linux-kernel - Re: [PATCH] IB/mthca: Fix possible uninitialized-variable access in mthca_SYS

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Date:   Wed, 11 Aug 2021 15:49:00 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Tuo Li <islituo@...il.com>
Cc:     dledford@...hat.com, jgg@...pe.ca, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, baijiaju1990@...il.com,
        TOTE Robot <oslab@...nghua.edu.cn>
Subject: Re: [PATCH] IB/mthca: Fix possible uninitialized-variable access in
 mthca_SYS_EN()

On Wed, Aug 11, 2021 at 05:34:15AM -0700, Tuo Li wrote:
> The variable out is declared without initialization, and its address is 
> passed to mthca_cmd_imm():
>   ret = mthca_cmd_imm(dev, 0, &out, 0, 0, CMD_SYS_EN, CMD_TIME_CLASS_D);
> 
> In this function, mthca_cmd_wait() or mthca_cmd_poll() will be called with 
> the argument out_param, which is the address of the varialbe out. In these 
> two called functions, mthca_cmd_post() will be called with *out_param, 
> whose value comes from the uninitialized variable out.
>   err = mthca_cmd_post(dev, in_param, out_param ? *out_param : 0, ...)
> 
> In mthca_cmd_post(), mthca_cmd_post_dbell() or mthca_cmd_post_hcr() will 
> be called, in which the value from the uninitialized varialble out may be
> used:
>   __raw_writel((__force u32) cpu_to_be32(out_param >> 32), ptr + offs[3]);
> 
> To fix this possible uninitialized-variable access, initialized out to 0 
> at the begining of mthca_SYS_EN().
> 
> Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
> Signed-off-by: Tuo Li <islituo@...il.com>
> ---
>  drivers/infiniband/hw/mthca/mthca_cmd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Analysis is right, but I don't think that "out" value is important in
this flow.

Thanks

> 
> diff --git a/drivers/infiniband/hw/mthca/mthca_cmd.c b/drivers/infiniband/hw/mthca/mthca_cmd.c
> index bdf5ed38de22..86584982e496 100644
> --- a/drivers/infiniband/hw/mthca/mthca_cmd.c
> +++ b/drivers/infiniband/hw/mthca/mthca_cmd.c
> @@ -635,7 +635,7 @@ void mthca_free_mailbox(struct mthca_dev *dev, struct mthca_mailbox *mailbox)
>  
>  int mthca_SYS_EN(struct mthca_dev *dev)
>  {
> -	u64 out;
> +	u64 out = 0;
>  	int ret;
>  
>  	ret = mthca_cmd_imm(dev, 0, &out, 0, 0, CMD_SYS_EN, CMD_TIME_CLASS_D);
> -- 
> 2.25.1
>