[PATCH v2 2/2] RDMA/rxe: Reject prefetch of a non-ODP MR

[Norbert Szetei via B4 Relay]

From: Norbert Szetei <norbert@xxxxxxxxxxxx>

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

Ask lookup_mr() for IB_ACCESS_ON_DEMAND in both the synchronous and
the asynchronous prefetch arm. mr->access carries that flag only for
an MR registered as ODP, so the existing
(access & mr->access) != access test rejects a plain MR and the
prefetch fails with -EINVAL.

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 | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
index ab21b620e94c..c375d3efd999 100644
--- a/drivers/infiniband/sw/rxe/rxe_odp.c
+++ b/drivers/infiniband/sw/rxe/rxe_odp.c
@@ -469,7 +469,7 @@ static int rxe_ib_prefetch_sg_list(struct ib_pd *ibpd,
 		struct rxe_mr *mr;
 		struct ib_umem_odp *umem_odp;
 
-		mr = lookup_mr(pd, IB_ACCESS_LOCAL_WRITE,
+		mr = lookup_mr(pd, IB_ACCESS_LOCAL_WRITE | IB_ACCESS_ON_DEMAND,
 			       sg_list[i].lkey, RXE_LOOKUP_LOCAL);
 
 		if (!mr) {
@@ -535,7 +535,7 @@ static int rxe_ib_advise_mr_prefetch(struct ib_pd *ibpd,
 
 	for (i = 0; i < num_sge; ++i) {
 		/* Takes a reference, which will be released in the queued work */
-		mr = lookup_mr(pd, IB_ACCESS_LOCAL_WRITE,
+		mr = lookup_mr(pd, IB_ACCESS_LOCAL_WRITE | IB_ACCESS_ON_DEMAND,
 			       sg_list[i].lkey, RXE_LOOKUP_LOCAL);
 		if (!mr) {
 			mr = ERR_PTR(-EINVAL);

-- 
2.55.0