[Samba] io_uring cause data corruption

[Jeremy Allison]

On Thu, Apr 30, 2020 at 10:25:49AM +0200, A L wrote:

> So I did some more tests. smbclient mget does not copy in the same way
> Windows Explorer does. When copying in Windows Explorer, there are many
> multiple concurrent threads used to transfer the files. With smbclient mget
> there are no corruptions, both locally and over the network from another
> Linux machine.
> 
> I analysed the difference between a correct file and a corrupt file.
> At position 0x7A0000 the corrupt file started to contain only binary zero.
> At position 0x800000 the zeroes ended and correct data continued. To me it
> sound like some wrong memory is copied somehow.
> 
> These two files shows the difference as shown in a hex-editor.
> https://paste.tnonline.net/files/MO1FJvDOG6E8_smb_1
> https://paste.tnonline.net/files/Rglite4KWmU8_smb_2

Is it always the same area in the file that is corrupt ?
The fact that it's on a 4K page-aligned boundary is
interesting. If you can corrolate I'd love to see
the SMB2 traffic on the wire that corresponds to the
corrupted data write/read.