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Subject[PATCH v2] rdma/siw: Fix a use after free in siw_alloc_mr
Date
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).

My patch moves "mr->mem = mem" behind the if (xa_alloc_cyclic(..)<0) {}
section, to avoid the uaf.

Fixes: 2251334dcac9e ("rdma/siw: application buffer management")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
---
drivers/infiniband/sw/siw/siw_mem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/sw/siw/siw_mem.c b/drivers/infiniband/sw/siw/siw_mem.c
index 34a910cf0edb..96b38cfbb513 100644
--- a/drivers/infiniband/sw/siw/siw_mem.c
+++ b/drivers/infiniband/sw/siw/siw_mem.c
@@ -106,8 +106,6 @@ int siw_mr_add_mem(struct siw_mr *mr, struct ib_pd *pd, void *mem_obj,
mem->perms = rights & IWARP_ACCESS_MASK;
kref_init(&mem->ref);

- mr->mem = mem;
-
get_random_bytes(&next, 4);
next &= 0x00ffffff;

@@ -116,6 +114,8 @@ int siw_mr_add_mem(struct siw_mr *mr, struct ib_pd *pd, void *mem_obj,
kfree(mem);
return -ENOMEM;
}
+
+ mr->mem = mem;
/* Set the STag index part */
mem->stag = id << 8;
mr->base_mr.lkey = mr->base_mr.rkey = mem->stag;
--
2.25.1

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