On Mon, May 16, 2022 at 9:02 AM Kalra, Ashish <Ashish.Kalra@xxxxxxx> wrote: > > [AMD Official Use Only - General] > > Hello Peter, > > -----Original Message----- > From: Peter Gonda <pgonda@xxxxxxxxxx> > Sent: Monday, May 16, 2022 10:53 AM > To: Allen, John <John.Allen@xxxxxxx> > Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>; Linux Crypto Mailing List <linux-crypto@xxxxxxxxxxxxxxx>; Sean Christopherson <seanjc@xxxxxxxxxx>; Lendacky, Thomas <Thomas.Lendacky@xxxxxxx>; Kalra, Ashish <Ashish.Kalra@xxxxxxx>; LKML <linux-kernel@xxxxxxxxxxxxxxx>; Andy Nguyen <theflow@xxxxxxxxxx>; David Rientjes <rientjes@xxxxxxxxxx>; stable@xxxxxxxxxxxxxxx > 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@xxxxxxx> 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@xxxxxxxxxxxxxxx > > Reported-by: Andy Nguyen <theflow@xxxxxxxxxx> > > Suggested-by: David Rientjes <rientjes@xxxxxxxxxx> > > Suggested-by: Peter Gonda <pgonda@xxxxxxxxxx> > > Signed-off-by: John Allen <john.allen@xxxxxxx> > > --- > > v2: > > - Add fixes tags and CC stable@xxxxxxxxxxxxxxx > > --- > > > >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