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authorAndy Lutomirski <luto@kernel.org>2016-07-14 13:22:50 -0700
committerIngo Molnar <mingo@kernel.org>2016-07-15 10:26:25 +0200
commit360cb4d15567a7eca07a5f3ade6de308bbfb4e70 (patch)
treecc75b47581140c5183b78fdb0a66144907d83073 /arch
parentaf2cf278ef4f9289f88504c3e03cb12f76027575 (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.c9
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;
}