2021-01-08 02:55:48

by Hyunwook (Wooky) Baek

Subject: [PATCH] x86/sev-es: Fix SEV-ES #VC handler for string port IO

Don't assume dest/source buffers are userspace addresses when manually
copying data for string I/O or MOVS MMIO, as {get,put}_user() will fail
if handed a kernel address and ultimately lead to a kernel panic.

Signed-off-by: Hyunwook (Wooky) Baek <[email protected]>
Acked-by: David Rientjes <[email protected]>
---
arch/x86/kernel/sev-es.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 0bd1a0fc587e..812494d216ba 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -286,6 +286,12 @@ static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
u16 d2;
u8 d1;

+ /* If instruction ran in kernel mode and the I/O buffer is in kernel space */
+ if (!user_mode(ctxt->regs) && !access_ok(s, size)) {
+ memcpy(dst, buf, size);
+ return ES_OK;
+ }
+
switch (size) {
case 1:
memcpy(&d1, buf, 1);
@@ -335,6 +341,12 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
u16 d2;
u8 d1;

+ /* If instruction ran in kernel mode and the I/O buffer is in kernel space */
+ if (!user_mode(ctxt->regs) && !access_ok(s, size)) {
+ memcpy(buf, src, size);
+ return ES_OK;
+ }
+
switch (size) {
case 1:
if (get_user(d1, s))
--
2.29.2.729.g45daf8777d-goog

2021-01-08 17:23:48

by Borislav Petkov

Subject: Re: [PATCH] x86/sev-es: Fix SEV-ES #VC handler for string port IO

On Thu, Jan 07, 2021 at 06:51:07PM -0800, Hyunwook (Wooky) Baek wrote:
> Don't assume dest/source buffers are userspace addresses when manually
> copying data for string I/O or MOVS MMIO, as {get,put}_user() will fail
> if handed a kernel address and ultimately lead to a kernel panic.
>
> Signed-off-by: Hyunwook (Wooky) Baek <[email protected]>
> Acked-by: David Rientjes <[email protected]>
> ---
> arch/x86/kernel/sev-es.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
> index 0bd1a0fc587e..812494d216ba 100644
> --- a/arch/x86/kernel/sev-es.c
> +++ b/arch/x86/kernel/sev-es.c
> @@ -286,6 +286,12 @@ static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
> u16 d2;
> u8 d1;
>
> + /* If instruction ran in kernel mode and the I/O buffer is in kernel space */
> + if (!user_mode(ctxt->regs) && !access_ok(s, size)) {
^^^

Just by looking at this patch I know you haven't tested it before sending.

:-(

--
Regards/Gruss,
Boris.

https://people.kernel.org/tglx/notes-about-netiquette

2021-01-08 19:35:16

by Hyunwook (Wooky) Baek

Subject: Re: [PATCH] x86/sev-es: Fix SEV-ES #VC handler for string port IO

Hi Borisslav,

My sincere apologies for it.
We actually tested the patch but I made a bad mistake while generating
the patch file to email.
I will send a PATCH V2 after testing the email version patch file from
the scratch.

Regards,
Wooky

On Fri, Jan 8, 2021 at 9:20 AM Borislav Petkov <[email protected]> wrote:
>
> On Thu, Jan 07, 2021 at 06:51:07PM -0800, Hyunwook (Wooky) Baek wrote:
> > Don't assume dest/source buffers are userspace addresses when manually
> > copying data for string I/O or MOVS MMIO, as {get,put}_user() will fail
> > if handed a kernel address and ultimately lead to a kernel panic.
> >
> > Signed-off-by: Hyunwook (Wooky) Baek <[email protected]>
> > Acked-by: David Rientjes <[email protected]>
> > ---
> > arch/x86/kernel/sev-es.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
> > index 0bd1a0fc587e..812494d216ba 100644
> > --- a/arch/x86/kernel/sev-es.c
> > +++ b/arch/x86/kernel/sev-es.c
> > @@ -286,6 +286,12 @@ static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
> > u16 d2;
> > u8 d1;
> >
> > + /* If instruction ran in kernel mode and the I/O buffer is in kernel space */
> > + if (!user_mode(ctxt->regs) && !access_ok(s, size)) {
> ^^^
>
> Just by looking at this patch I know you haven't tested it before sending.
>
> :-(
>
> --
> Regards/Gruss,
> Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette