[xen stable-4.17] x86/HVM: bound number of pinned cache attribute regions

[patchbot@xxxxxxx]

commit d0cb66d59a956ccba3dbe794f4ec01e4a4269ee9
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Mar 21 12:01:01 2023 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Mar 21 12:07:42 2023 +0000

    x86/HVM: bound number of pinned cache attribute regions
    
    This is exposed via DMOP, i.e. to potentially not fully privileged
    device models. With that we may not permit registration of an (almost)
    unbounded amount of such regions.
    
    This is CVE-2022-42333 / part of XSA-428.
    
    Fixes: 642123c5123f ("x86/hvm: provide XEN_DMOP_pin_memory_cacheattr")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    (cherry picked from commit a5e768640f786b681063f4e08af45d0c4e91debf)
---
 xen/arch/x86/hvm/mtrr.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/xen/arch/x86/hvm/mtrr.c b/xen/arch/x86/hvm/mtrr.c
index 4d2aa6def8..714911dd7f 100644
--- a/xen/arch/x86/hvm/mtrr.c
+++ b/xen/arch/x86/hvm/mtrr.c
@@ -595,6 +595,7 @@ int hvm_set_mem_pinned_cacheattr(struct domain *d, uint64_t 
gfn_start,
                                  uint64_t gfn_end, uint32_t type)
 {
     struct hvm_mem_pinned_cacheattr_range *range;
+    unsigned int nr = 0;
     int rc = 1;
 
     if ( !is_hvm_domain(d) )
@@ -666,11 +667,15 @@ int hvm_set_mem_pinned_cacheattr(struct domain *d, 
uint64_t gfn_start,
             rc = -EBUSY;
             break;
         }
+        ++nr;
     }
     rcu_read_unlock(&pinned_cacheattr_rcu_lock);
     if ( rc <= 0 )
         return rc;
 
+    if ( nr >= 64 /* The limit is arbitrary. */ )
+        return -ENOSPC;
+
     range = xzalloc(struct hvm_mem_pinned_cacheattr_range);
     if ( range == NULL )
         return -ENOMEM;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.17