2022-02-02 11:36:40

by Oded Gabbay

Subject: Re: [PATCH] habanalabs: fix potential spectre v1 gadgets

On Wed, Feb 2, 2022 at 9:50 AM Oded Gabbay <[email protected]> wrote:
>
> On Tue, Feb 1, 2022 at 7:25 PM Jordy Zomer <[email protected]> wrote:
> >
> > It appears like nr could be a Spectre v1 gadget as it's supplied by a
> > user and used as an array index. Prevent the contents
> > of kernel memory from being leaked to userspace via speculative
> > execution by using array_index_nospec.
> >
> > Signed-off-by: Jordy Zomer <[email protected]>
> > ---
> > drivers/misc/habanalabs/common/habanalabs_ioctl.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/misc/habanalabs/common/habanalabs_ioctl.c b/drivers/misc/habanalabs/common/habanalabs_ioctl.c
> > index 3ba3a8ffda3e..c1cdf712a10d 100644
> > --- a/drivers/misc/habanalabs/common/habanalabs_ioctl.c
> > +++ b/drivers/misc/habanalabs/common/habanalabs_ioctl.c
> > @@ -14,6 +14,7 @@
> > #include <linux/fs.h>
> > #include <linux/uaccess.h>
> > #include <linux/slab.h>
> > +#include <linux/nospec.h>
> >
> > static u32 hl_debug_struct_size[HL_DEBUG_OP_TIMESTAMP + 1] = {
> > [HL_DEBUG_OP_ETR] = sizeof(struct hl_debug_params_etr),
> > @@ -849,6 +850,7 @@ long hl_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
> > }
> >
> > if ((nr >= HL_COMMAND_START) && (nr < HL_COMMAND_END)) {
> > + nr = array_index_nospec(nr, HL_COMMAND_END-1);
This needs to be HL_COMMAND_END.
The pattern (as described in array_index_nospec comment) is
if (index < size) {
index = array_index_nospec(index, size);
val = array[index];
}

When you do -1, it misses the last value which causes that ioctl to
get rejected.

> > ioctl = &hl_ioctls[nr];
> > } else {
> > dev_err(hdev->dev, "invalid ioctl: pid=%d, nr=0x%02x\n",
> > @@ -872,6 +874,7 @@ long hl_ioctl_control(struct file *filep, unsigned int cmd, unsigned long arg)
> > }
> >
> > if (nr == _IOC_NR(HL_IOCTL_INFO)) {
> > + nr = array_index_nospec(nr, _IOC_NR(HL_IOCTL_INFO));
same here, it should be _IOC_NR(HL_IOCTL_INFO) + 1

Thanks,
Oded

> > ioctl = &hl_ioctls_control[nr];
> > } else {
> > dev_err(hdev->dev_ctrl, "invalid ioctl: pid=%d, nr=0x%02x\n",
> > --
> > 2.27.0
> >
>
> Thanks for the patch.
> I'm going to run this through our CI and if nothing breaks I'll merge
> it to our -next branch.
>
> Oded

2022-02-03 20:33:10

by Jordy Zomer

Subject: [PATCHv2] habanalabs: fix potential spectre v1 gadgets

It appears like nr could be a Spectre v1 gadget as it's supplied by a
user and used as an array index. Prevent the contents
of kernel memory from being leaked to userspace via speculative
execution by using array_index_nospec.

Thanks for noticing Oded, made the changes.

Signed-off-by: Jordy Zomer <[email protected]>

---
Changes v1 -> v2: Added the correct offsets
---
drivers/misc/habanalabs/common/habanalabs_ioctl.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/misc/habanalabs/common/habanalabs_ioctl.c b/drivers/misc/habanalabs/common/habanalabs_ioctl.c
index 3ba3a8ffda3e..c1cdf712a10d 100644
--- a/drivers/misc/habanalabs/common/habanalabs_ioctl.c
+++ b/drivers/misc/habanalabs/common/habanalabs_ioctl.c
@@ -14,6 +14,7 @@
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
+#include <linux/nospec.h>

static u32 hl_debug_struct_size[HL_DEBUG_OP_TIMESTAMP + 1] = {
[HL_DEBUG_OP_ETR] = sizeof(struct hl_debug_params_etr),
@@ -849,6 +850,7 @@ long hl_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
}

if ((nr >= HL_COMMAND_START) && (nr < HL_COMMAND_END)) {
+ nr = array_index_nospec(nr, HL_COMMAND_END);
ioctl = &hl_ioctls[nr];
} else {
dev_err(hdev->dev, "invalid ioctl: pid=%d, nr=0x%02x\n",
@@ -872,6 +874,7 @@ long hl_ioctl_control(struct file *filep, unsigned int cmd, unsigned long arg)
}

if (nr == _IOC_NR(HL_IOCTL_INFO)) {
+ nr = array_index_nospec(nr, _IOC_NR(HL_IOCTL_INFO)+1);
ioctl = &hl_ioctls_control[nr];
} else {
dev_err(hdev->dev_ctrl, "invalid ioctl: pid=%d, nr=0x%02x\n",
--
2.27.0