[PATCH v4] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[PATCH v4] 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.

Fixes: 55484c45dbec ("gru: allow users to specify gru chiplet 2")
Reported-by: Zheng Wang <hackerzheng666@gmail.com>
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
---
v4:
- use VM_FAULT_NOPAGE as failure code in gru_fault and -EINVAL in other functions suggested by Yejian

v3:
- add preempt_enable and use VM_FAULT_NOPAGE as failure code suggested by Yejian

v2:
- commit message changes suggested by Greg

v1: https://lore.kernel.org/lkml/CAJedcCzY72jqgF-pCPtx66vXXwdPn-KMagZnqrxcpWw1NxTLaA@mail.gmail.com/
---
 drivers/misc/sgi-gru/grufault.c  | 14 ++++++++++++--
 drivers/misc/sgi-gru/grumain.c   | 18 ++++++++++++++----
 drivers/misc/sgi-gru/grutables.h |  2 +-
 3 files changed, 27 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..77becb52f550 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 +938,13 @@ 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) {
+		preempt_enable();
+		mutex_unlock(&gts->ts_ctxlock);
+		gru_unload_context(gts, 1);
+		return VM_FAULT_NOPAGE;
+	}
 
 	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 v4] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Dimitri Sivanich]

On Wed, Oct 19, 2022 at 11:14:45AM +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.
> 
> Fixes: 55484c45dbec ("gru: allow users to specify gru chiplet 2")
> Reported-by: Zheng Wang <hackerzheng666@gmail.com>
> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> ---
> v4:
> - use VM_FAULT_NOPAGE as failure code in gru_fault and -EINVAL in other functions suggested by Yejian
> 
> v3:
> - add preempt_enable and use VM_FAULT_NOPAGE as failure code suggested by Yejian
> 
> v2:
> - commit message changes suggested by Greg
> 
> v1: https://lore.kernel.org/lkml/CAJedcCzY72jqgF-pCPtx66vXXwdPn-KMagZnqrxcpWw1NxTLaA@mail.gmail.com/
> ---
>  drivers/misc/sgi-gru/grufault.c  | 14 ++++++++++++--
>  drivers/misc/sgi-gru/grumain.c   | 18 ++++++++++++++----
>  drivers/misc/sgi-gru/grutables.h |  2 +-
>  3 files changed, 27 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);

In gru_set_context_option(), you are calling gru_unload_context() for all
non-zero 'ret' values, but there are other instances where non-zero 'ret'
values are being set that should not call gru_unload_context().  Maybe do
this instead:
			if (gru_check_context_placement(gts)) {
				gru_unlock_gts(gts);
				gru_unload_context(gts, 1);
				return -EINVAL;
			}

>  		}
>  		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..77becb52f550 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 +938,13 @@ 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) {

One suggestion, there is now no need to declare 'ret'.  Do this instead:
        if (gru_check_context_placement(gts)) {

> +		preempt_enable();
> +		mutex_unlock(&gts->ts_ctxlock);
> +		gru_unload_context(gts, 1);
> +		return VM_FAULT_NOPAGE;
> +	}
>  
>  	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 v4] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

Hi Dimitri Sivanich,

Sorry for my late reply. I was a little busy last week. I'll check the
code right now and let you know.

Thanks for your suggestion :)

Best Regards,
Zheng Wang

Dimitri Sivanich <sivanich@hpe.com> 于2022年10月19日周三 22:00写道：
>
> On Wed, Oct 19, 2022 at 11:14:45AM +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.
> >
> > Fixes: 55484c45dbec ("gru: allow users to specify gru chiplet 2")
> > Reported-by: Zheng Wang <hackerzheng666@gmail.com>
> > Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> > ---
> > v4:
> > - use VM_FAULT_NOPAGE as failure code in gru_fault and -EINVAL in other functions suggested by Yejian
> >
> > v3:
> > - add preempt_enable and use VM_FAULT_NOPAGE as failure code suggested by Yejian
> >
> > v2:
> > - commit message changes suggested by Greg
> >
> > v1: https://lore.kernel.org/lkml/CAJedcCzY72jqgF-pCPtx66vXXwdPn-KMagZnqrxcpWw1NxTLaA@mail.gmail.com/
> > ---
> >  drivers/misc/sgi-gru/grufault.c  | 14 ++++++++++++--
> >  drivers/misc/sgi-gru/grumain.c   | 18 ++++++++++++++----
> >  drivers/misc/sgi-gru/grutables.h |  2 +-
> >  3 files changed, 27 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);
>
> In gru_set_context_option(), you are calling gru_unload_context() for all
> non-zero 'ret' values, but there are other instances where non-zero 'ret'
> values are being set that should not call gru_unload_context().  Maybe do
> this instead:
>                         if (gru_check_context_placement(gts)) {
>                                 gru_unlock_gts(gts);
>                                 gru_unload_context(gts, 1);
>                                 return -EINVAL;
>                         }
>
> >               }
> >               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..77becb52f550 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 +938,13 @@ 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) {
>
> One suggestion, there is now no need to declare 'ret'.  Do this instead:
>         if (gru_check_context_placement(gts)) {
>
> > +             preempt_enable();
> > +             mutex_unlock(&gts->ts_ctxlock);
> > +             gru_unload_context(gts, 1);
> > +             return VM_FAULT_NOPAGE;
> > +     }
> >
> >       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 v4] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

[Zheng Hacker]

Dimitri Sivanich <sivanich@hpe.com> 于2022年10月19日周三 22:00写道：

> In gru_set_context_option(), you are calling gru_unload_context() for all
> non-zero 'ret' values, but there are other instances where non-zero 'ret'
> values are being set that should not call gru_unload_context().  Maybe do
> this instead:
>                         if (gru_check_context_placement(gts)) {
>                                 gru_unlock_gts(gts);
>                                 gru_unload_context(gts, 1);
>                                 return -EINVAL;
>                         }
>
> >               }
> >               break;
> >       case sco_gseg_owner:

Yes, that's correct. I'll fix it later.

> > @@ -727,14 +728,16 @@ void gru_check_context_placement(struct gru_thread_state *gts)
> >        */
> >       gru = gts->ts_gru;

> > -     gru_check_context_placement(gts);
> > +     ret = gru_check_context_placement(gts);
> > +     if (ret) {
>
> One suggestion, there is now no need to declare 'ret'.  Do this instead:
>         if (gru_check_context_placement(gts)) {
>
> > +             preempt_enable();
> > +             mutex_unlock(&gts->ts_ctxlock);
> > +             gru_unload_context(gts, 1);
> > +             return VM_FAULT_NOPAGE;
> > +     }
> >
> >       if (!gts->ts_gru) {
> >               STAT(load_user_context);

Get it! Thanks agagin for your advice :)

Regards,
Zheng Wang