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]>
---
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
The following commit has been merged into the x86/seves branch of tip:
Commit-ID: 36648d64ac3420b3cfa741b12b14633fad9651e4
Gitweb: https://git.kernel.org/tip/36648d64ac3420b3cfa741b12b14633fad9651e4
Author: Hyunwook (Wooky) Baek <[email protected]>
AuthorDate: Sat, 09 Jan 2021 23:11:02 -08:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Mon, 11 Jan 2021 12:22:10 +01:00
x86/sev-es: Handle string port IO to kernel memory properly
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.
When invoking INSB/OUTSB instructions in kernel space in a
SEV-ES-enabled VM, the kernel crashes with the following message:
"SEV-ES: Unsupported exception in #VC instruction emulation - can't continue"
Handle that case properly.
[ bp: Massage commit message. ]
Signed-off-by: Hyunwook (Wooky) Baek <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Acked-by: David Rientjes <[email protected]>
Link: https://lkml.kernel.org/r/[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 0bd1a0f..ab31c34 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))
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 <[email protected]>
> Acked-by: David Rientjes <[email protected]>
> ---
>
> 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(+)
>
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 <[email protected]>
> > Acked-by: David Rientjes <[email protected]>
> > ---
> >
> > 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")
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
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 7024f60d655272bd2ca1d3a4c9e0a63319b1eea1
Gitweb: https://git.kernel.org/tip/7024f60d655272bd2ca1d3a4c9e0a63319b1eea1
Author: Hyunwook (Wooky) Baek <[email protected]>
AuthorDate: Sat, 09 Jan 2021 23:11:02 -08:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Mon, 11 Jan 2021 20:01:52 +01:00
x86/sev-es: Handle string port IO to kernel memory properly
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.
When invoking INSB/OUTSB instructions in kernel space in a
SEV-ES-enabled VM, the kernel crashes with the following message:
"SEV-ES: Unsupported exception in #VC instruction emulation - can't continue"
Handle that case properly.
[ bp: Massage commit message. ]
Fixes: f980f9c31a92 ("x86/sev-es: Compile early handler code into kernel image")
Signed-off-by: Hyunwook (Wooky) Baek <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Acked-by: David Rientjes <[email protected]>
Link: https://lkml.kernel.org/r/[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 0bd1a0f..ab31c34 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))