padata: Fix refcnt handling in padata_free_shell()
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: 07928d9bfc
("padata: Remove broken queue flushing")
Signed-off-by: WangJinchao <wangjinchao@xfusion.com>
Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
parent
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@ -1102,12 +1102,16 @@ EXPORT_SYMBOL(padata_alloc_shell);
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*/
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*/
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void padata_free_shell(struct padata_shell *ps)
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void padata_free_shell(struct padata_shell *ps)
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{
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{
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struct parallel_data *pd;
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if (!ps)
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if (!ps)
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return;
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return;
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mutex_lock(&ps->pinst->lock);
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mutex_lock(&ps->pinst->lock);
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list_del(&ps->list);
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list_del(&ps->list);
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padata_free_pd(rcu_dereference_protected(ps->pd, 1));
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pd = rcu_dereference_protected(ps->pd, 1);
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if (refcount_dec_and_test(&pd->refcnt))
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padata_free_pd(pd);
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mutex_unlock(&ps->pinst->lock);
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mutex_unlock(&ps->pinst->lock);
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kfree(ps);
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kfree(ps);
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