linux-kernel - Re: [PATCH v2] IB/hfi1: Fix possible null-pointer dereference in _extend_sdma_tx

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Message-ID: <20210806121023.GA3391878@nvidia.com>
Date:   Fri, 6 Aug 2021 09:10:23 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Tuo Li <islituo@...il.com>
Cc:     mike.marciniszyn@...nelisnetworks.com,
        dennis.dalessandro@...nelisnetworks.com, dledford@...hat.com,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        baijiaju1990@...il.com, TOTE Robot <oslab@...nghua.edu.cn>
Subject: Re: [PATCH v2] IB/hfi1: Fix possible null-pointer dereference in
 _extend_sdma_tx_descs()

On Fri, Aug 06, 2021 at 01:39:53AM -0700, Tuo Li wrote:
> kmalloc_array() is called to allocate memory for tx->descp. If it fails,
> the function __sdma_txclean() is called:
>   __sdma_txclean(dd, tx);
> 
> However, in the function __sdma_txclean(), tx-descp is dereferenced if
> tx->num_desc is not zero:
>   sdma_unmap_desc(dd, &tx->descp[0]);
> 
> To fix this possible null-pointer dereference, assign the return value of
> kmalloc_array() to a local variable descp, and then assign it to tx->descp
> if it is not NULL. Otherwise, go to enomem.
> 
> Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
> Signed-off-by: Tuo Li <islituo@...il.com>
> ---
> v2:
> * Assign the return value of kmalloc_array() to a local variable and then
> check it instead of assigning 0 to tx->num_desc when memory allocation
> fails.
>   Thank Mike Marciniszyn for helpful advice.
> ---
>  drivers/infiniband/hw/hfi1/sdma.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)

Fixes line?

Jason