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x86/pti: Check the return value of pti_user_pagetable_walk_p4d()
pti_user_pagetable_walk_p4d() can return NULL, so the return value should be checked to prevent a NULL pointer dereference. Add the check and a warning when the P4D allocation fails. Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: dave.hansen@linux.intel.com Cc: luto@kernel.org Cc: hpa@zytor.com Cc: albcamus@gmail.com Cc: zhong.weidong@zte.com.cn Link: https://lkml.kernel.org/r/1532045192-49622-1-git-send-email-jiang.biao2@zte.com.cn
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1 changed files with 9 additions and 2 deletions
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@ -176,7 +176,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
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if (pgd_none(*pgd)) {
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unsigned long new_p4d_page = __get_free_page(gfp);
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if (!new_p4d_page)
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if (WARN_ON_ONCE(!new_p4d_page))
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return NULL;
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set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
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@ -195,9 +195,13 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
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static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
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{
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gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
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p4d_t *p4d = pti_user_pagetable_walk_p4d(address);
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p4d_t *p4d;
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pud_t *pud;
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p4d = pti_user_pagetable_walk_p4d(address);
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if (!p4d)
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return NULL;
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BUILD_BUG_ON(p4d_large(*p4d) != 0);
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if (p4d_none(*p4d)) {
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unsigned long new_pud_page = __get_free_page(gfp);
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@ -359,6 +363,9 @@ static void __init pti_clone_p4d(unsigned long addr)
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pgd_t *kernel_pgd;
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user_p4d = pti_user_pagetable_walk_p4d(addr);
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if (!user_p4d)
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return;
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kernel_pgd = pgd_offset_k(addr);
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kernel_p4d = p4d_offset(kernel_pgd, addr);
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*user_p4d = *kernel_p4d;
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