[PATCH] nvme/lightnvm: Prevent small buffer overflow in nvme_nvm_identify

[Matias Bjørling]

On 02/24/2017 04:43 PM, Keith Busch wrote:
> +Matias
>
> On Thu, Feb 23, 2017 at 06:48:47PM -0700, Scott Bauer wrote:
>> There are two closely named structs in lightnvm:
>> struct nvme_nvm_addr_format and
>> struct nvme_addr_format.
>>
>> The first struct has 4 reserved bytes at the end, the second does not.
>> (gdb) p sizeof(struct nvme_nvm_addr_format)
>> $1 = 16
>> (gdb) p sizeof(struct nvm_addr_format)
>> $2 = 12
>
> We need Matias to resolve what the size of these structs are supposed
> to be. There is a compile time assert:
>
> 	sizeof(struct nvme_nvm_addr_format) == 128
>
> that should clearly fail, but the compiler removes _nvme_nvm_check_size
> since it's not called from anywhere. lightnvm has a couple badly assumed
> struct sizes, but I don't know if the struct is incorrectly defined or
> if the assert is wrong.

Hi Scott,

You're right. I thought that was fixed a while ago.

The sizes are correct for both nvme_nvm_addr_format (the internal nvme 
structure that is described from the device), and the nvm_addr_format 
that is the host representation.

Luckily the memory is later overwritten by the group setup, and does not 
write into memory outside of lightnvm.

I'll post a patch that fixes up the asserts and pick up your patch for 4.12.

Thanks,
Matias

>
>> In the nvme_nvm_identify function we memcpy from the larger struct to the
>> smaller struct. We incorrectly pass the length of the larger struct
>> and overflow by 4 bytes, lets not do that.
>>
>> Signed-off-by: Scott Bauer <scott.bauer at intel.com>
>> ---
>>  drivers/nvme/host/lightnvm.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
>> index 21cac85..fd98954 100644
>> --- a/drivers/nvme/host/lightnvm.c
>> +++ b/drivers/nvme/host/lightnvm.c
>> @@ -324,7 +324,7 @@ static int nvme_nvm_identity(struct nvm_dev *nvmdev, struct nvm_id *nvm_id)
>>  	nvm_id->cap = le32_to_cpu(nvme_nvm_id->cap);
>>  	nvm_id->dom = le32_to_cpu(nvme_nvm_id->dom);
>>  	memcpy(&nvm_id->ppaf, &nvme_nvm_id->ppaf,
>> -					sizeof(struct nvme_nvm_addr_format));
>> +					sizeof(struct nvm_addr_format));