| Message ID | ZRTLHY5A+VqIKhA2@fedora |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] padata: Fix the UAF issue related to parallel_data | expand |
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 >
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 > >
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 --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);
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(-)