Commit-ID: 360cb4d15567a7eca07a5f3ade6de308bbfb4e70 Gitweb: http://git.kernel.org/tip/360cb4d15567a7eca07a5f3ade6de308bbfb4e70 Author: Andy Lutomirski <[email protected]> AuthorDate: Thu, 14 Jul 2016 13:22:50 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 15 Jul 2016 10:26:25 +0200
x86/mm/cpa: In populate_pgd(), don't set the PGD entry until it's populated This avoids pointless races in which another CPU or task might see a partially populated global PGD entry. These races should normally be harmless, but, if another CPU propagates the entry via vmalloc_fault() and then populate_pgd() fails (due to memory allocation failure, for example), this prevents a use-after-free of the PGD entry. Signed-off-by: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/bf99df27eac6835f687005364bd1fbd89130946c.1468527351.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/mm/pageattr.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 7514215..26aa487 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -1104,8 +1104,6 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr) pud = (pud_t *)get_zeroed_page(GFP_KERNEL | __GFP_NOTRACK); if (!pud) return -1; - - set_pgd(pgd_entry, __pgd(__pa(pud) | _KERNPG_TABLE)); } pgprot_val(pgprot) &= ~pgprot_val(cpa->mask_clr); @@ -1113,11 +1111,16 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr) ret = populate_pud(cpa, addr, pgd_entry, pgprot); if (ret < 0) { - unmap_pgd_range(cpa->pgd, addr, + if (pud) + free_page((unsigned long)pud); + unmap_pud_range(pgd_entry, addr, addr + (cpa->numpages << PAGE_SHIFT)); return ret; } + if (pud) + set_pgd(pgd_entry, __pgd(__pa(pud) | _KERNPG_TABLE)); + cpa->numpages = ret; return 0; }
