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| author | Hugh Dickins <hughd@google.com> | 2016-02-17 13:11:23 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-02-18 16:23:24 -0800 |
| commit | 457a98b0809fa6cde7aab8c314a59d99772b445e (patch) | |
| tree | 61fd434ac02707ba73f84db22a802215dd8469cf | |
| parent | 0918f1c309b86301605650c836ddd2021d311ae2 (diff) | |
| download | linux-457a98b0809fa6cde7aab8c314a59d99772b445e.tar.bz2 | |
mm, x86: fix pte_page() crash in gup_pte_range()
Commit 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") has
moved up the pte_page(pte) in x86's fast gup_pte_range(), for no
discernible reason: put it back where it belongs, after the pte_flags
check and the pfn_valid cross-check.
That may be the cause of the NULL pointer dereference in
gup_pte_range(), seen when vfio called vaddr_get_pfn() when starting a
qemu-kvm based VM.
Signed-off-by: Hugh Dickins <hughd@google.com>
Reported-by: Michael Long <Harn-Solo@gmx.de>
Tested-by: Michael Long <Harn-Solo@gmx.de>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | arch/x86/mm/gup.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index 6d5eb5900372..d8a798d8bf50 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -102,7 +102,6 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, return 0; } - page = pte_page(pte); if (pte_devmap(pte)) { pgmap = get_dev_pagemap(pte_pfn(pte), pgmap); if (unlikely(!pgmap)) { @@ -115,6 +114,7 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, return 0; } VM_BUG_ON(!pfn_valid(pte_pfn(pte))); + page = pte_page(pte); get_page(page); put_dev_pagemap(pgmap); SetPageReferenced(page); |