[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging-4.16] x86/mm: correct TLB flush condition in _get_page_type()
commit 221f6a97b59e008f11eb310ad0c9b802f3bea233 Author: Jan Beulich <jbeulich@xxxxxxxx> AuthorDate: Tue Jul 26 14:59:07 2022 +0200 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Tue Jul 26 14:59:07 2022 +0200 x86/mm: correct TLB flush condition in _get_page_type() When this logic was moved, it was moved across the point where nx is updated to hold the new type for the page. IOW originally it was equivalent to using x (and perhaps x would better have been used), but now it isn't anymore. Switch to using x, which then brings things in line again with the slightly earlier comment there (now) talking about transitions _from_ writable. I have to confess though that I cannot make a direct connection between the reported observed behavior of guests leaving several pages around with pending general references and the change here. Repeated testing, nevertheless, confirms the reported issue is no longer there. This is CVE-2022-33745 / XSA-408. Reported-by: Charles Arnold <carnold@xxxxxxxx> Fixes: 8cc5036bc385 ("x86/pv: Fix ABAC cmpxchg() race in _get_page_type()") Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> master commit: a9949efb288fd6e21bbaf9d5826207c7c41cda27 master date: 2022-07-26 14:54:34 +0200 --- xen/arch/x86/mm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index c1b9a3bb10..5812321cae 100644 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -3004,7 +3004,7 @@ static int _get_page_type(struct page_info *page, unsigned long type, if ( unlikely(!cpumask_empty(mask)) && /* Shadow mode: track only writable pages. */ (!shadow_mode_enabled(d) || - ((nx & PGT_type_mask) == PGT_writable_page)) ) + ((x & PGT_type_mask) == PGT_writable_page)) ) { perfc_incr(need_flush_tlb_flush); /* -- generated by git-patchbot for /home/xen/git/xen.git#staging-4.16
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