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Subject[PATCH for 4.19-stable] padata: fix null pointer deref of pd->pinst
Date
The 4.19 backport dc34710a7aba ("padata: Remove broken queue flushing")
removed padata_alloc_pd()'s assignment to pd->pinst, resulting in:

Unable to handle kernel NULL pointer dereference ...
...
pc : padata_reorder+0x144/0x2e0
...
Call trace:
padata_reorder+0x144/0x2e0
padata_do_serial+0xc8/0x128
pcrypt_aead_enc+0x60/0x70 [pcrypt]
padata_parallel_worker+0xd8/0x138
process_one_work+0x1bc/0x4b8
worker_thread+0x164/0x580
kthread+0x134/0x138
ret_from_fork+0x10/0x18

This happened because the backport was based on an enhancement that
moved this assignment but isn't in 4.19:

bfde23ce200e ("padata: unbind parallel jobs from specific CPUs")

Simply restore the assignment to fix the crash.

Fixes: dc34710a7aba ("padata: Remove broken queue flushing")
Reported-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
---
kernel/padata.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/padata.c b/kernel/padata.c
index 11c5f9c8779e..cfab62923c45 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -510,6 +510,7 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
atomic_set(&pd->seq_nr, -1);
atomic_set(&pd->reorder_objects, 0);
atomic_set(&pd->refcnt, 1);
+ pd->pinst = pinst;
spin_lock_init(&pd->lock);

return pd;
--
2.25.0
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