Messages in this thread Patch in this message | | | From | Jiang Biao <> | Subject | [PATCH v4 2/2] x86/pti: check the return value of pti_user_pagetable_walk_pmd | Date | Fri, 20 Jul 2018 08:06:32 +0800 |
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Check the return value of pti_user_pagetable_walk_pmd() to avoid NULL pointer dereference. And add warning for fail allocation.
Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn> --- arch/x86/mm/pti.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 8679c64..5cd7b82 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -205,7 +205,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) BUILD_BUG_ON(p4d_large(*p4d) != 0); if (p4d_none(*p4d)) { unsigned long new_pud_page = __get_free_page(gfp); - if (!new_pud_page) + if (WARN_ON_ONCE(!new_pud_page)) return NULL;
set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page))); @@ -219,7 +219,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) } if (pud_none(*pud)) { unsigned long new_pmd_page = __get_free_page(gfp); - if (!new_pmd_page) + if (WARN_ON_ONCE(!new_pmd_page)) return NULL;
set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page))); @@ -241,9 +241,13 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address) { gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); - pmd_t *pmd = pti_user_pagetable_walk_pmd(address); + pmd_t *pmd; pte_t *pte;
+ pmd = pti_user_pagetable_walk_pmd(address); + if (!pmd) + return NULL; + /* We can't do anything sensible if we hit a large mapping. */ if (pmd_large(*pmd)) { WARN_ON(1); -- 2.7.4
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