6.6-stable review patch. If anyone has any objections, please let me know.
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From: WangJinchao wangjinchao@xfusion.com
[ Upstream commit 7ddc21e317b360c3444de3023bcc83b85fabae2f ]
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 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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/padata.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/padata.c b/kernel/padata.c index 222d60195de66..ff349e1084c1d 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -1102,12 +1102,16 @@ 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);