diff mbox series

[v2] padata: Fix the UAF issue related to parallel_data

Message ID ZRTLHY5A+VqIKhA2@fedora
State New
Headers
Series [v2] padata: Fix the UAF issue related to parallel_data |

Commit Message

Wang Jinchao Sept. 28, 2023, 12:38 a.m. UTC 
  In a high-load arm64 environment, the pcrypt_aead01 test in LTP can lead to
system UAF (Use-After-Free) issues. Due to the lengthy analysis of the
pcrypt_aead01 function call, I'll describe the problem scenario using a
simplified model:

Suppose there's a user of padata named `user_function` that adheres to
the padata requirement of calling `padata_free_shell` after `serial()`
has been invoked, as demonstrated in the following code:

```c
struct request {
    struct padata_priv padata;
    struct completion *done;
};

void parallel(struct padata_priv *padata) {
    do_something();
}

void serial(struct padata_priv *padata) {
    struct request *request = container_of(padata, struct request, padata);
    complete(request->done);
}

void user_function() {
    DECLARE_COMPLETION(done)
    padata->parallel = parallel;
    padata->serial = serial;
    padata_do_parallel();
    wait_for_completion(&done);
    padata_free_shell();
}
```

In the corresponding padata.c file, there's the following code:

```c
static void padata_serial_worker(struct work_struct *serial_work) {
    ...
    cnt = 0;

    while (!list_empty(&local_list)) {
        ...
        padata->serial(padata);
        cnt++;
    }

    local_bh_enable();

    if (refcount_sub_and_test(cnt, &pd->refcnt))
        padata_free_pd(pd);
}
```

Because of the high system load and the accumulation of unexecuted
softirq at this moment, `local_bh_enable()` in padata takes longer
to execute than usual. Subsequently, when accessing `pd->refcnt`,
`pd` has already been released by `padata_free_shell()`, resulting
in a UAF issue with `pd->refcnt`.

The fix is straightforward: add `refcount_dec_and_test` before calling
`padata_free_pd` in `padata_free_shell`.

Signed-off-by: Wang Jinchao <wangjinchao@xfusion.com>
---
V2:
    To satisfy Sparse, use rcu_dereference_protected.
    Reported-by: kernel test robot <lkp@intel.com>
    Closes: https://lore.kernel.org/oe-kbuild-all/202309270829.xHgTOMKw-lkp@intel.com/

V1: https://lore.kernel.org/all/ZRE4XvOOhz4HSOgR@fedora/

 kernel/padata.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Daniel Jordan Oct. 4, 2023, 2:54 p.m. UTC | #1 
On Thu, Sep 28, 2023 at 08:38:53AM +0800, Wang Jinchao wrote:
> In a high-load arm64 environment, the pcrypt_aead01 test in LTP can lead to
> system UAF (Use-After-Free) issues. Due to the lengthy analysis of the
> pcrypt_aead01 function call, I'll describe the problem scenario using a
> simplified model:
> 
> Suppose there's a user of padata named `user_function` that adheres to
> the padata requirement of calling `padata_free_shell` after `serial()`
> has been invoked, as demonstrated in the following code:
> 
> ```c
> struct request {
>     struct padata_priv padata;
>     struct completion *done;
> };
> 
> void parallel(struct padata_priv *padata) {
>     do_something();
> }
> 
> void serial(struct padata_priv *padata) {
>     struct request *request = container_of(padata, struct request, padata);
>     complete(request->done);
> }
> 
> void user_function() {
>     DECLARE_COMPLETION(done)
>     padata->parallel = parallel;
>     padata->serial = serial;
>     padata_do_parallel();
>     wait_for_completion(&done);
>     padata_free_shell();
> }
> ```
> 
> In the corresponding padata.c file, there's the following code:
> 
> ```c
> static void padata_serial_worker(struct work_struct *serial_work) {
>     ...
>     cnt = 0;
> 
>     while (!list_empty(&local_list)) {
>         ...
>         padata->serial(padata);
>         cnt++;
>     }
> 
>     local_bh_enable();
> 
>     if (refcount_sub_and_test(cnt, &pd->refcnt))
>         padata_free_pd(pd);
> }
> ```
> 
> Because of the high system load and the accumulation of unexecuted
> softirq at this moment, `local_bh_enable()` in padata takes longer
> to execute than usual. Subsequently, when accessing `pd->refcnt`,
> `pd` has already been released by `padata_free_shell()`, resulting
> in a UAF issue with `pd->refcnt`.
> 
> The fix is straightforward: add `refcount_dec_and_test` before calling
> `padata_free_pd` in `padata_free_shell`.

This could use a Fixes tag.  From Nicolai's patch[0] we agreed on

Fixes: 07928d9bfc81 ("padata: Remove broken queue flushing")

With that,

Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>

Thanks!

[0] https://lore.kernel.org/all/87educb7rm.fsf@suse.de/

> Signed-off-by: Wang Jinchao <wangjinchao@xfusion.com>
> ---
> V2:
>     To satisfy Sparse, use rcu_dereference_protected.
>     Reported-by: kernel test robot <lkp@intel.com>
>     Closes: https://lore.kernel.org/oe-kbuild-all/202309270829.xHgTOMKw-lkp@intel.com/
> 
> V1: https://lore.kernel.org/all/ZRE4XvOOhz4HSOgR@fedora/
> 
>  kernel/padata.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/padata.c b/kernel/padata.c
> index 222d60195de6..acef1e703a8b 100644
> --- a/kernel/padata.c
> +++ b/kernel/padata.c
> @@ -1107,7 +1107,9 @@ void padata_free_shell(struct padata_shell *ps)
>  
>  	mutex_lock(&ps->pinst->lock);
>  	list_del(&ps->list);
> -	padata_free_pd(rcu_dereference_protected(ps->pd, 1));
> +	struct parallel_data *pd = rcu_dereference_protected(ps->pd, 1);
> +	if (refcount_dec_and_test(&pd->refcnt))
> +		padata_free_pd(pd);
>  	mutex_unlock(&ps->pinst->lock);
>  
>  	kfree(ps);
> -- 
> 2.40.0
>
Daniel Jordan Oct. 4, 2023, 7:07 p.m. UTC | #2 
On Wed, Oct 04, 2023 at 10:54:29AM -0400, Daniel Jordan wrote:
> On Thu, Sep 28, 2023 at 08:38:53AM +0800, Wang Jinchao wrote:
> > In a high-load arm64 environment, the pcrypt_aead01 test in LTP can lead to
> > system UAF (Use-After-Free) issues. Due to the lengthy analysis of the
> > pcrypt_aead01 function call, I'll describe the problem scenario using a
> > simplified model:
> > 
> > Suppose there's a user of padata named `user_function` that adheres to
> > the padata requirement of calling `padata_free_shell` after `serial()`
> > has been invoked, as demonstrated in the following code:
> > 
> > ```c
> > struct request {
> >     struct padata_priv padata;
> >     struct completion *done;
> > };
> > 
> > void parallel(struct padata_priv *padata) {
> >     do_something();
> > }
> > 
> > void serial(struct padata_priv *padata) {
> >     struct request *request = container_of(padata, struct request, padata);
> >     complete(request->done);
> > }
> > 
> > void user_function() {
> >     DECLARE_COMPLETION(done)
> >     padata->parallel = parallel;
> >     padata->serial = serial;
> >     padata_do_parallel();
> >     wait_for_completion(&done);
> >     padata_free_shell();
> > }
> > ```
> > 
> > In the corresponding padata.c file, there's the following code:
> > 
> > ```c
> > static void padata_serial_worker(struct work_struct *serial_work) {
> >     ...
> >     cnt = 0;
> > 
> >     while (!list_empty(&local_list)) {
> >         ...
> >         padata->serial(padata);
> >         cnt++;
> >     }
> > 
> >     local_bh_enable();
> > 
> >     if (refcount_sub_and_test(cnt, &pd->refcnt))
> >         padata_free_pd(pd);
> > }
> > ```
> > 
> > Because of the high system load and the accumulation of unexecuted
> > softirq at this moment, `local_bh_enable()` in padata takes longer
> > to execute than usual. Subsequently, when accessing `pd->refcnt`,
> > `pd` has already been released by `padata_free_shell()`, resulting
> > in a UAF issue with `pd->refcnt`.
> > 
> > The fix is straightforward: add `refcount_dec_and_test` before calling
> > `padata_free_pd` in `padata_free_shell`.
> 
> This could use a Fixes tag.  From Nicolai's patch[0] we agreed on
> 
> Fixes: 07928d9bfc81 ("padata: Remove broken queue flushing")
> 
> With that,
> 
> Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>
> 
> Thanks!
> 
> [0] https://lore.kernel.org/all/87educb7rm.fsf@suse.de/
> 
> > Signed-off-by: Wang Jinchao <wangjinchao@xfusion.com>
> > ---
> > V2:
> >     To satisfy Sparse, use rcu_dereference_protected.
> >     Reported-by: kernel test robot <lkp@intel.com>
> >     Closes: https://lore.kernel.org/oe-kbuild-all/202309270829.xHgTOMKw-lkp@intel.com/
> > 
> > V1: https://lore.kernel.org/all/ZRE4XvOOhz4HSOgR@fedora/
> > 
> >  kernel/padata.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/padata.c b/kernel/padata.c
> > index 222d60195de6..acef1e703a8b 100644
> > --- a/kernel/padata.c
> > +++ b/kernel/padata.c
> > @@ -1107,7 +1107,9 @@ void padata_free_shell(struct padata_shell *ps)
> >  
> >  	mutex_lock(&ps->pinst->lock);
> >  	list_del(&ps->list);
> > -	padata_free_pd(rcu_dereference_protected(ps->pd, 1));
> > +	struct parallel_data *pd = rcu_dereference_protected(ps->pd, 1);

Oh, I should've also said please move the declaration of pd to the top
of the function like scripts/checkpatch.pl suggests.

> > +	if (refcount_dec_and_test(&pd->refcnt))
> > +		padata_free_pd(pd);
> >  	mutex_unlock(&ps->pinst->lock);
> >  
> >  	kfree(ps);
> > -- 
> > 2.40.0
> >
Wang Jinchao Oct. 7, 2023, 4:01 a.m. UTC | #3 
On Wed, Oct 04, 2023 at 03:07:10PM -0400, Daniel Jordan wrote:
> On Wed, Oct 04, 2023 at 10:54:29AM -0400, Daniel Jordan wrote:
> > On Thu, Sep 28, 2023 at 08:38:53AM +0800, Wang Jinchao wrote:
...
> > This could use a Fixes tag.  From Nicolai's patch[0] we agreed on
> > 
> > Fixes: 07928d9bfc81 ("padata: Remove broken queue flushing")
> > 
> > With that,
> > 
> > Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>
> > 
> > Thanks!
> > 
...
> 
> Oh, I should've also said please move the declaration of pd to the top
> of the function like scripts/checkpatch.pl suggests.
> 
> > > +	if (refcount_dec_and_test(&pd->refcnt))
> > > +		padata_free_pd(pd);
> > >  	mutex_unlock(&ps->pinst->lock);
> > >  
> > >  	kfree(ps);
> > > -- 
> > > 2.40.0
> > > 
Thanks for suggestion, both were updated in V3.
V3: https://lore.kernel.org/all/ZSDWAcUxXcwD4YUZ@fedora/
diff mbox series

Patch

diff --git a/kernel/padata.c b/kernel/padata.c
index 222d60195de6..acef1e703a8b 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -1107,7 +1107,9 @@  void padata_free_shell(struct padata_shell *ps)
 
 	mutex_lock(&ps->pinst->lock);
 	list_del(&ps->list);
-	padata_free_pd(rcu_dereference_protected(ps->pd, 1));
+	struct parallel_data *pd = rcu_dereference_protected(ps->pd, 1);
+	if (refcount_dec_and_test(&pd->refcnt))
+		padata_free_pd(pd);
 	mutex_unlock(&ps->pinst->lock);
 
 	kfree(ps);