Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0

[Christoph Hellwig]

On Wed, Dec 21, 2016 at 03:19:15PM -0800, Linus Torvalds wrote:
> Looking around a bit, the only even halfway suspicious scatterlist
> initialization thing I see is commit f9d03f96b988 ("block: improve
> handling of the magic discard payload") which used to have a magic
> hack wrt !bio->bi_vcnt, and that got removed. See __blk_bios_map_sg(),
> now it does __blk_bvec_map_sg() instead.

But that check was only for discard (and discard-like) bios which
had the maic single page that sometimes was unused attached.

For "normal" bios the for_each_segment loop iterates over bi_vcnt,
so it will be ignored anyway.  That being said both I and the lists
got CCed halfway through the thread and I haven't seen the original
report, so I'm not really sure what's going on here anyway.