x86/mm/pti: Add an overflow check to pti_clone_pmds()

[ Upstream commit 935232ce28dfabff1171e5a7113b2d865fa9ee63 ]

The addr counter will overflow if the last PMD of the address space is
cloned, resulting in an endless loop.

Check for that and bail out of the loop when it happens.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Pavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-25-git-send-email-joro@8bytes.org
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index ffa2f0f67904c5123b7b356f862ec2eaeaadfc2c..1d2106d83b4ef8d1973535f30ccdc349046e1d9f 100644 (file)
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -306,6 +306,10 @@ pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear)
                p4d_t *p4d;
                pud_t *pud;
 
+               /* Overflow check */
+               if (addr < start)
+                       break;
+
                pgd = pgd_offset_k(addr);
                if (WARN_ON(pgd_none(*pgd)))
                        return;