From: Douglas Miller <doug.miller@xxxxxxxxxxxxxxxxxxxx>
Under certain conditions, such as MPI_Abort, the hfi1 cleanup
code may represent the last reference held on the task mm.
hfi1_mmu_rb_unregister() then drops the last reference and the mm is
freed before the final use in hfi1_release_user_pages(). A new task
may allocate the mm structure while it is still being used, resulting in
problems. One manifestation is corruption of the mmap_sem counter leading
to a hang in down_write(). Another is corruption of an mm struct that
is in use by another task.
Fixes: 3d2a9d642512 ("IB/hfi1: Ensure correct mm is used at all times")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Douglas Miller <doug.miller@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxxxxxxxxxxxxx>
---
drivers/infiniband/hw/hfi1/mmu_rb.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/infiniband/hw/hfi1/mmu_rb.c b/drivers/infiniband/hw/hfi1/mmu_rb.c
index 876cc78..7333646 100644
--- a/drivers/infiniband/hw/hfi1/mmu_rb.c
+++ b/drivers/infiniband/hw/hfi1/mmu_rb.c
@@ -80,6 +80,9 @@ void hfi1_mmu_rb_unregister(struct mmu_rb_handler *handler)
unsigned long flags;
struct list_head del_list;
+ /* Prevent freeing of mm until we are completely finished. */
+ mmgrab(handler->mn.mm);
+
/* Unregister first so we don't get any more notifications. */
mmu_notifier_unregister(&handler->mn, handler->mn.mm);
@@ -102,6 +105,9 @@ void hfi1_mmu_rb_unregister(struct mmu_rb_handler *handler)
do_remove(handler, &del_list);
+ /* Now the mm may be freed. */
+ mmdrop(handler->mn.mm);
+
kfree(handler);
}
