Re: [PATCH V2] x86/sev-es: Fix SEV-ES #VC handler for string port IO
On Mon, Jan 11, 2021 at 12:29:08PM -0600, Tom Lendacky wrote: > Shouldn't this have a Fixes: tag? Yah, moving to x86/urgent after a quick IRC clarification. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
Re: [PATCH V2] x86/sev-es: Fix SEV-ES #VC handler for string port IO
On Mon, 11 Jan 2021, Tom Lendacky 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
> > Acked-by: David Rientjes
> > ---
> >
> > This patch is tested by invoking INSB/OUTSB instructions in kernel space in
> > a
> > SEV-ES-enabled VM. Without the patch, the kernel crashed with the following
> > message:
> >"SEV-ES: Unsupported exception in #VC instruction emulation - can't
> > continue"
> > With the patch, the instructions successfully read/wrote the string from/to
> > the I/O port.
>
> Shouldn't this have a Fixes: tag?
>
Makes sense, I think this should likely be:
Fixes: f980f9c31a92 ("x86/sev-es: Compile early handler code into kernel image")
Re: [PATCH V2] x86/sev-es: Fix SEV-ES #VC handler for string port IO
On 1/10/21 1:11 AM, 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
Acked-by: David Rientjes
---
This patch is tested by invoking INSB/OUTSB instructions in kernel space in a
SEV-ES-enabled VM. Without the patch, the kernel crashed with the following
message:
"SEV-ES: Unsupported exception in #VC instruction emulation - can't continue"
With the patch, the instructions successfully read/wrote the string from/to
the I/O port.
Shouldn't this have a Fixes: tag?
Thanks,
Tom
arch/x86/kernel/sev-es.c | 12
1 file changed, 12 insertions(+)
[PATCH V2] 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
Acked-by: David Rientjes
---
This patch is tested by invoking INSB/OUTSB instructions in kernel space in a
SEV-ES-enabled VM. Without the patch, the kernel crashed with the following
message:
"SEV-ES: Unsupported exception in #VC instruction emulation - can't continue"
With the patch, the instructions successfully read/wrote the string from/to
the I/O port.
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..ab31c34ba508 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(target, 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))
--
2.30.0.284.gd98b1dd5eaa7-goog
