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    Subject[RFC PATCH v3 03/11] mseal: add can_modify_mm and can_modify_vma
    Date
    From: Jeff Xu <jeffxu@chromium.org>

    Two utilities to be used later.

    can_modify_mm:
    checks sealing flags for given memory range.

    can_modify_vma:
    checks sealing flags for given vma.

    Signed-off-by: Jeff Xu <jeffxu@chromium.org>
    ---
    include/linux/mm.h | 18 ++++++++++++++++++
    mm/mseal.c | 38 ++++++++++++++++++++++++++++++++++++++
    2 files changed, 56 insertions(+)

    diff --git a/include/linux/mm.h b/include/linux/mm.h
    index 3d1120570de5..2435acc1f44f 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -3339,6 +3339,12 @@ static inline unsigned long vma_seals(struct vm_area_struct *vma)
    return (vma->vm_seals & MM_SEAL_ALL);
    }

    +extern bool can_modify_mm(struct mm_struct *mm, unsigned long start,
    + unsigned long end, unsigned long checkSeals);
    +
    +extern bool can_modify_vma(struct vm_area_struct *vma,
    + unsigned long checkSeals);
    +
    #else
    static inline bool check_vma_seals_mergeable(unsigned long vm_seals1)
    {
    @@ -3349,6 +3355,18 @@ static inline unsigned long vma_seals(struct vm_area_struct *vma)
    {
    return 0;
    }
    +
    +static inline bool can_modify_mm(struct mm_struct *mm, unsigned long start,
    + unsigned long end, unsigned long checkSeals)
    +{
    + return true;
    +}
    +
    +static inline bool can_modify_vma(struct vm_area_struct *vma,
    + unsigned long checkSeals)
    +{
    + return true;
    +}
    #endif

    /* These take the mm semaphore themselves */
    diff --git a/mm/mseal.c b/mm/mseal.c
    index 13bbe9ef5883..d12aa628ebdc 100644
    --- a/mm/mseal.c
    +++ b/mm/mseal.c
    @@ -26,6 +26,44 @@ static bool can_do_mseal(unsigned long types, unsigned long flags)
    return true;
    }

    +/*
    + * check if a vma is sealed for modification.
    + * return true, if modification is allowed.
    + */
    +bool can_modify_vma(struct vm_area_struct *vma,
    + unsigned long checkSeals)
    +{
    + if (checkSeals & vma_seals(vma))
    + return false;
    +
    + return true;
    +}
    +
    +/*
    + * Check if the vmas of a memory range are allowed to be modified.
    + * the memory ranger can have a gap (unallocated memory).
    + * return true, if it is allowed.
    + */
    +bool can_modify_mm(struct mm_struct *mm, unsigned long start, unsigned long end,
    + unsigned long checkSeals)
    +{
    + struct vm_area_struct *vma;
    +
    + VMA_ITERATOR(vmi, mm, start);
    +
    + if (!checkSeals)
    + return true;
    +
    + /* going through each vma to check. */
    + for_each_vma_range(vmi, vma, end) {
    + if (!can_modify_vma(vma, checkSeals))
    + return false;
    + }
    +
    + /* Allow by default. */
    + return true;
    +}
    +
    /*
    * Check if a seal type can be added to VMA.
    */
    --
    2.43.0.472.g3155946c3a-goog
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