Subject: Re: [PATCH v2] crypto: vmx - Fix sleep-in-atomic bugs

From: Paulo Flabiano Smorigo <[email-masked]>
Date: Thu, 23 Aug 2018 17:34:27 -0300

On 2018-08-22 21:04, Marcelo Henrique Cerri wrote:
> That looks good to me. Maybe Paulo can help testing it.
> 
> --
> Regards,
> Marcelo
> 
> On Wed, Aug 22, 2018 at 08:26:31AM +0200, Ondrej Mosnacek wrote:
>> This patch fixes sleep-in-atomic bugs in AES-CBC and AES-XTS VMX
>> implementations. The problem is that the blkcipher_* functions should
>> not be called in atomic context.
>> 
>> The bugs can be reproduced via the AF_ALG interface by trying to
>> encrypt/decrypt sufficiently large buffers (at least 64 KiB) using the
>> VMX implementations of 'cbc(aes)' or 'xts(aes)'. Such operations then
>> trigger BUG in crypto_yield():
>> 
>> [  891.863680] BUG: sleeping function called from invalid context at 
>> include/crypto/algapi.h:424
>> [  891.864622] in_atomic(): 1, irqs_disabled(): 0, pid: 12347, name: 
>> kcapi-enc
>> [  891.864739] 1 lock held by kcapi-enc/12347:
>> [  891.864811]  #0: 00000000f5d42c46 (sk_lock-AF_ALG){+.+.}, at: 
>> skcipher_recvmsg+0x50/0x530
>> [  891.865076] CPU: 5 PID: 12347 Comm: kcapi-enc Not tainted 
>> 4.19.0-0.rc0.git3.1.fc30.ppc64le #1
>> [  891.865251] Call Trace:
>> [  891.865340] [c0000003387578c0] [c000000000d67ea4] 
>> dump_stack+0xe8/0x164 (unreliable)
>> [  891.865511] [c000000338757910] [c000000000172a58] 
>> ___might_sleep+0x2f8/0x310
>> [  891.865679] [c000000338757990] [c0000000006bff74] 
>> blkcipher_walk_done+0x374/0x4a0
>> [  891.865825] [c0000003387579e0] [d000000007e73e70] 
>> p8_aes_cbc_encrypt+0x1c8/0x260 [vmx_crypto]
>> [  891.865993] [c000000338757ad0] [c0000000006c0ee0] 
>> skcipher_encrypt_blkcipher+0x60/0x80
>> [  891.866128] [c000000338757b10] [c0000000006ec504] 
>> skcipher_recvmsg+0x424/0x530
>> [  891.866283] [c000000338757bd0] [c000000000b00654] 
>> sock_recvmsg+0x74/0xa0
>> [  891.866403] [c000000338757c10] [c000000000b00f64] 
>> ___sys_recvmsg+0xf4/0x2f0
>> [  891.866515] [c000000338757d90] [c000000000b02bb8] 
>> __sys_recvmsg+0x68/0xe0
>> [  891.866631] [c000000338757e30] [c00000000000bbe4] 
>> system_call+0x5c/0x70
>> 
>> Fixes: 8c755ace357c ("crypto: vmx - Adding CBC routines for VMX 
>> module")
>> Fixes: c07f5d3da643 ("crypto: vmx - Adding support for XTS")
>> Cc: [email-masked]
>> Signed-off-by: Ondrej Mosnacek <[email-masked]>
>> ---
>> Still untested, please test and review if possible.
>> 
>> Changes in v2:
>> - fix leaving preemtption, etc. disabled when leaving the function
>>   (I switched to the more obvious and less efficient variant for the
>>   sake of clarity.)
>> 
>>  drivers/crypto/vmx/aes_cbc.c | 30 ++++++++++++++----------------
>>  drivers/crypto/vmx/aes_xts.c | 21 ++++++++++++++-------
>>  2 files changed, 28 insertions(+), 23 deletions(-)
>> 
>> diff --git a/drivers/crypto/vmx/aes_cbc.c 
>> b/drivers/crypto/vmx/aes_cbc.c
>> index 5285ece4f33a..b71895871be3 100644
>> --- a/drivers/crypto/vmx/aes_cbc.c
>> +++ b/drivers/crypto/vmx/aes_cbc.c
>> @@ -107,24 +107,23 @@ static int p8_aes_cbc_encrypt(struct 
>> blkcipher_desc *desc,
>>  		ret = crypto_skcipher_encrypt(req);
>>  		skcipher_request_zero(req);
>>  	} else {
>> -		preempt_disable();
>> -		pagefault_disable();
>> -		enable_kernel_vsx();
>> -
>>  		blkcipher_walk_init(&walk, dst, src, nbytes);
>>  		ret = blkcipher_walk_virt(desc, &walk);
>>  		while ((nbytes = walk.nbytes)) {
>> +			preempt_disable();
>> +			pagefault_disable();
>> +			enable_kernel_vsx();
>>  			aes_p8_cbc_encrypt(walk.src.virt.addr,
>>  					   walk.dst.virt.addr,
>>  					   nbytes & AES_BLOCK_MASK,
>>  					   &ctx->enc_key, walk.iv, 1);
>> +			disable_kernel_vsx();
>> +			pagefault_enable();
>> +			preempt_enable();
>> +
>>  			nbytes &= AES_BLOCK_SIZE - 1;
>>  			ret = blkcipher_walk_done(desc, &walk, nbytes);
>>  		}
>> -
>> -		disable_kernel_vsx();
>> -		pagefault_enable();
>> -		preempt_enable();
>>  	}
>> 
>>  	return ret;
>> @@ -147,24 +146,23 @@ static int p8_aes_cbc_decrypt(struct 
>> blkcipher_desc *desc,
>>  		ret = crypto_skcipher_decrypt(req);
>>  		skcipher_request_zero(req);
>>  	} else {
>> -		preempt_disable();
>> -		pagefault_disable();
>> -		enable_kernel_vsx();
>> -
>>  		blkcipher_walk_init(&walk, dst, src, nbytes);
>>  		ret = blkcipher_walk_virt(desc, &walk);
>>  		while ((nbytes = walk.nbytes)) {
>> +			preempt_disable();
>> +			pagefault_disable();
>> +			enable_kernel_vsx();
>>  			aes_p8_cbc_encrypt(walk.src.virt.addr,
>>  					   walk.dst.virt.addr,
>>  					   nbytes & AES_BLOCK_MASK,
>>  					   &ctx->dec_key, walk.iv, 0);
>> +			disable_kernel_vsx();
>> +			pagefault_enable();
>> +			preempt_enable();
>> +
>>  			nbytes &= AES_BLOCK_SIZE - 1;
>>  			ret = blkcipher_walk_done(desc, &walk, nbytes);
>>  		}
>> -
>> -		disable_kernel_vsx();
>> -		pagefault_enable();
>> -		preempt_enable();
>>  	}
>> 
>>  	return ret;
>> diff --git a/drivers/crypto/vmx/aes_xts.c 
>> b/drivers/crypto/vmx/aes_xts.c
>> index 8bd9aff0f55f..e9954a7d4694 100644
>> --- a/drivers/crypto/vmx/aes_xts.c
>> +++ b/drivers/crypto/vmx/aes_xts.c
>> @@ -116,32 +116,39 @@ static int p8_aes_xts_crypt(struct 
>> blkcipher_desc *desc,
>>  		ret = enc? crypto_skcipher_encrypt(req) : 
>> crypto_skcipher_decrypt(req);
>>  		skcipher_request_zero(req);
>>  	} else {
>> +		blkcipher_walk_init(&walk, dst, src, nbytes);
>> +
>> +		ret = blkcipher_walk_virt(desc, &walk);
>> +
>>  		preempt_disable();
>>  		pagefault_disable();
>>  		enable_kernel_vsx();
>> 
>> -		blkcipher_walk_init(&walk, dst, src, nbytes);
>> -
>> -		ret = blkcipher_walk_virt(desc, &walk);
>>  		iv = walk.iv;
>>  		memset(tweak, 0, AES_BLOCK_SIZE);
>>  		aes_p8_encrypt(iv, tweak, &ctx->tweak_key);
>> 
>> +		disable_kernel_vsx();
>> +		pagefault_enable();
>> +		preempt_enable();
>> +
>>  		while ((nbytes = walk.nbytes)) {
>> +			preempt_disable();
>> +			pagefault_disable();
>> +			enable_kernel_vsx();
>>  			if (enc)
>>  				aes_p8_xts_encrypt(walk.src.virt.addr, walk.dst.virt.addr,
>>  						nbytes & AES_BLOCK_MASK, &ctx->enc_key, NULL, tweak);
>>  			else
>>  				aes_p8_xts_decrypt(walk.src.virt.addr, walk.dst.virt.addr,
>>  						nbytes & AES_BLOCK_MASK, &ctx->dec_key, NULL, tweak);
>> +			disable_kernel_vsx();
>> +			pagefault_enable();
>> +			preempt_enable();
>> 
>>  			nbytes &= AES_BLOCK_SIZE - 1;
>>  			ret = blkcipher_walk_done(desc, &walk, nbytes);
>>  		}
>> -
>> -		disable_kernel_vsx();
>> -		pagefault_enable();
>> -		preempt_enable();
>>  	}
>>  	return ret;
>>  }
>> --
>> 2.17.1
>> 

Sure thing. I'll test it later today. Thanks Ondrej for the fix.

-- 
Paulo Flabiano Smorigo
IBM Linux Technology Center