[2/5] crypto: ccp: Reject SEV commands with mismatching command buffer
diff mbox series

Message ID 20210402233702.3291792-3-seanjc@google.com
State New, archived
Headers show
Series
  • ccp: KVM: SVM: Use stack for SEV command buffers
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Commit Message

Sean Christopherson April 2, 2021, 11:36 p.m. UTC
WARN on and reject SEV commands that provide a valid data pointer, but do
not have a known, non-zero length.  And conversely, reject commands that
take a command buffer but none is provided.

Aside from sanity checking intput, disallowing a non-null pointer without
a non-zero size will allow a future patch to cleanly handle vmalloc'd
data by copying the data to an internal __pa() friendly buffer.

Note, this also effectively prevents callers from using commands that
have a non-zero length and are not known to the kernel.  This is not an
explicit goal, but arguably the side effect is a good thing from the
kernel's perspective.

Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 drivers/crypto/ccp/sev-dev.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

Comments

Christophe Leroy April 3, 2021, 5:02 p.m. UTC | #1
Le 03/04/2021 à 01:36, Sean Christopherson a écrit :
> WARN on and reject SEV commands that provide a valid data pointer, but do
> not have a known, non-zero length.  And conversely, reject commands that
> take a command buffer but none is provided.
> 
> Aside from sanity checking intput, disallowing a non-null pointer without
> a non-zero size will allow a future patch to cleanly handle vmalloc'd
> data by copying the data to an internal __pa() friendly buffer.
> 
> Note, this also effectively prevents callers from using commands that
> have a non-zero length and are not known to the kernel.  This is not an
> explicit goal, but arguably the side effect is a good thing from the
> kernel's perspective.
> 
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>   drivers/crypto/ccp/sev-dev.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 6556d220713b..4c513318f16a 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -141,6 +141,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>   	struct sev_device *sev;
>   	unsigned int phys_lsb, phys_msb;
>   	unsigned int reg, ret = 0;
> +	int buf_len;
>   
>   	if (!psp || !psp->sev_data)
>   		return -ENODEV;
> @@ -150,7 +151,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>   
>   	sev = psp->sev_data;
>   
> -	if (data && WARN_ON_ONCE(is_vmalloc_addr(data)))
> +	buf_len = sev_cmd_buffer_len(cmd);
> +	if (WARN_ON_ONCE(!!data != !!buf_len))
> +		return -EINVAL;
> +
> +	if (WARN_ON_ONCE(data && is_vmalloc_addr(data)))

Shouldn't it be !virt_addr_valid() instead of is_vmalloc_addr() ?


>   		return -EINVAL;
>   
>   	/* Get the physical address of the command buffer */
> @@ -161,7 +166,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>   		cmd, phys_msb, phys_lsb, psp_timeout);
>   
>   	print_hex_dump_debug("(in):  ", DUMP_PREFIX_OFFSET, 16, 2, data,
> -			     sev_cmd_buffer_len(cmd), false);
> +			     buf_len, false);
>   
>   	iowrite32(phys_lsb, sev->io_regs + sev->vdata->cmdbuff_addr_lo_reg);
>   	iowrite32(phys_msb, sev->io_regs + sev->vdata->cmdbuff_addr_hi_reg);
> @@ -197,7 +202,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>   	}
>   
>   	print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
> -			     sev_cmd_buffer_len(cmd), false);
> +			     buf_len, false);
>   
>   	return ret;
>   }
>
Tom Lendacky April 5, 2021, 4:26 p.m. UTC | #2
On 4/2/21 6:36 PM, Sean Christopherson wrote:
> WARN on and reject SEV commands that provide a valid data pointer, but do
> not have a known, non-zero length.  And conversely, reject commands that
> take a command buffer but none is provided.
> 
> Aside from sanity checking intput, disallowing a non-null pointer without

s/intput/input/

> a non-zero size will allow a future patch to cleanly handle vmalloc'd
> data by copying the data to an internal __pa() friendly buffer.
> 
> Note, this also effectively prevents callers from using commands that
> have a non-zero length and are not known to the kernel.  This is not an
> explicit goal, but arguably the side effect is a good thing from the
> kernel's perspective.
> 
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  drivers/crypto/ccp/sev-dev.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 6556d220713b..4c513318f16a 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -141,6 +141,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>  	struct sev_device *sev;
>  	unsigned int phys_lsb, phys_msb;
>  	unsigned int reg, ret = 0;
> +	int buf_len;
>  
>  	if (!psp || !psp->sev_data)
>  		return -ENODEV;
> @@ -150,7 +151,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>  
>  	sev = psp->sev_data;
>  
> -	if (data && WARN_ON_ONCE(is_vmalloc_addr(data)))
> +	buf_len = sev_cmd_buffer_len(cmd);
> +	if (WARN_ON_ONCE(!!data != !!buf_len))

Seems a bit confusing to me.  Can this just be:

	if (WARN_ON_ONCE(data && !buf_len))

Or is this also trying to catch the case where buf_len is non-zero but
data is NULL?

Thanks,
Tom

> +		return -EINVAL;
> +
> +	if (WARN_ON_ONCE(data && is_vmalloc_addr(data)))
>  		return -EINVAL;
>  
>  	/* Get the physical address of the command buffer */
> @@ -161,7 +166,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>  		cmd, phys_msb, phys_lsb, psp_timeout);
>  
>  	print_hex_dump_debug("(in):  ", DUMP_PREFIX_OFFSET, 16, 2, data,
> -			     sev_cmd_buffer_len(cmd), false);
> +			     buf_len, false);
>  
>  	iowrite32(phys_lsb, sev->io_regs + sev->vdata->cmdbuff_addr_lo_reg);
>  	iowrite32(phys_msb, sev->io_regs + sev->vdata->cmdbuff_addr_hi_reg);
> @@ -197,7 +202,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>  	}
>  
>  	print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
> -			     sev_cmd_buffer_len(cmd), false);
> +			     buf_len, false);
>  
>  	return ret;
>  }
>
Sean Christopherson April 5, 2021, 4:33 p.m. UTC | #3
On Mon, Apr 05, 2021, Tom Lendacky wrote:
> On 4/2/21 6:36 PM, Sean Christopherson wrote:
> > diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> > index 6556d220713b..4c513318f16a 100644
> > --- a/drivers/crypto/ccp/sev-dev.c
> > +++ b/drivers/crypto/ccp/sev-dev.c
> > @@ -141,6 +141,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
> >  	struct sev_device *sev;
> >  	unsigned int phys_lsb, phys_msb;
> >  	unsigned int reg, ret = 0;
> > +	int buf_len;
> >  
> >  	if (!psp || !psp->sev_data)
> >  		return -ENODEV;
> > @@ -150,7 +151,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
> >  
> >  	sev = psp->sev_data;
> >  
> > -	if (data && WARN_ON_ONCE(is_vmalloc_addr(data)))
> > +	buf_len = sev_cmd_buffer_len(cmd);
> > +	if (WARN_ON_ONCE(!!data != !!buf_len))
> 
> Seems a bit confusing to me.  Can this just be:
> 
> 	if (WARN_ON_ONCE(data && !buf_len))

Or as Christophe pointed out, "!data != !buf_len".

> Or is this also trying to catch the case where buf_len is non-zero but
> data is NULL?

Ya.  It's not necessary to detect "buf_len && !data", but it doesn't incur
additional cost.  Is there a reason _not_ to disallow that?
Tom Lendacky April 5, 2021, 4:37 p.m. UTC | #4
On 4/5/21 11:33 AM, Sean Christopherson wrote:
> On Mon, Apr 05, 2021, Tom Lendacky wrote:
>> On 4/2/21 6:36 PM, Sean Christopherson wrote:
>>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>>> index 6556d220713b..4c513318f16a 100644
>>> --- a/drivers/crypto/ccp/sev-dev.c
>>> +++ b/drivers/crypto/ccp/sev-dev.c
>>> @@ -141,6 +141,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>>>  	struct sev_device *sev;
>>>  	unsigned int phys_lsb, phys_msb;
>>>  	unsigned int reg, ret = 0;
>>> +	int buf_len;
>>>  
>>>  	if (!psp || !psp->sev_data)
>>>  		return -ENODEV;
>>> @@ -150,7 +151,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>>>  
>>>  	sev = psp->sev_data;
>>>  
>>> -	if (data && WARN_ON_ONCE(is_vmalloc_addr(data)))
>>> +	buf_len = sev_cmd_buffer_len(cmd);
>>> +	if (WARN_ON_ONCE(!!data != !!buf_len))
>>
>> Seems a bit confusing to me.  Can this just be:
>>
>> 	if (WARN_ON_ONCE(data && !buf_len))
> 
> Or as Christophe pointed out, "!data != !buf_len".
> 
>> Or is this also trying to catch the case where buf_len is non-zero but
>> data is NULL?
> 
> Ya.  It's not necessary to detect "buf_len && !data", but it doesn't incur
> additional cost.  Is there a reason _not_ to disallow that?

Nope, no reason. I was just trying to process all the not signs :)

Thanks,
Tom

>

Patch
diff mbox series

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 6556d220713b..4c513318f16a 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -141,6 +141,7 @@  static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 	struct sev_device *sev;
 	unsigned int phys_lsb, phys_msb;
 	unsigned int reg, ret = 0;
+	int buf_len;
 
 	if (!psp || !psp->sev_data)
 		return -ENODEV;
@@ -150,7 +151,11 @@  static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 
 	sev = psp->sev_data;
 
-	if (data && WARN_ON_ONCE(is_vmalloc_addr(data)))
+	buf_len = sev_cmd_buffer_len(cmd);
+	if (WARN_ON_ONCE(!!data != !!buf_len))
+		return -EINVAL;
+
+	if (WARN_ON_ONCE(data && is_vmalloc_addr(data)))
 		return -EINVAL;
 
 	/* Get the physical address of the command buffer */
@@ -161,7 +166,7 @@  static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 		cmd, phys_msb, phys_lsb, psp_timeout);
 
 	print_hex_dump_debug("(in):  ", DUMP_PREFIX_OFFSET, 16, 2, data,
-			     sev_cmd_buffer_len(cmd), false);
+			     buf_len, false);
 
 	iowrite32(phys_lsb, sev->io_regs + sev->vdata->cmdbuff_addr_lo_reg);
 	iowrite32(phys_msb, sev->io_regs + sev->vdata->cmdbuff_addr_hi_reg);
@@ -197,7 +202,7 @@  static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 	}
 
 	print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
-			     sev_cmd_buffer_len(cmd), false);
+			     buf_len, false);
 
 	return ret;
 }