[PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Wang]

Gts may be freed in gru_check_chiplet_assignment.
The caller still use it after that, UAF happens.

Fix it by introducing a return value to see if it's in error path or not. 
Free the gts in caller if gru_check_chiplet_assignment check failed.

Reported-by: Zheng Wang <hackerzheng666@gmail.com>

Signed-off-by: Zheng Wang <zyytlz.wz@163.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

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Greg KH]

On Mon, Sep 26, 2022 at 12:36:18PM +0800, Zheng Wang wrote:
> Gts may be freed in gru_check_chiplet_assignment.
> The caller still use it after that, UAF happens.
> 
> Fix it by introducing a return value to see if it's in error path or not. 
> Free the gts in caller if gru_check_chiplet_assignment check failed.
> 
> Reported-by: Zheng Wang <hackerzheng666@gmail.com>
> 
> Signed-off-by: Zheng Wang <zyytlz.wz@163.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
> 
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/SubmittingPatches for what needs to be done
  here to properly describe this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

Hi Greg,

I've resent the patch. Could you please review it and apply if there
is no more problem?

Thanks,
Zheng Wang

Greg KH <gregkh@linuxfoundation.org> 于2022年9月26日周一 16:36写道：
>
> On Mon, Sep 26, 2022 at 12:36:18PM +0800, Zheng Wang wrote:
> > Gts may be freed in gru_check_chiplet_assignment.
> > The caller still use it after that, UAF happens.
> >
> > Fix it by introducing a return value to see if it's in error path or not.
> > Free the gts in caller if gru_check_chiplet_assignment check failed.
> >
> > Reported-by: Zheng Wang <hackerzheng666@gmail.com>
> >
> > Signed-off-by: Zheng Wang <zyytlz.wz@163.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
> >
> >
>
> Hi,
>
> This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
> a patch that has triggered this response.  He used to manually respond
> to these common problems, but in order to save his sanity (he kept
> writing the same thing over and over, yet to different people), I was
> created.  Hopefully you will not take offence and will fix the problem
> in your patch and resubmit it so that it can be accepted into the Linux
> kernel tree.
>
> You are receiving this message because of the following common error(s)
> as indicated below:
>
> - This looks like a new version of a previously submitted patch, but you
>   did not list below the --- line any changes from the previous version.
>   Please read the section entitled "The canonical patch format" in the
>   kernel file, Documentation/SubmittingPatches for what needs to be done
>   here to properly describe this.
>
> If you wish to discuss this problem further, or you have questions about
> how to resolve this issue, please feel free to respond to this email and
> Greg will reply once he has dug out from the pending patches received
> from other developers.
>
> thanks,
>
> greg k-h's patch email bot

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Greg KH]

Please do not top-post.

On Tue, Sep 27, 2022 at 10:12:58PM +0800, Zheng Hacker wrote:
> Hi Greg,
> 
> I've resent the patch. Could you please review it and apply if there
> is no more problem?

I do not see any new submission, please provide the lore.kernel.org link
of it.

thanks,

greg k-h

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

Greg KH <gregkh@linuxfoundation.org> 于2022年9月28日周三 00:36写道：
>
> Please do not top-post.
>
Got it :)
> I do not see any new submission, please provide the lore.kernel.org link
> of it.
>
Here is the link of new
patch(https://lore.kernel.org/all/20220928025957.1050698-1-zyytlz.wz@163.com/T/#u),
I added the Fixes line to tell which commit introduced the bug.

Thanks,
Zheng Wang

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

Here is the link of new
patch(https://lore.kernel.org/all/20220928025957.1050698-1-zyytlz.wz@163.com/T/#u),
I added the Fixes line to tell which commit introduced the bug.

Thanks,
Zheng Wang

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Greg KH]

On Sun, Oct 02, 2022 at 07:25:32PM +0800, Zheng Hacker wrote:
> Here is the link of new
> patch(https://lore.kernel.org/all/20220928025957.1050698-1-zyytlz.wz@163.com/T/#u),
> I added the Fixes line to tell which commit introduced the bug.

Did you not see my bot's response to your submission?  It is in the link
you provided above, why ignore that?

greg k-h

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

Hi Greg,

Sorry for my mistak. I thought reopening another theme is fine. I'll
read it carefully and send th pach again.

Regards,
Zheng Wang

[PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Wang]

Gts may be freed in gru_check_chiplet_assignment.
The caller still use it after that, UAF happens.

Fix it by introducing a return value to see if it's in error path or not. 
Free the gts in caller if gru_check_chiplet_assignment check failed.

Reported-by: Zheng Wang <hackerzheng666@gmail.com>
             Zhuorao Yang <alex000young@gmail.com>

Signed-off-by: Zheng Wang <zyytlz.wz@163.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

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

Hi Greg,

Very happy to receive your email. I was outgoing in the weekend and
sorry for my late reply. I'll fix the patch and resend it to you.

Best regards,
Zheng Wang

Greg KH <gregkh@linuxfoundation.org> 于2022年9月24日周六 20:54写道：
>
> On Mon, Sep 19, 2022 at 10:32:05PM +0800, Zheng Wang wrote:
> > 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.
>
> Your text formatting is a bit odd, don't you think?
>
> >
> > Reported-by: Zheng Wang <hackerzheng666@gmail.com> Zhuorao Yang <alex000young@gmail.com>
>
> Why twice?
>
> Should be two different reported-by lines, right?
>
> Otherwise looks good, can you fix that up and resend?
>
> thanks,
>
> greg k-h

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Greg KH]

On Mon, Sep 19, 2022 at 10:32:05PM +0800, Zheng Wang wrote:
> 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.

Your text formatting is a bit odd, don't you think?

> 
> Reported-by: Zheng Wang <hackerzheng666@gmail.com> Zhuorao Yang <alex000young@gmail.com>

Why twice?

Should be two different reported-by lines, right?

Otherwise looks good, can you fix that up and resend?

thanks,

greg k-h

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

Hi,

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

Regards,
Zheng Wang

Zheng Wang <zyytlz.wz@163.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@gmail.com> Zhuorao Yang <alex000young@gmail.com>
>
> Signed-off-by: Zheng Wang <zyytlz.wz@163.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
>

[PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Wang]

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@gmail.com> Zhuorao Yang <alex000young@gmail.com>

Signed-off-by: Zheng Wang <zyytlz.wz@163.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

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

From 7cdd08c87a3252ffa081997146dd9c3adcb37f1c Mon Sep 17 00:00:00 2001
From: xmzyshypnc <1002992920@qq.com>
Date: Fri, 16 Sep 2022 17:54:07 +0800
Subject: [PATCH] misc: sgi-gru: fix use-after-free error in
 gru_set_context_option, gru_fault and gru_handle_user_call_os

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.

Signed-off-by: xmzyshypnc <1002992920@qq.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

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

From 7cdd08c87a3252ffa081997146dd9c3adcb37f1c Mon Sep 17 00:00:00 2001
From: xmzyshypnc <1002992920@qq.com>
Date: Fri, 16 Sep 2022 17:54:07 +0800
Subject: [PATCH] misc: sgi-gru: fix use-after-free error in
 gru_set_context_option, gru_fault and gru_handle_user_call_os

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.

Signed-off-by: xmzyshypnc <1002992920@qq.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

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

Hi greg,

I've received your advice and rewrite the patch.

Greg KH <gregkh@linuxfoundation.org> 于2022年9月16日周五 16:15写道：
>
> On Fri, Sep 16, 2022 at 03:39:57PM +0800, xmzyshypnc wrote:
> > in drivers/misc/sgi-gru/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.
>
> Please properly wrap your changelog text at 72 columns like your editor
> asked you to when you wrote the changelog text.
>
> >
> > In gru_set_context_option, as req can be controlled by user (copy_from_user(&req, (void __user *)arg, sizeof(req))), we can get into sco_blade_chiplet case and 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,which will call gru_free_gru_context->gts_drop. As gts->ts_refcnt was set to 1 in gru_alloc_gts. It will finnaly call kfree(gts) in gts_drop function.
> >
> > Then gru_unlock_gts will be called in gru_set_context_option function. which is a typical Use after free.
> >
> > The same problem exists in gru_handle_user_call_os function and gru_fault function.
> >
> > 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.
> >
> > Signed-off-by: xmzyshypnc <1002992920@qq.com>
> > ---
> >  drivers/misc/sgi-gru/grufault.c  | 14 ++++++++++++--
> >  drivers/misc/sgi-gru/grumain.c   | 19 +++++++++++++++----
> >  drivers/misc/sgi-gru/grutables.h |  2 +-
> >  3 files changed, 28 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
> > index d7ef61e602ed..08e837a45ad7 100644
> > --- a/drivers/misc/sgi-gru/grufault.c
> > +++ b/drivers/misc/sgi-gru/grufault.c
> > @@ -656,7 +656,13 @@ 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) {
>
> No blank line needed.

Got it.

>
> > +             gru_unlock_gts(gts);
> > +             gru_unload_context(gts, 1);
> > +             return -EINVAL;
>
> Jump to an error block at the end of the function instead?
>
> > +     }
> >
> >       /*
> >        * CCH may contain stale data if ts_force_cch_reload is set.
> > @@ -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..e1ecf86df3c1 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;
>
> Why is this succeeding if there was an error?
>

The logic code here is when gts->ts_gru is null, it try again. It
won't free the gts so I think it can still be called after this
branch.

> >
> >       if (!gru_check_chiplet_assignment(gru, gts)) {
> >               STAT(check_context_unload);
> > -             gru_unload_context(gts, 1);
> > +             ret = 1;
>
> 1 is not a valid error value;
>
>
> >       } 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 VM_FAULT_NOPAGE;
>
> Why not return ret?
>

Got it.

> > +     }
> >
> >       if (!gts->ts_gru) {
> >               STAT(load_user_context);
> > @@ -958,6 +967,8 @@ vm_fault_t gru_fault(struct vm_fault *vmf)
> >       preempt_enable();
> >       mutex_unlock(&gts->ts_ctxlock);
> >
> > +
> > +
>
> Why the blank lines added?
>

Removed.

Best regards,

Zheng Wang

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Greg KH]

On Fri, Sep 16, 2022 at 05:59:14PM +0800, xmzyshypnc wrote:
> 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.
> 
> Signed-off-by: xmzyshypnc <1002992920@qq.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
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- You did not specify a description of why the patch is needed, or
  possibly, any description at all, in the email body.  Please read the
  section entitled "The canonical patch format" in the kernel file,
  Documentation/SubmittingPatches for what is needed in order to
  properly describe the change.

- You did not write a descriptive Subject: for the patch, allowing Greg,
  and everyone else, to know what this patch is all about.  Please read
  the section entitled "The canonical patch format" in the kernel file,
  Documentation/SubmittingPatches for what a proper Subject: line should
  look like.

- It looks like you did not use your "real" name for the patch on either
  the Signed-off-by: line, or the From: line (both of which have to
  match).  Please read the kernel file, Documentation/SubmittingPatches
  for how to do this correctly.

- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/SubmittingPatches for what needs to be done
  here to properly describe this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Greg KH]

On Fri, Sep 16, 2022 at 03:39:57PM +0800, xmzyshypnc wrote:
> in drivers/misc/sgi-gru/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.

Please properly wrap your changelog text at 72 columns like your editor
asked you to when you wrote the changelog text.

> 
> In gru_set_context_option, as req can be controlled by user (copy_from_user(&req, (void __user *)arg, sizeof(req))), we can get into sco_blade_chiplet case and 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,which will call gru_free_gru_context->gts_drop. As gts->ts_refcnt was set to 1 in gru_alloc_gts. It will finnaly call kfree(gts) in gts_drop function.
> 
> Then gru_unlock_gts will be called in gru_set_context_option function. which is a typical Use after free.
> 
> The same problem exists in gru_handle_user_call_os function and gru_fault function.
> 
> 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.
> 
> Signed-off-by: xmzyshypnc <1002992920@qq.com>
> ---
>  drivers/misc/sgi-gru/grufault.c  | 14 ++++++++++++--
>  drivers/misc/sgi-gru/grumain.c   | 19 +++++++++++++++----
>  drivers/misc/sgi-gru/grutables.h |  2 +-
>  3 files changed, 28 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
> index d7ef61e602ed..08e837a45ad7 100644
> --- a/drivers/misc/sgi-gru/grufault.c
> +++ b/drivers/misc/sgi-gru/grufault.c
> @@ -656,7 +656,13 @@ 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) {

No blank line needed.

> +		gru_unlock_gts(gts);
> +		gru_unload_context(gts, 1);
> +		return -EINVAL;

Jump to an error block at the end of the function instead?

> +	}
>  
>  	/*
>  	 * CCH may contain stale data if ts_force_cch_reload is set.
> @@ -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..e1ecf86df3c1 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;

Why is this succeeding if there was an error?

>  
>  	if (!gru_check_chiplet_assignment(gru, gts)) {
>  		STAT(check_context_unload);
> -		gru_unload_context(gts, 1);
> +		ret = 1;

1 is not a valid error value;


>  	} 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 VM_FAULT_NOPAGE;

Why not return ret?

> +	}
>  
>  	if (!gts->ts_gru) {
>  		STAT(load_user_context);
> @@ -958,6 +967,8 @@ vm_fault_t gru_fault(struct vm_fault *vmf)
>  	preempt_enable();
>  	mutex_unlock(&gts->ts_ctxlock);
>  
> +
> +

Why the blank lines added?

thanks,

greg k-h