linux-kernel - [PATCH] rdma/siw: Fix a use after free in siw_alloc

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Message-Id: <20210425132001.3994-1-lyl2019@mail.ustc.edu.cn>
Date:   Sun, 25 Apr 2021 06:20:01 -0700
From:   Lv Yunlong <lyl2019@...l.ustc.edu.cn>
To:     bmt@...ich.ibm.com, dledford@...hat.com, jgg@...pe.ca
Cc:     linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lv Yunlong <lyl2019@...l.ustc.edu.cn>
Subject: [PATCH] rdma/siw: Fix a use after free in siw_alloc_mr

Our code analyzer reported a uaf.

In siw_alloc_mr, it calls siw_mr_add_mem(mr,..). In the implementation
of siw_mr_add_mem(), mem is assigned to mr->mem and then mem is freed
via kfree(mem) if xa_alloc_cyclic() failed. Here, mr->mem still point
to a freed object. After, the execution continue up to the err_out branch
of siw_alloc_mr, and the freed mr->mem is used in siw_mr_drop_mem(mr).

Fixes: 2251334dcac9e ("rdma/siw: application buffer management")
Signed-off-by: Lv Yunlong <lyl2019@...l.ustc.edu.cn>
---
 drivers/infiniband/sw/siw/siw_mem.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/infiniband/sw/siw/siw_mem.c b/drivers/infiniband/sw/siw/siw_mem.c
index 34a910cf0edb..3bde3b6fca05 100644
--- a/drivers/infiniband/sw/siw/siw_mem.c
+++ b/drivers/infiniband/sw/siw/siw_mem.c
@@ -114,6 +114,7 @@ int siw_mr_add_mem(struct siw_mr *mr, struct ib_pd *pd, void *mem_obj,
 	if (xa_alloc_cyclic(&sdev->mem_xa, &id, mem, limit, &next,
 	    GFP_KERNEL) < 0) {
 		kfree(mem);
+		mr->mem = NULL;
 		return -ENOMEM;
 	}
 	/* Set the STag index part */
-- 
2.25.1