Re: [PATCH] Resolve data corruption of TCP server info fields

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Hi Rohith,

Thanks for catching the problem and proposing the patch!

I think there is a problem with just removing server->total_read
updates inside decrypt_raw_data():

The same function is used in receive_encrypted_standard() which then
calls cifs_handle_standard(). The latter uses server->total_read in at
least two places: in server->ops->check_message and cifs_dump_mem().

There may be other places in the code that assume server->total_read
to be correct. I would avoid simply removing this in all code paths
and would rather make a more specific fix for the offloaded reads.

--
Best regards,
Pavel Shilovsky

чт, 8 окт. 2020 г. в 13:36, Steve French <smfrench@xxxxxxxxx>:
>
> Fixed up 2 small checkpatch warnings and merged into cifs-2.6.git for-next
>
> On Thu, Oct 8, 2020 at 9:40 AM Rohith Surabattula
> <rohiths.msft@xxxxxxxxx> wrote:
> >
> > Hi All,
> >
> > With the "esize" mount option, I observed data corruption and cifs
> > reconnects during performance tests.
> >
> > TCP server info field server->total_read is modified parallely by
> > demultiplex thread and decrypt offload worker thread. server->total_read
> > is used in calculation to discard the remaining data of PDU which is
> > not read into memory.
> >
> > Because of parallel modification, “server->total_read” value got
> > corrupted and instead of discarding the remaining data, it discarded
> > some valid data from the next PDU.
> >
> > server->total_read field is already updated properly during read from
> > socket. So, no need to update the same field again after decryption.
> >
> > Regards,
> > Rohith
>
>
>
> --
> Thanks,
>
> Steve




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