From: Peter Gonda <pgonda@google.com>
Date: Wed, 27 Jan 2021 08:15:24 -0800
Subject: Fix unsynchronized access to sev members through
svm_register_enc_region
Git-commit: 19a23da53932bc8011220bd8c410cb76012de004
Patch-mainline: v5.11-rc7
References: bsc#1114648
Grab kvm->lock before pinning memory when registering an encrypted
region; sev_pin_memory() relies on kvm->lock being held to ensure
correctness when checking and updating the number of pinned pages.
Add a lockdep assertion to help prevent future regressions.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: stable@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Fixes: 1e80fdc09d12 ("KVM: SVM: Pin guest memory when SEV is active")
Signed-off-by: Peter Gonda <pgonda@google.com>
V2
- Fix up patch description
- Correct file paths svm.c -> sev.c
- Add unlock of kvm->lock on sev_pin_memory error
V1
- https://lore.kernel.org/kvm/20210126185431.1824530-1-pgonda@google.com/
Message-Id: <20210127161524.2832400-1-pgonda@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kvm/svm.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1791,6 +1791,8 @@ static struct page **sev_pin_memory(stru
struct page **pages;
int first, last;
+ lockdep_assert_held(&kvm->lock);
+
/* Calculate number of pages. */
first = (uaddr & PAGE_MASK) >> PAGE_SHIFT;
last = ((uaddr + ulen - 1) & PAGE_MASK) >> PAGE_SHIFT;
@@ -7019,12 +7021,20 @@ static int svm_register_enc_region(struc
if (!region)
return -ENOMEM;
+ mutex_lock(&kvm->lock);
region->pages = sev_pin_memory(kvm, range->addr, range->size, ®ion->npages, 1);
if (!region->pages) {
ret = -ENOMEM;
+ mutex_unlock(&kvm->lock);
goto e_free;
}
+ region->uaddr = range->addr;
+ region->size = range->size;
+
+ list_add_tail(®ion->list, &sev->regions_list);
+ mutex_unlock(&kvm->lock);
+
/*
* The guest may change the memory encryption attribute from C=0 -> C=1
* or vice versa for this memory range. Lets make sure caches are
@@ -7033,13 +7043,6 @@ static int svm_register_enc_region(struc
*/
sev_clflush_pages(region->pages, region->npages);
- region->uaddr = range->addr;
- region->size = range->size;
-
- mutex_lock(&kvm->lock);
- list_add_tail(®ion->list, &sev->regions_list);
- mutex_unlock(&kvm->lock);
-
return ret;
e_free: