropped while creating
> these mappings.
> 

Not sure what you mean. Is there a question here?



  reply	other threads:[~2019-05-28  6:25 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-23 10:22 [PATCH 0/4] arm64: wire up VM_FLUSH_RESET_PERMS Ard Biesheuvel
2019-05-23 10:22 ` [PATCH 1/4] arm64: module: create module allocations without exec permissions Ard Biesheuvel
2019-05-28  5:35   ` Anshuman Khandual
2019-05-28  6:24     ` Ard Biesheuvel [this message]
2019-05-23 10:22 ` [PATCH 2/4] arm64/mm: wire up CONFIG_ARCH_HAS_SET_DIRECT_MAP Ard Biesheuvel
2019-05-28  8:10   ` Anshuman Khandual
2019-05-28  8:20     ` Ard Biesheuvel
2019-05-28  8:41       ` Anshuman Khandual
2019-05-28  8:58         ` Ard Biesheuvel
2019-05-23 10:22 ` [PATCH 3/4] arm64/kprobes: set VM_FLUSH_RESET_PERMS on kprobe instruction pages Ard Biesheuvel
2019-05-28  8:20   ` Anshuman Khandual
2019-05-28  8:23     ` Ard Biesheuvel
2019-05-23 10:22 ` [PATCH 4/4] arm64: bpf: do not allocate executable memory Ard Biesheuvel
2019-05-28 10:04 ` [PATCH 0/4] arm64: wire up VM_FLUSH_RESET_PERMS Will Deacon
2019-05-28 10:29   ` Ard Biesheuvel
2019-06-24 11:16   ` Will Deacon
2019-06-24 11:22     ` Ard Biesheuvel
2019-06-24 14:29       ` Ard Biesheuvel
2019-06-24 17:14         ` Catalin Marinas
2019-06-24 17:15           ` Ard Biesheuvel

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