[PATCH] RDMA/rxe: Reject prefetch of a non-ODP MR

[Norbert Szetei]

rxe_ib_advise_mr_prefetch() and rxe_ib_prefetch_sg_list() look up the MR
by lkey and hand it to rxe_odp_do_pagefault_and_lock() without checking
that it is an ODP MR. That path runs to_ib_umem_odp() on mr->umem, and
for a non-ODP MR mr->umem is a plain struct ib_umem from ib_umem_get(),
so the container_of() in to_ib_umem_odp() lands past the end of the
object and ib_umem_odp_map_dma_and_lock() reads its ib_umem_odp fields
out of bounds.

lookup_mr() validates the lkey, PD, access and state but not the MR
type, and IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH is accepted for any MR.

  BUG: KASAN: slab-out-of-bounds in ib_umem_odp_map_dma_and_lock+0x884/0x8a0
  Read of size 8 at addr ffff88810a3ebcf0 by task advi/921
   ib_umem_odp_map_dma_and_lock+0x884/0x8a0
   rxe_ib_advise_mr+0x543/0xad0
   ib_uverbs_handler_UVERBS_METHOD_ADVISE_MR+0x446/0x530
   ib_uverbs_cmd_verbs+0x2b3c/0x3b20
   ib_uverbs_ioctl+0x1e3/0x310
  Allocated by task 921:
   __ib_umem_get_va+0x13e/0xae0
   rxe_mr_init_user+0x2ae/0xb00
   rxe_reg_user_mr+0x337/0x510
  The buggy address belongs to the object at ffff88810a3ebc80
   which belongs to the cache kmalloc-96 of size 96

Reject a non-ODP MR after lookup_mr() in both the synchronous and
asynchronous prefetch arms.

Fixes: 3576b0df1588 ("RDMA/rxe: Implement synchronous prefetch for ODP MRs")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Norbert Szetei <norbert@xxxxxxxxxxxx>
---
 drivers/infiniband/sw/rxe/rxe_odp.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
index e870efa7a0a3..5c9dde3501a0 100644
--- a/drivers/infiniband/sw/rxe/rxe_odp.c
+++ b/drivers/infiniband/sw/rxe/rxe_odp.c
@@ -472,6 +472,11 @@ static int rxe_ib_prefetch_sg_list(struct ib_pd *ibpd,
 			return -EINVAL;
 		}
 
+		if (unlikely(!is_odp_mr(mr))) {
+			rxe_put(mr);
+			return -EOPNOTSUPP;
+		}
+
 		if (advice == IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_WRITE &&
 		    !mr->umem->writable) {
 			rxe_dbg_mr(mr, "missing write permission\n");
@@ -536,6 +541,12 @@ static int rxe_ib_advise_mr_prefetch(struct ib_pd *ibpd,
 			goto err;
 		}
 
+		if (unlikely(!is_odp_mr(mr))) {
+			rxe_put(mr);
+			mr = ERR_PTR(-EOPNOTSUPP);
+			goto err;
+		}
+
 		work->frags[i].io_virt = sg_list[i].addr;
 		work->frags[i].length = sg_list[i].length;
 		work->frags[i].mr = mr;
-- 
2.55.0