| Message ID | ZRE4XvOOhz4HSOgR@fedora |
|---|---|
| State | New |
| Headers | show |
| Series | padata: Fix the UAF issue related to parallel_data | expand |
diff --git a/kernel/padata.c b/kernel/padata.c index 222d60195de6..15dbcf7ce623 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -1107,7 +1107,8 @@ 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)); + if (refcount_dec_and_test(&ps->pd->refcnt)) + padata_free_pd(rcu_dereference_protected(ps->pd, 1)); 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_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> --- kernel/padata.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)