[PATCH 1/1] RDMA/rxe: Fix null deref on srq->rq.queue after resize failure

[Zhu Yanjun <yanjun.zhu@linux.dev>]

A NULL pointer dereference can occur in rxe_srq_chk_attr() when
ibv_modify_srq() is invoked twice in succession under certain error
conditions. The first call may fail in rxe_queue_resize(), which leads
rxe_srq_from_attr() to set srq->rq.queue = NULL. The second call then
triggers a crash (null deref) when accessing
srq->rq.queue->buf->index_mask.

Call Trace:
<TASK>
rxe_modify_srq+0x170/0x480 [rdma_rxe]
? __pfx_rxe_modify_srq+0x10/0x10 [rdma_rxe]
? uverbs_try_lock_object+0x4f/0xa0 [ib_uverbs]
? rdma_lookup_get_uobject+0x1f0/0x380 [ib_uverbs]
ib_uverbs_modify_srq+0x204/0x290 [ib_uverbs]
? __pfx_ib_uverbs_modify_srq+0x10/0x10 [ib_uverbs]
? tryinc_node_nr_active+0xe6/0x150
? uverbs_fill_udata+0xed/0x4f0 [ib_uverbs]
ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x2c0/0x470 [ib_uverbs]
? __pfx_ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x10/0x10 [ib_uverbs]
? uverbs_fill_udata+0xed/0x4f0 [ib_uverbs]
ib_uverbs_run_method+0x55a/0x6e0 [ib_uverbs]
? __pfx_ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x10/0x10 [ib_uverbs]
ib_uverbs_cmd_verbs+0x54d/0x800 [ib_uverbs]
? __pfx_ib_uverbs_cmd_verbs+0x10/0x10 [ib_uverbs]
? __pfx___raw_spin_lock_irqsave+0x10/0x10
? __pfx_do_vfs_ioctl+0x10/0x10
? ioctl_has_perm.constprop.0.isra.0+0x2c7/0x4c0
? __pfx_ioctl_has_perm.constprop.0.isra.0+0x10/0x10
ib_uverbs_ioctl+0x13e/0x220 [ib_uverbs]
? __pfx_ib_uverbs_ioctl+0x10/0x10 [ib_uverbs]
__x64_sys_ioctl+0x138/0x1c0
do_syscall_64+0x82/0x250
? fdget_pos+0x58/0x4c0
? ksys_write+0xf3/0x1c0
? __pfx_ksys_write+0x10/0x10
? do_syscall_64+0xc8/0x250
? __pfx_vm_mmap_pgoff+0x10/0x10
? fget+0x173/0x230
? fput+0x2a/0x80
? ksys_mmap_pgoff+0x224/0x4c0
? do_syscall_64+0xc8/0x250
? do_user_addr_fault+0x37b/0xfe0
? clear_bhb_loop+0x50/0xa0
? clear_bhb_loop+0x50/0xa0
? clear_bhb_loop+0x50/0xa0
entry_SYSCALL_64_after_hwframe+0x76/0x7e

Root cause: 
   The queue is released when the first failure of rxe_cq_resize_queue.
Thus, when rxe_cq_resize_queue is called again, the above call trace
will occur.

Fix:
Aligning the error handling path in rxe_srq_from_attr() with
rxe_cq_resize_queue(), which also uses rxe_queue_resize(): do not
nullify the queue when resize fails.

Reported-by: Liu Yi <asatsuyu.liu@gmail.com>
Closes: https://paste.ubuntu.com/p/Zhj65q6gr9/
Fixes: 8700e3e7c485 ("Soft RoCE driver")
Tested-by: Liu Yi <asatsuyu.liu@gmail.com>
Signed-off-by: Zhu Yanjun <yanjun.zhu@linux.dev>
---
 drivers/infiniband/sw/rxe/rxe_srq.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_srq.c b/drivers/infiniband/sw/rxe/rxe_srq.c
index 3661cb627d28..2a234f26ac10 100644
--- a/drivers/infiniband/sw/rxe/rxe_srq.c
+++ b/drivers/infiniband/sw/rxe/rxe_srq.c
@@ -171,7 +171,7 @@ int rxe_srq_from_attr(struct rxe_dev *rxe, struct rxe_srq *srq,
 				       udata, mi, &srq->rq.producer_lock,
 				       &srq->rq.consumer_lock);
 		if (err)
-			goto err_free;
+			return err;
 
 		srq->rq.max_wr = attr->max_wr;
 	}
@@ -180,11 +180,6 @@ int rxe_srq_from_attr(struct rxe_dev *rxe, struct rxe_srq *srq,
 		srq->limit = attr->srq_limit;
 
 	return 0;
-
-err_free:
-	rxe_queue_cleanup(q);
-	srq->rq.queue = NULL;
-	return err;
 }
 
 void rxe_srq_cleanup(struct rxe_pool_elem *elem)
-- 
2.51.0