From: Douglas Miller Date: Fri, 8 Apr 2022 13:35:23 +0000 (-0400) Subject: RDMA/hfi1: Fix use-after-free bug for mm struct X-Git-Tag: microblaze-v5.20~475^2 X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=2bbac98d0930e8161b1957dc0ec99de39ade1b3c;p=linux-2.6-microblaze.git RDMA/hfi1: Fix use-after-free bug for mm struct 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") Link: https://lore.kernel.org/r/20220408133523.122165.72975.stgit@awfm-01.cornelisnetworks.com Cc: Signed-off-by: Douglas Miller Signed-off-by: Dennis Dalessandro Signed-off-by: Jason Gunthorpe --- diff --git a/drivers/infiniband/hw/hfi1/mmu_rb.c b/drivers/infiniband/hw/hfi1/mmu_rb.c index 876cc78a22cc..7333646021bb 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); }