linux-kernel - Re: [PATCH v2] rdma/siw: Fix a use after free in siw_alloc

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Date:   Tue, 27 Apr 2021 15:31:46 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Lv Yunlong <lyl2019@...l.ustc.edu.cn>
Cc:     bmt@...ich.ibm.com, dledford@...hat.com,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rdma/siw: Fix a use after free in siw_alloc_mr

On Sun, Apr 25, 2021 at 06:16:47PM -0700, Lv Yunlong wrote:
> 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@...l.ustc.edu.cn>
> Reviewed-by: Bernard Metzler <bmt@...ich.ihm.com>
> ---
>  drivers/infiniband/sw/siw/siw_mem.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Applied to for-next, thanks

Jason