lkml.org 
[lkml]   [2018]   [Sep]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH AUTOSEL 4.14 65/67] x86/pti: Check the return value of pti_user_pagetable_walk_p4d()
    Date
    From: Jiang Biao <jiang.biao2@zte.com.cn>

    [ Upstream commit b2b7d986a89b6c94b1331a909de1217214fb08c1 ]

    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
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    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 d6f11accd37a..63afd15b32a5 100644
    --- a/arch/x86/mm/pti.c
    +++ b/arch/x86/mm/pti.c
    @@ -162,7 +162,7 @@ static __init 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)));
    @@ -181,9 +181,13 @@ static __init p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
    static __init 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);
    @@ -319,6 +323,9 @@ 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;
    --
    2.17.1
    \
     
     \ /
      Last update: 2018-09-07 02:41    [W:14.148 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site