Re: 4.12 NULL pointer dereference in kmem_cache_free on USB storage removal

[Bart Van Assche]

On Wed, 2017-07-19 at 08:13 +0300, Yagmur Oymak wrote:
> On 07/14/2017 12:07 AM, Bart Van Assche wrote:
> > On Thu, 2017-07-13 at 23:24 +0300, Meelis Roos wrote:
> > > [258062.320700] RIP: 0010:kmem_cache_free+0x12/0x160
> > > [258062.320886] Call Trace:
> > > [258062.320897]  scsi_exit_rq+0x4d/0x60
> > > [258062.320909]  free_request_size+0x1c/0x30
> > > [258062.320923]  mempool_destroy+0x1d/0x60
> > > [258062.320935]  blk_exit_rl+0x1b/0x40
> > > [258062.320946]  __blk_release_queue+0x7d/0x120
> > > [258062.320959]  process_one_work+0x1af/0x340
> > > [258062.320972]  worker_thread+0x43/0x3e0
> > > [258062.320984]  kthread+0xfe/0x130
> > > [258062.320995]  ? create_worker+0x170/0x170
> > > [258062.321007]  ? kthread_create_on_node+0x40/0x40
> > > [258062.321022]  ret_from_fork+0x22/0x30
> > 
> > Thank you for your report. Can you apply commit 8e6882545d8c ("scsi: Avoid
> > that scsi_exit_rq() triggers a use-after-free") on top of kernel v4.12 and
> > retest? That commit has been tagged "Cc: stable" so I hope that this patch
> > will be included in kernel v4.12.1. However, that kernel is not yet available
> > unfortunately ...
> 
> That patch fixes the problem, as far as I tested. However, it still is
> not included in stable by 4.12.2. The problem persists there, and is
> fixed when this patch is applied on top of it. What to to about it? 
 
Hello Yagmur,

[ Please don't top-post -- this is considered annoying in the Linux community ]

Since kernel v4.13-rc1 has been released and since commit 8e6882545d8c is included
in v4.13-rc1 I assume that it won't take long before a stable kernel is released
that includes that commit. BTW, Greg just announced that that commit will be included
in the next v4.11 stable kernel. See also https://lkml.org/lkml/2017/7/19/494.

Bart.