Re: [PATCH for 4.19-stable] padata: fix null pointer deref of pd->pinst

[Greg Kroah-Hartman]

On Fri, Feb 14, 2020 at 01:28:21PM -0500, Daniel Jordan wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: Sasha Levin <sashal@xxxxxxxxxx>
> Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>  kernel/padata.c | 1 +
>  1 file changed, 1 insertion(+)

Thanks for this, now queued up.

greg k-h