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    Subject[PATCH 5.11 297/329] xen/gntdev: fix gntdev_mmap() error exit path
    Date
    From: Juergen Gross <jgross@suse.com>

    commit 970655aa9b42461f8394e4457307005bdeee14d9 upstream.

    Commit d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert")
    introduced an error in gntdev_mmap(): in case the call of
    mmu_interval_notifier_insert_locked() fails the exit path should not
    call mmu_interval_notifier_remove(), as this might result in NULL
    dereferences.

    One reason for failure is e.g. a signal pending for the running
    process.

    Fixes: d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert")
    Cc: stable@vger.kernel.org
    Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
    Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
    Signed-off-by: Juergen Gross <jgross@suse.com>
    Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
    Link: https://lore.kernel.org/r/20210423054038.26696-1-jgross@suse.com
    Signed-off-by: Juergen Gross <jgross@suse.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/xen/gntdev.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/drivers/xen/gntdev.c
    +++ b/drivers/xen/gntdev.c
    @@ -1005,8 +1005,10 @@ static int gntdev_mmap(struct file *flip
    err = mmu_interval_notifier_insert_locked(
    &map->notifier, vma->vm_mm, vma->vm_start,
    vma->vm_end - vma->vm_start, &gntdev_mmu_ops);
    - if (err)
    + if (err) {
    + map->vma = NULL;
    goto out_unlock_put;
    + }
    }
    mutex_unlock(&priv->lock);


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