Kernel/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2025-01-07 13:43:51 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

KVM: Check validity of resolved slot when searching memslots

Browse Source 
Check that the resolved slot (somewhat confusingly named 'start') is a
valid/allocated slot before doing the final comparison to see if the
specified gfn resides in the associated slot.  The resolved slot can be
invalid if the binary search loop terminated because the search index
was incremented beyond the number of used slots.

This bug has existed since the binary search algorithm was introduced,
but went unnoticed because KVM statically allocated memory for the max
number of slots, i.e. the access would only be truly out-of-bounds if
all possible slots were allocated and the specified gfn was less than
the base of the lowest memslot.  Commit 36947254e5 ("KVM: Dynamically
size memslot array based on number of used slots") eliminated the "all
possible slots allocated" condition and made the bug embarrasingly easy
to hit.

Fixes: 9c1a5d3878 ("kvm: optimize GFN to memslot lookup with large slots amount")
Reported-by: syzbot+d889b59b2bb87d4047a2@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200408064059.8957-2-sean.j.christopherson@intel.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-04-07 23:40:58 -07:00 committed by Paolo Bonzini
parent fb56baae5e
commit b6467ab142
1 changed files with 1 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/kvm_host.h
View File

@ -1048,7 +1048,7 @@ search_memslots(struct kvm_memslots *slots, gfn_t gfn)
start = slot + 1;
}
if (gfn >= memslots[start].base_gfn &&
if (start < slots->used_slots && gfn >= memslots[start].base_gfn &&
gfn < memslots[start].base_gfn + memslots[start].npages) {
atomic_set(&slots->lru_slot, start);
return &memslots[start];