Messages in this thread Patch in this message | | | From | Jiang Biao <> | Subject | [PATCH v4 1/2] x86/pti: check the return value of pti_user_pagetable_walk_p4d | Date | Fri, 20 Jul 2018 08:06:31 +0800 |
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pti_user_pagetable_walk_p4d() may return NULL, we should check the return value to avoid NULL pointer dereference. And add warning for fail allocation where NULL returned.
Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn> --- arch/x86/mm/pti.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 4d418e7..8679c64 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -176,7 +176,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
if (pgd_none(*pgd)) { unsigned long new_p4d_page = __get_free_page(gfp); - if (!new_p4d_page) + if (WARN_ON_ONCE(!new_p4d_page)) return NULL;
set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page))); @@ -195,9 +195,13 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address) static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) { gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); - p4d_t *p4d = pti_user_pagetable_walk_p4d(address); + p4d_t *p4d; pud_t *pud;
+ p4d = pti_user_pagetable_walk_p4d(address); + if (!p4d) + return NULL; + BUILD_BUG_ON(p4d_large(*p4d) != 0); if (p4d_none(*p4d)) { unsigned long new_pud_page = __get_free_page(gfp); @@ -354,6 +358,9 @@ static void __init pti_clone_p4d(unsigned long addr) pgd_t *kernel_pgd;
user_p4d = pti_user_pagetable_walk_p4d(addr); + if (!user_p4d) + return; + kernel_pgd = pgd_offset_k(addr); kernel_p4d = p4d_offset(kernel_pgd, addr); *user_p4d = *kernel_p4d; -- 2.7.4
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