xen/gntdev: fix gntdev_mmap() error exit path

BugLink: https://bugs.launchpad.net/bugs/1931292
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 5447c5156b2e62ea50f8190609a85db42904b4ed..b9651f797676c47b036c6f7c173ee9130383bcc4 100644 (file)
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -1005,8 +1005,10 @@ 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);