From: WangJinchao wangjinchao@xfusion.com

stable inclusion from stable-v5.10.201 commit 41aad9d6953984d134fc50f631f24ef476875d4d category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9RQM3 CVE: CVE-2023-52854

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ 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 Signed-off-by: sanglipeng sanglipeng1@jd.com Signed-off-by: Zheng Zucheng zhengzucheng@huawei.com --- kernel/padata.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/padata.c b/kernel/padata.c index 5cf16ee498e2..e270bb9e18ff 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);