On 4/17/19 3:49 AM, David Hildenbrand wrote:
On 17.04.19 02:54, Eric Farman wrote:
Fix some warnings from smatch:
arch/s390/kvm/interrupt.c:2310 get_io_adapter() warn: potential spectre issue 'kvm->arch.adapters' [r] (local cap)
arch/s390/kvm/interrupt.c:2341 register_io_adapter() warn: potential spectre issue 'dev->kvm->arch.adapters' [w]
Signed-off-by: Eric Farman <farman@xxxxxxxxxxxxx>
---
A recent patch from Paolo [1] acted as a reminder (thanks, Christian!)
that I had one for the s390 KVM code after some code reviews [2].
Let's clean that up.
[1] https://patchwork.kernel.org/patch/10895463/
[2] https://patchwork.kernel.org/patch/10788565/#22484223
---
arch/s390/kvm/interrupt.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 82162867f378..bfd55ad34a3e 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -14,6 +14,7 @@
#include <linux/kvm_host.h>
#include <linux/hrtimer.h>
#include <linux/mmu_context.h>
+#include <linux/nospec.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/bitmap.h>
@@ -2307,6 +2308,7 @@ static struct s390_io_adapter *get_io_adapter(struct kvm *kvm, unsigned int id)
{
if (id >= MAX_S390_IO_ADAPTERS)
return NULL;
+ id = array_index_nospec(id, MAX_S390_IO_ADAPTERS);
return kvm->arch.adapters[id];
return kvm->arch.adapters[array_index_nospec(id, MAX_S390_IO_ADAPTERS)];
should exactly fit into a single line if I am not wrong.
Yeah, just. As Paolo pointed out, that's not common usage. Though of
the four other hits I see, only one of them is the same as this
instance, in that "id" is passed as a variable and then we immediately
return with an array entry (even if NULL) rather than doing something
else in that function. So maybe all-in-one-line here is a little cleaner.
}
@@ -2320,8 +2322,13 @@ static int register_io_adapter(struct kvm_device *dev,
(void __user *)attr->addr, sizeof(adapter_info)))
return -EFAULT;
- if ((adapter_info.id >= MAX_S390_IO_ADAPTERS) ||
- (dev->kvm->arch.adapters[adapter_info.id] != NULL))
+ if (adapter_info.id >= MAX_S390_IO_ADAPTERS)
+ return -EINVAL;
+
+ adapter_info.id = array_index_nospec(adapter_info.id,
+ MAX_S390_IO_ADAPTERS);
I dislike that we are modifying adapter_info here. Can you use a local
variable instead?
I guess, but adapter_info is a local variable too. So sanitization this
way seems fine to me. But if you dislike it more than I don't care,
I'll add another local variable. :)
+
+ if (dev->kvm->arch.adapters[adapter_info.id] != NULL)
return -EINVAL;
adapter = kzalloc(sizeof(*adapter), GFP_KERNEL);
