Commit-ID: e3e288121408c3abeed5af60b87b95c847143845 Gitweb: https://git.kernel.org/tip/e3e288121408c3abeed5af60b87b95c847143845 Author: Joerg Roedel <[email protected]> AuthorDate: Wed, 11 Apr 2018 17:24:38 +0200 Committer: Ingo Molnar <[email protected]> CommitDate: Thu, 12 Apr 2018 09:41:41 +0200
x86/pgtable: Don't set huge PUD/PMD on non-leaf entries The pmd_set_huge() and pud_set_huge() functions are used from the generic ioremap() code to establish large mappings where this is possible. But the generic ioremap() code does not check whether the PMD/PUD entries are already populated with a non-leaf entry, so that any page-table pages these entries point to will be lost. Further, on x86-32 with SHARED_KERNEL_PMD=0, this causes a BUG_ON() in vmalloc_sync_one() when PMD entries are synced from swapper_pg_dir to the current page-table. This happens because the PMD entry from swapper_pg_dir was promoted to a huge-page entry while the current PGD still contains the non-leaf entry. Because both entries are present and point to a different page, the BUG_ON() triggers. This was actually triggered with pti-x32 enabled in a KVM virtual machine by the graphics driver. A real and better fix for that would be to improve the page-table handling in the generic ioremap() code. But that is out-of-scope for this patch-set and left for later work. Reported-by: David H. Gutteridge <[email protected]> Signed-off-by: Joerg Roedel <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Boris Ostrovsky <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Dave Hansen <[email protected]> Cc: David Laight <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: Eduardo Valentin <[email protected]> Cc: Greg KH <[email protected]> Cc: Jiri Kosina <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Juergen Gross <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Pavel Machek <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Waiman Long <[email protected]> Cc: Will Deacon <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/mm/pgtable.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index d10a40aceeaa..ffc8c13c50e4 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/mm.h> #include <linux/gfp.h> +#include <linux/hugetlb.h> #include <asm/pgalloc.h> #include <asm/pgtable.h> #include <asm/tlb.h> @@ -639,6 +640,10 @@ int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot) (mtrr != MTRR_TYPE_WRBACK)) return 0; + /* Bail out if we are we on a populated non-leaf entry: */ + if (pud_present(*pud) && !pud_huge(*pud)) + return 0; + prot = pgprot_4k_2_large(prot); set_pte((pte_t *)pud, pfn_pte( @@ -667,6 +672,10 @@ int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot) return 0; } + /* Bail out if we are we on a populated non-leaf entry: */ + if (pmd_present(*pmd) && !pmd_huge(*pmd)) + return 0; + prot = pgprot_4k_2_large(prot); set_pte((pte_t *)pmd, pfn_pte(
