| Message ID | 20171020023413.122280-17-brijesh.singh@amd.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
On Thu, Oct 19, 2017 at 09:33:51PM -0500, Brijesh Singh wrote: > The SEV_PEK_GEN command is used to generate a new Platform Endorsement > Key (PEK). The command is defined in SEV spec section 5.6. > > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: "Radim Krčmář" <rkrcmar@redhat.com> > Cc: Borislav Petkov <bp@suse.de> > Cc: Herbert Xu <herbert@gondor.apana.org.au> > Cc: Gary Hook <gary.hook@amd.com> > Cc: Tom Lendacky <thomas.lendacky@amd.com> > Cc: linux-crypto@vger.kernel.org > Cc: kvm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > --- > drivers/crypto/ccp/psp-dev.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c > index 5c921b36bc23..1d7212da25a5 100644 > --- a/drivers/crypto/ccp/psp-dev.c > +++ b/drivers/crypto/ccp/psp-dev.c > @@ -195,6 +195,24 @@ static int sev_ioctl_do_platform_status(struct sev_issue_cmd *argp) > return ret; > } > > +static int sev_ioctl_do_pek_pdh_gen(int cmd, struct sev_issue_cmd *argp) > +{ > + int ret, err; > + > + ret = sev_platform_init(NULL, &argp->error); > + if (ret) > + return ret; > + > + ret = sev_do_cmd(cmd, 0, &argp->error); So this ret value gets potentially overwritten here. You need to either handle the case properly when sev_do_cmd() fails and sev_platform_shutdown() gets to issue SEV_CMD_SHUTDOWN (i.e., when it gets overwritten), or not write into ret at all by initializing it to 0 at function entry.
On 10/23/17 4:32 AM, Borislav Petkov wrote: ... >> +static int sev_ioctl_do_pek_pdh_gen(int cmd, struct sev_issue_cmd *argp) >> +{ >> + int ret, err; >> + >> + ret = sev_platform_init(NULL, &argp->error); >> + if (ret) >> + return ret; >> + >> + ret = sev_do_cmd(cmd, 0, &argp->error); > So this ret value gets potentially overwritten here. You need > to either handle the case properly when sev_do_cmd() fails and > sev_platform_shutdown() gets to issue SEV_CMD_SHUTDOWN (i.e., when it > gets overwritten), or not write into ret at all by initializing it to 0 > at function entry. > I am not sure if I am able to understand your feedback. The sev_platform_shutdown() is called unconditionally. 1) if sev_do_cmd() fails and sev_platform_shutdown() was success then 'ret' will contain the error code from sev_do_cmd(). 2) if sev_do_cmd() was success but sev_platform_shutdown() fails then 'ret' will contain the error code from sev_platform_shutdown() 3) if both sev_do_cmd() and sev_platform_shutdown() fails then 'ret' will contain error code from the sev_platform_shutdown().
On Mon, Oct 23, 2017 at 07:15:30AM -0500, Brijesh Singh wrote: > I am not sure if I am able to understand your feedback. The > sev_platform_shutdown() is called unconditionally. How's that: If sev_do_cmd() fails and sev_do_cmd(SEV_CMD_SHUTDOWN, ...) in sev_platform_shutdown() fails, then the first ret from sev_do_cmd() is gone.
On 10/23/17 7:32 AM, Borislav Petkov wrote: > On Mon, Oct 23, 2017 at 07:15:30AM -0500, Brijesh Singh wrote: >> I am not sure if I am able to understand your feedback. The >> sev_platform_shutdown() is called unconditionally. > How's that: > > If sev_do_cmd() fails and sev_do_cmd(SEV_CMD_SHUTDOWN, ...) in > sev_platform_shutdown() fails, then the first ret from sev_do_cmd() is > gone. If both the command fails then we return status from the last command. IIRC, in my previous patches I was returning status from sev_do_cmd() instead of sev_platform_shutdown() but based on our previous communication I thought you asked to return the status from the last failed command. Did I miss understood ? -Brijesh
On Mon, Oct 23, 2017 at 08:32:57AM -0500, Brijesh Singh wrote: > If both the command fails then we return status from the last command. > IIRC, in my previous patches I was returning status from sev_do_cmd() > instead of sev_platform_shutdown() but based on our previous > communication I thought you asked to return the status from the last > failed command. Did I miss understood ? So my problem is that it looks strange that you save an error value from sev_do_cmd() but you don't look at it. And as I said in the other mail, you should either ignore it and say so in a comment why it is OK to ignore it or handle it but not overwrite it without looking at it. Does that make more sense?
On 10/23/2017 09:10 AM, Borislav Petkov wrote: > On Mon, Oct 23, 2017 at 08:32:57AM -0500, Brijesh Singh wrote: >> If both the command fails then we return status from the last command. >> IIRC, in my previous patches I was returning status from sev_do_cmd() >> instead of sev_platform_shutdown() but based on our previous >> communication I thought you asked to return the status from the last >> failed command. Did I miss understood ? > > So my problem is that it looks strange that you save an error value from > sev_do_cmd() but you don't look at it. And as I said in the other mail, > you should either ignore it and say so in a comment why it is OK to > ignore it or handle it but not overwrite it without looking at it. > > Does that make more sense? > I see your point, if both commands failed then I am now inclined towards ignoring the error code from shutdown command and add some comments explaining why its OK. thanks -Brijesh
diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c index 5c921b36bc23..1d7212da25a5 100644 --- a/drivers/crypto/ccp/psp-dev.c +++ b/drivers/crypto/ccp/psp-dev.c @@ -195,6 +195,24 @@ static int sev_ioctl_do_platform_status(struct sev_issue_cmd *argp) return ret; } +static int sev_ioctl_do_pek_pdh_gen(int cmd, struct sev_issue_cmd *argp) +{ + int ret, err; + + ret = sev_platform_init(NULL, &argp->error); + if (ret) + return ret; + + ret = sev_do_cmd(cmd, 0, &argp->error); + + if (sev_platform_shutdown(&err)) { + argp->error = err; + ret = -EIO; + } + + return ret; +} + static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg) { void __user *argp = (void __user *)arg; @@ -218,6 +236,9 @@ static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg) case SEV_PLATFORM_STATUS: ret = sev_ioctl_do_platform_status(&input); break; + case SEV_PEK_GEN: + ret = sev_ioctl_do_pek_pdh_gen(SEV_CMD_PEK_GEN, &input); + break; default: ret = -EINVAL; goto out;
The SEV_PEK_GEN command is used to generate a new Platform Endorsement Key (PEK). The command is defined in SEV spec section 5.6. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "Radim Krčmář" <rkrcmar@redhat.com> Cc: Borislav Petkov <bp@suse.de> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Gary Hook <gary.hook@amd.com> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: linux-crypto@vger.kernel.org Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> --- drivers/crypto/ccp/psp-dev.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)