Date:   Thu, 22 Sep 2022 11:00:23 +0800
From:   Zheng Hacker <hackerzheng666@...il.com>
To:     Zheng Wang <zyytlz.wz@....com>
Cc:     dimitri.sivanich@....com, arnd@...db.de,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        alex000young@...il.com, security@...nel.org
Subject: Re: [PATCH] misc: sgi-gru: fix use-after-free error in
 gru_set_context_option, gru_fault and gru_handle_user_call_os

Hi,

I've sent the patch with anothe account.
Could you please try this one?

Regards,
Zheng Wang

Zheng Wang <zyytlz.wz@....com> 于2022年9月19日周一 22:32写道：
>
> In grufile.c, gru_file_unlocked_ioctl function can be called by user.
>
> If the req is GRU_SET_CONTEXT_OPTION, it will call gru_set_context_option.
>
> In gru_set_context_option, as req can be controlled by user,
>
> We can reach gru_check_context_placement function call.
>
> In gru_check_context_placement function, if the error path was steped,
>
> say gru_check_chiplet_assignment return 0,
>
> Then it will fall into gru_unload_context function.
>
> And it will finnaly call kfree gts in gts_drop function.
>
> Then gru_unlock_gts will be called in gru_set_context_option function.
>
> This is a typical Use after free.
>
> The same problem exists in gru_handle_user_call_os and gru_fault.
>
> Fix it by introduce the return value to see if gts is in good case or not.
>
> Free the gts in caller when gru_check_chiplet_assignment check failed.
>
> Reported-by: Zheng Wang <hackerzheng666@...il.com> Zhuorao Yang <alex000young@...il.com>
>
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>
> ---
>  drivers/misc/sgi-gru/grufault.c  | 14 ++++++++++++--
>  drivers/misc/sgi-gru/grumain.c   | 17 +++++++++++++----
>  drivers/misc/sgi-gru/grutables.h |  2 +-
>  3 files changed, 26 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
> index d7ef61e602ed..2b5b049fbd38 100644
> --- a/drivers/misc/sgi-gru/grufault.c
> +++ b/drivers/misc/sgi-gru/grufault.c
> @@ -656,7 +656,9 @@ int gru_handle_user_call_os(unsigned long cb)
>         if (ucbnum >= gts->ts_cbr_au_count * GRU_CBR_AU_SIZE)
>                 goto exit;
>
> -       gru_check_context_placement(gts);
> +       ret = gru_check_context_placement(gts);
> +       if (ret)
> +               goto err;
>
>         /*
>          * CCH may contain stale data if ts_force_cch_reload is set.
> @@ -677,6 +679,10 @@ int gru_handle_user_call_os(unsigned long cb)
>  exit:
>         gru_unlock_gts(gts);
>         return ret;
> +err:
> +       gru_unlock_gts(gts);
> +       gru_unload_context(gts, 1);
> +       return -EINVAL;
>  }
>
>  /*
> @@ -874,7 +880,7 @@ int gru_set_context_option(unsigned long arg)
>                 } else {
>                         gts->ts_user_blade_id = req.val1;
>                         gts->ts_user_chiplet_id = req.val0;
> -                       gru_check_context_placement(gts);
> +                       ret = gru_check_context_placement(gts);
>                 }
>                 break;
>         case sco_gseg_owner:
> @@ -889,6 +895,10 @@ int gru_set_context_option(unsigned long arg)
>                 ret = -EINVAL;
>         }
>         gru_unlock_gts(gts);
> +       if (ret) {
> +               gru_unload_context(gts, 1);
> +               ret = -EINVAL;
> +       }
>
>         return ret;
>  }
> diff --git a/drivers/misc/sgi-gru/grumain.c b/drivers/misc/sgi-gru/grumain.c
> index 9afda47efbf2..79903cf7e706 100644
> --- a/drivers/misc/sgi-gru/grumain.c
> +++ b/drivers/misc/sgi-gru/grumain.c
> @@ -716,9 +716,10 @@ static int gru_check_chiplet_assignment(struct gru_state *gru,
>   * chiplet. Misassignment can occur if the process migrates to a different
>   * blade or if the user changes the selected blade/chiplet.
>   */
> -void gru_check_context_placement(struct gru_thread_state *gts)
> +int gru_check_context_placement(struct gru_thread_state *gts)
>  {
>         struct gru_state *gru;
> +       int ret = 0;
>
>         /*
>          * If the current task is the context owner, verify that the
> @@ -727,14 +728,16 @@ void gru_check_context_placement(struct gru_thread_state *gts)
>          */
>         gru = gts->ts_gru;
>         if (!gru || gts->ts_tgid_owner != current->tgid)
> -               return;
> +               return ret;
>
>         if (!gru_check_chiplet_assignment(gru, gts)) {
>                 STAT(check_context_unload);
> -               gru_unload_context(gts, 1);
> +               ret = -EINVAL;
>         } else if (gru_retarget_intr(gts)) {
>                 STAT(check_context_retarget_intr);
>         }
> +
> +       return ret;
>  }
>
>
> @@ -919,6 +922,7 @@ vm_fault_t gru_fault(struct vm_fault *vmf)
>         struct gru_thread_state *gts;
>         unsigned long paddr, vaddr;
>         unsigned long expires;
> +       int ret;
>
>         vaddr = vmf->address;
>         gru_dbg(grudev, "vma %p, vaddr 0x%lx (0x%lx)\n",
> @@ -934,7 +938,12 @@ vm_fault_t gru_fault(struct vm_fault *vmf)
>         mutex_lock(&gts->ts_ctxlock);
>         preempt_disable();
>
> -       gru_check_context_placement(gts);
> +       ret = gru_check_context_placement(gts);
> +       if (ret) {
> +               mutex_unlock(&gts->ts_ctxlock);
> +               gru_unload_context(gts, 1);
> +               return ret;
> +       }
>
>         if (!gts->ts_gru) {
>                 STAT(load_user_context);
> diff --git a/drivers/misc/sgi-gru/grutables.h b/drivers/misc/sgi-gru/grutables.h
> index 5efc869fe59a..f4a5a787685f 100644
> --- a/drivers/misc/sgi-gru/grutables.h
> +++ b/drivers/misc/sgi-gru/grutables.h
> @@ -632,7 +632,7 @@ extern int gru_user_flush_tlb(unsigned long arg);
>  extern int gru_user_unload_context(unsigned long arg);
>  extern int gru_get_exception_detail(unsigned long arg);
>  extern int gru_set_context_option(unsigned long address);
> -extern void gru_check_context_placement(struct gru_thread_state *gts);
> +extern int gru_check_context_placement(struct gru_thread_state *gts);
>  extern int gru_cpu_fault_map_id(void);
>  extern struct vm_area_struct *gru_find_vma(unsigned long vaddr);
>  extern void gru_flush_all_tlb(struct gru_state *gru);
> --
> 2.25.1
>

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