George Dunlap
2010-Apr-12 16:05 UTC
[Xen-devel] [PATCH] Fix read-to-use race condition in shadow code
If OOS mode is enabled, after last possible resync, read the guest l1e one last time. If it''s different than the original read, start over again. This fixes a race which can result in inconsistent in-sync shadow tables, leading to corruption: v1: take page fault, read gl1e from an out-of-sync PT. v2: modify gl1e, lowering permissions [v1,v3]: resync l1 which was just read. v1: propagate change to l1 shadow using stale gl1e Now we have an in-sync shadow with more permissions than the guest. The resync can happen either as a result of a 3rd vcpu doing a cr3 update, or under certain conditions by v1 itself. This should probably be back-ported to 3.4.x and 4.0.x. Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel