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authorJason Gunthorpe <jgg@mellanox.com>2020-02-27 13:41:18 +0200
committerJason Gunthorpe <jgg@mellanox.com>2020-03-04 13:56:07 -0400
commita4e63bce1414df7ab6eb82ca9feb8494ce13e554 (patch)
tree29db5367405979d5c353761fec56209161a1001a
parentRDMA/core: Fix protection fault in ib_mr_pool_destroy (diff)
downloadlinux-dev-a4e63bce1414df7ab6eb82ca9feb8494ce13e554.tar.xz
linux-dev-a4e63bce1414df7ab6eb82ca9feb8494ce13e554.zip
RDMA/odp: Ensure the mm is still alive before creating an implicit child
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>
-rw-r--r--drivers/infiniband/core/umem_odp.c24
1 files changed, 19 insertions, 5 deletions
diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index b8c657b28380..cd656ad4953b 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -181,14 +181,28 @@ ib_umem_odp_alloc_child(struct ib_umem_odp *root, unsigned long addr,
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);