On Mon, May 16, 2022 at 9:02 AM Kalra, Ashish Ashish.Kalra@amd.com wrote:
[AMD Official Use Only - General]
Hello Peter,
-----Original Message----- From: Peter Gonda pgonda@google.com Sent: Monday, May 16, 2022 10:53 AM To: Allen, John John.Allen@amd.com Cc: Herbert Xu herbert@gondor.apana.org.au; Linux Crypto Mailing List linux-crypto@vger.kernel.org; Sean Christopherson seanjc@google.com; Lendacky, Thomas Thomas.Lendacky@amd.com; Kalra, Ashish Ashish.Kalra@amd.com; LKML linux-kernel@vger.kernel.org; Andy Nguyen theflow@google.com; David Rientjes rientjes@google.com; stable@vger.kernel.org Subject: Re: [PATCH v2] crypto: ccp - Use kzalloc for sev ioctl interfaces to prevent kernel memory leak
On Mon, May 16, 2022 at 8:46 AM John Allen john.allen@amd.com wrote:
For some sev ioctl interfaces, input may be passed that is less than or equal to SEV_FW_BLOB_MAX_SIZE, but larger than the data that PSP firmware returns. In this case, kmalloc will allocate memory that is the size of the input rather than the size of the data. Since PSP firmware doesn't fully overwrite the buffer, the sev ioctl interfaces with the issue may return uninitialized slab memory.
Currently, all of the ioctl interfaces in the ccp driver are safe, but to prevent future problems, change all ioctl interfaces that allocate memory with kmalloc to use kzalloc.
Fixes: e799035609e15 ("crypto: ccp: Implement SEV_PEK_CSR ioctl command") Fixes: 76a2b524a4b1d ("crypto: ccp: Implement SEV_PDH_CERT_EXPORT ioctl command") Fixes: d6112ea0cb344 ("crypto: ccp - introduce SEV_GET_ID2 command") Cc: stable@vger.kernel.org Reported-by: Andy Nguyen theflow@google.com Suggested-by: David Rientjes rientjes@google.com Suggested-by: Peter Gonda pgonda@google.com Signed-off-by: John Allen john.allen@amd.com
v2:
- Add fixes tags and CC stable@vger.kernel.org
static int sev_ioctl_do_platform_status(struct sev_issue_cmd *argp) { struct sev_user_data_status data; int ret;
ret = __sev_do_cmd_locked(SEV_CMD_PLATFORM_STATUS, &data, &argp->error); if (ret) return ret;
if (copy_to_user((void __user *)argp->data, &data, sizeof(data))) ret = -EFAULT;
return ret; }
Would it be safer to memset @data here to all zeros too?
It will be, but this command/function is safe as firmware will fill in the whole buffer here with the PLATFORM STATUS data retuned to the user.
That does seem safe for now but I thought we decided it would be prudent to not trust the PSPs implementation here and clear all the buffers that eventually get sent to userspace?
Thanks, Ashish