diff options
| author | Andy Lutomirski <luto@kernel.org> | 2016-07-14 13:22:50 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-07-15 10:26:25 +0200 |
| commit | 360cb4d15567a7eca07a5f3ade6de308bbfb4e70 (patch) | |
| tree | cc75b47581140c5183b78fdb0a66144907d83073 /arch | |
| parent | af2cf278ef4f9289f88504c3e03cb12f76027575 (diff) | |
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 <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/bf99df27eac6835f687005364bd1fbd89130946c.1468527351.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/mm/pageattr.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 75142159b0a5..26aa487ae4ef 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; } |