From 53f01e2004ae862f76240c7d92a59fa00a7bfa96 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 29 Aug 2018 08:47:18 -0700 Subject: x86/nmi: Fix NMI uaccess race against CR3 switching commit 4012e77a903d114f915fc607d6d2ed54a3d6c9b1 upstream. A NMI can hit in the middle of context switching or in the middle of switch_mm_irqs_off(). In either case, CR3 might not match current->mm, which could cause copy_from_user_nmi() and friends to read the wrong memory. Fix it by adding a new nmi_uaccess_okay() helper and checking it in copy_from_user_nmi() and in __copy_from_user_nmi()'s callers. Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Reviewed-by: Rik van Riel Cc: Nadav Amit Cc: Borislav Petkov Cc: Jann Horn Cc: Peter Zijlstra Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/dd956eba16646fd0b15c3c0741269dfd84452dac.1535557289.git.luto@kernel.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/lib/usercopy.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'arch/x86/lib') diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c index c8c6ad0d58b8..3f435d7fca5e 100644 --- a/arch/x86/lib/usercopy.c +++ b/arch/x86/lib/usercopy.c @@ -7,6 +7,8 @@ #include #include +#include + /* * We rely on the nested NMI work to allow atomic faults from the NMI path; the * nested NMI paths are careful to preserve CR2. @@ -19,6 +21,9 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n) if (__range_not_ok(from, n, TASK_SIZE)) return n; + if (!nmi_uaccess_okay()) + return n; + /* * Even though this function is typically called from NMI/IRQ context * disable pagefaults so that its behaviour is consistent even when -- cgit v1.2.3