linux-kernel - Re: [PATCH] staging: tidspbridge: protect dmm

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Date:	Mon, 20 Dec 2010 12:30:27 -0600
From:	"Kanigeri, Hari" <h-kanigeri2@...com>
To:	Felipe Contreras <felipe.contreras@...ia.com>
Cc:	linux-main <linux-kernel@...r.kernel.org>,
	linux-omap <linux-omap@...r.kernel.org>,
	Greg KH <greg@...ah.com>,
	Omar Ramirez Luna <omar.ramirez@...com>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Fernando Guzman Lugo <fernando.lugo@...com>,
	Nishanth Menon <nm@...com>,
	Ameya Palande <ameya.palande@...ia.com>
Subject: Re: [PATCH] staging: tidspbridge: protect dmm_map properly

Felipe,

On Mon, Dec 20, 2010 at 11:12 AM, Felipe Contreras
<felipe.contreras@...ia.com> wrote:
> We need to protect not only the dmm_map list, but the individual
> map_obj's, otherwise, we might be building the scatter-gather list with
> garbage. So, use the existing proc_lock for that.
>
> I observed race conditions which caused kernel panics while running
> stress tests. This patch fixes those.
>
> Signed-off-by: Felipe Contreras <felipe.contreras@...ia.com>
> ---
>  drivers/staging/tidspbridge/rmgr/proc.c |   18 ++++++++++++++----
>  1 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/tidspbridge/rmgr/proc.c b/drivers/staging/tidspbridge/rmgr/proc.c
> index b47d7aa..21052e3 100644
> --- a/drivers/staging/tidspbridge/rmgr/proc.c
> +++ b/drivers/staging/tidspbridge/rmgr/proc.c
> @@ -781,12 +781,14 @@ int proc_begin_dma(void *hprocessor, void *pmpu_addr, u32 ul_size,
>                                                        (u32)pmpu_addr,
>                                                        ul_size, dir);
>
> +       mutex_lock(&proc_lock);

May be you should use mutex_lock_interruptable instead of  mutex_lock.

> +
>        /* find requested memory are in cached mapping information */
>        map_obj = find_containing_mapping(pr_ctxt, (u32) pmpu_addr, ul_size);
>        if (!map_obj) {
>                pr_err("%s: find_containing_mapping failed\n", __func__);
>                status = -EFAULT;
> -               goto err_out;
> +               goto no_map;
>        }
>
>        if (memory_give_ownership(map_obj, (u32) pmpu_addr, ul_size, dir)) {
> @@ -795,6 +797,8 @@ int proc_begin_dma(void *hprocessor, void *pmpu_addr, u32 ul_size,
>                status = -EFAULT;
>        }
>
> +no_map:
> +       mutex_unlock(&proc_lock);
>  err_out:
>
>        return status;
> @@ -819,12 +823,14 @@ int proc_end_dma(void *hprocessor, void *pmpu_addr, u32 ul_size,
>                                                        (u32)pmpu_addr,
>                                                        ul_size, dir);
>
> +       mutex_lock(&proc_lock);
> +
>        /* find requested memory are in cached mapping information */
>        map_obj = find_containing_mapping(pr_ctxt, (u32) pmpu_addr, ul_size);
>        if (!map_obj) {
>                pr_err("%s: find_containing_mapping failed\n", __func__);
>                status = -EFAULT;
> -               goto err_out;
> +               goto no_map;
>        }
>
>        if (memory_regain_ownership(map_obj, (u32) pmpu_addr, ul_size, dir)) {
> @@ -834,6 +840,8 @@ int proc_end_dma(void *hprocessor, void *pmpu_addr, u32 ul_size,
>                goto err_out;

Mutex is not released in this case as it is released only at no_map.


>        }
>
> +no_map:
> +       mutex_unlock(&proc_lock);
>  err_out:
>        return status;
>  }
> @@ -1726,9 +1734,8 @@ int proc_un_map(void *hprocessor, void *map_addr,
>                    (p_proc_object->hbridge_context, va_align, size_align);
>        }
>
> -       mutex_unlock(&proc_lock);
>        if (status)
> -               goto func_end;
> +               goto unmap_failed;
>
>        /*
>         * A successful unmap should be followed by removal of map_obj
> @@ -1737,6 +1744,9 @@ int proc_un_map(void *hprocessor, void *map_addr,
>         */
>        remove_mapping_information(pr_ctxt, (u32) map_addr, size_align);
>
> +unmap_failed:
> +       mutex_unlock(&proc_lock);
> +
>  func_end:
>        dev_dbg(bridge, "%s: hprocessor: 0x%p map_addr: 0x%p status: 0x%x\n",
>                __func__, hprocessor, map_addr, status);
> --
> 1.7.3.3
>
> --
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>



-- 
Thank you,
Best regards,
Hari Kanigeri
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