| From a4e63bce1414df7ab6eb82ca9feb8494ce13e554 Mon Sep 17 00:00:00 2001 |
| From: Jason Gunthorpe <jgg@ziepe.ca> |
| Date: Thu, 27 Feb 2020 13:41:18 +0200 |
| Subject: RDMA/odp: Ensure the mm is still alive before creating an implicit child |
| |
| From: Jason Gunthorpe <jgg@mellanox.com> |
| |
| commit a4e63bce1414df7ab6eb82ca9feb8494ce13e554 upstream. |
| |
| Registration of a mmu_notifier requires the caller to hold a mmget() on |
| the mm as registration is not permitted to race with exit_mmap(). There is |
| a BUG_ON inside the mmu_notifier to guard against this. |
| |
| Normally creating a umem is done against current which implicitly holds |
| the mmget(), however an implicit ODP child is created from a pagefault |
| work queue and is not guaranteed to have a mmget(). |
| |
| Call mmget() around this registration and abort faulting if the MM has |
| gone to exit_mmap(). |
| |
| Before the patch below the notifier was registered when the implicit ODP |
| parent was created, so there was no chance to register a notifier outside |
| of current. |
| |
| Fixes: c571feca2dc9 ("RDMA/odp: use mmu_notifier_get/put for 'struct ib_ucontext_per_mm'") |
| Link: https://lore.kernel.org/r/20200227114118.94736-1-leon@kernel.org |
| Signed-off-by: Leon Romanovsky <leonro@mellanox.com> |
| Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/infiniband/core/umem_odp.c | 24 +++++++++++++++++++----- |
| 1 file changed, 19 insertions(+), 5 deletions(-) |
| |
| --- a/drivers/infiniband/core/umem_odp.c |
| +++ b/drivers/infiniband/core/umem_odp.c |
| @@ -187,14 +187,28 @@ ib_umem_odp_alloc_child(struct ib_umem_o |
| odp_data->page_shift = PAGE_SHIFT; |
| odp_data->notifier.ops = ops; |
| |
| + /* |
| + * A mmget must be held when registering a notifier, the owming_mm only |
| + * has a mm_grab at this point. |
| + */ |
| + if (!mmget_not_zero(umem->owning_mm)) { |
| + ret = -EFAULT; |
| + goto out_free; |
| + } |
| + |
| odp_data->tgid = get_pid(root->tgid); |
| ret = ib_init_umem_odp(odp_data, ops); |
| - if (ret) { |
| - put_pid(odp_data->tgid); |
| - kfree(odp_data); |
| - return ERR_PTR(ret); |
| - } |
| + if (ret) |
| + goto out_tgid; |
| + mmput(umem->owning_mm); |
| return odp_data; |
| + |
| +out_tgid: |
| + put_pid(odp_data->tgid); |
| + mmput(umem->owning_mm); |
| +out_free: |
| + kfree(odp_data); |
| + return ERR_PTR(ret); |
| } |
| EXPORT_SYMBOL(ib_umem_odp_alloc_child); |
| |