Commit b2b7d986 authored by Jiang Biao's avatar Jiang Biao Committed by Thomas Gleixner

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: default avatarJiang Biao <jiang.biao2@zte.com.cn>
Signed-off-by: default avatarThomas 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
parent 97193702
...@@ -176,7 +176,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address) ...@@ -176,7 +176,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
if (pgd_none(*pgd)) { if (pgd_none(*pgd)) {
unsigned long new_p4d_page = __get_free_page(gfp); unsigned long new_p4d_page = __get_free_page(gfp);
if (!new_p4d_page) if (WARN_ON_ONCE(!new_p4d_page))
return NULL; return NULL;
set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page))); 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) ...@@ -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) static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
{ {
gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
p4d_t *p4d = pti_user_pagetable_walk_p4d(address); p4d_t *p4d;
pud_t *pud; pud_t *pud;
p4d = pti_user_pagetable_walk_p4d(address);
if (!p4d)
return NULL;
BUILD_BUG_ON(p4d_large(*p4d) != 0); BUILD_BUG_ON(p4d_large(*p4d) != 0);
if (p4d_none(*p4d)) { if (p4d_none(*p4d)) {
unsigned long new_pud_page = __get_free_page(gfp); unsigned long new_pud_page = __get_free_page(gfp);
...@@ -359,6 +363,9 @@ static void __init pti_clone_p4d(unsigned long addr) ...@@ -359,6 +363,9 @@ static void __init pti_clone_p4d(unsigned long addr)
pgd_t *kernel_pgd; pgd_t *kernel_pgd;
user_p4d = pti_user_pagetable_walk_p4d(addr); user_p4d = pti_user_pagetable_walk_p4d(addr);
if (!user_p4d)
return;
kernel_pgd = pgd_offset_k(addr); kernel_pgd = pgd_offset_k(addr);
kernel_p4d = p4d_offset(kernel_pgd, addr); kernel_p4d = p4d_offset(kernel_pgd, addr);
*user_p4d = *kernel_p4d; *user_p4d = *kernel_p4d;
......
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