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`.
Fixes: 07928d9bfc81 ("padata: Remove broken queue flushing")
Signed-off-by: WangJinchao <[email protected]>
Acked-by: Daniel Jordan <[email protected]>
---
V4:
Included Daniel's ack
Included Herbert's ack
V3: https://lore.kernel.org/all/ZSDWAcUxXcwD4YUZ@fedora/
Included Daniel's ack
introduced wrong patch
V2: https://lore.kernel.org/all/ZRTLHY5A+VqIKhA2@fedora/
To satisfy Sparse, use rcu_dereference_protected.
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
V1: https://lore.kernel.org/all/ZRE4XvOOhz4HSOgR@fedora/
kernel/padata.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/padata.c b/kernel/padata.c
index 222d60195de6..73108ac75f03 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -1102,12 +1102,15 @@ EXPORT_SYMBOL(padata_alloc_shell);
*/
void padata_free_shell(struct padata_shell *ps)
{
+ struct parallel_data *pd;
if (!ps)
return;
mutex_lock(&ps->pinst->lock);
list_del(&ps->list);
- padata_free_pd(rcu_dereference_protected(ps->pd, 1));
+ 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 Fri, Oct 20, 2023 at 01:03:59PM +0800, Herbert Xu wrote:
> WangJinchao <[email protected]> wrote:
> > diff --git a/kernel/padata.c b/kernel/padata.c
> > index 222d60195de6..73108ac75f03 100644
> > --- a/kernel/padata.c
> > +++ b/kernel/padata.c
> > @@ -1102,12 +1102,15 @@ EXPORT_SYMBOL(padata_alloc_shell);
> > */
> > void padata_free_shell(struct padata_shell *ps)
> > {
> > + struct parallel_data *pd;
> > if (!ps)
> > return;
The \n after the declaration disappeared in this version but would be
nice for consistency with the file. Maybe when applying, no need for
another post.
> Daniel, could you please reconfirm that you're still with v4?
Yes, regardless of above,
Acked-by: Daniel Jordan <[email protected]>
WangJinchao <[email protected]> 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`.
>
> Fixes: 07928d9bfc81 ("padata: Remove broken queue flushing")
>
> Signed-off-by: WangJinchao <[email protected]>
> Acked-by: Daniel Jordan <[email protected]>
> ---
> V4:
> Included Daniel's ack
> Included Herbert's ack
> V3: https://lore.kernel.org/all/ZSDWAcUxXcwD4YUZ@fedora/
> Included Daniel's ack
> introduced wrong patch
> V2: https://lore.kernel.org/all/ZRTLHY5A+VqIKhA2@fedora/
> To satisfy Sparse, use rcu_dereference_protected.
> Reported-by: kernel test robot <[email protected]>
> Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
>
> V1: https://lore.kernel.org/all/ZRE4XvOOhz4HSOgR@fedora/
> kernel/padata.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt