xen/gntdev: fix gntdev_mmap() error exit path

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>

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index f01d58c7a042ed747ce2c9227af0c5429a78546e..a3e7be96527d7e3dc1d1c207b5b3abc14578c60e 100644 (file)
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -1017,8 +1017,10 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
                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);