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    Subject[PATCH 4.16 028/272] IB/umem: Use the correct mm during ib_umem_release
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Lidong Chen <jemmy858585@gmail.com>

    commit 8e907ed4882714fd13cfe670681fc6cb5284c780 upstream.

    User-space may invoke ibv_reg_mr and ibv_dereg_mr in different threads.

    If ibv_dereg_mr is called after the thread which invoked ibv_reg_mr has
    exited, get_pid_task will return NULL and ib_umem_release will not
    decrease mm->pinned_vm.

    Instead of using threads to locate the mm, use the overall tgid from the
    ib_ucontext struct instead. This matches the behavior of ODP and
    disassociate in handling the mm of the process that called ibv_reg_mr.

    Cc: <stable@vger.kernel.org>
    Fixes: 87773dd56d54 ("IB: ib_umem_release() should decrement mm->pinned_vm from ib_umem_get")
    Signed-off-by: Lidong Chen <lidongchen@tencent.com>
    Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/infiniband/core/umem.c | 7 +------
    include/rdma/ib_umem.h | 1 -
    2 files changed, 1 insertion(+), 7 deletions(-)

    --- a/drivers/infiniband/core/umem.c
    +++ b/drivers/infiniband/core/umem.c
    @@ -119,7 +119,6 @@ struct ib_umem *ib_umem_get(struct ib_uc
    umem->length = size;
    umem->address = addr;
    umem->page_shift = PAGE_SHIFT;
    - umem->pid = get_task_pid(current, PIDTYPE_PID);
    /*
    * We ask for writable memory if any of the following
    * access flags are set. "Local write" and "remote write"
    @@ -132,7 +131,6 @@ struct ib_umem *ib_umem_get(struct ib_uc
    IB_ACCESS_REMOTE_ATOMIC | IB_ACCESS_MW_BIND));

    if (access & IB_ACCESS_ON_DEMAND) {
    - put_pid(umem->pid);
    ret = ib_umem_odp_get(context, umem, access);
    if (ret) {
    kfree(umem);
    @@ -148,7 +146,6 @@ struct ib_umem *ib_umem_get(struct ib_uc

    page_list = (struct page **) __get_free_page(GFP_KERNEL);
    if (!page_list) {
    - put_pid(umem->pid);
    kfree(umem);
    return ERR_PTR(-ENOMEM);
    }
    @@ -231,7 +228,6 @@ out:
    if (ret < 0) {
    if (need_release)
    __ib_umem_release(context->device, umem, 0);
    - put_pid(umem->pid);
    kfree(umem);
    } else
    current->mm->pinned_vm = locked;
    @@ -274,8 +270,7 @@ void ib_umem_release(struct ib_umem *ume

    __ib_umem_release(umem->context->device, umem, 1);

    - task = get_pid_task(umem->pid, PIDTYPE_PID);
    - put_pid(umem->pid);
    + task = get_pid_task(umem->context->tgid, PIDTYPE_PID);
    if (!task)
    goto out;
    mm = get_task_mm(task);
    --- a/include/rdma/ib_umem.h
    +++ b/include/rdma/ib_umem.h
    @@ -48,7 +48,6 @@ struct ib_umem {
    int writable;
    int hugetlb;
    struct work_struct work;
    - struct pid *pid;
    struct mm_struct *mm;
    unsigned long diff;
    struct ib_umem_odp *odp_data;

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