Re: kintegrityd workqueue fix backported, but only to some LTS

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Mar 14, 2022 at 03:48:59PM +0000, Niklas Cassel wrote:
> On Mon, Mar 14, 2022 at 02:54:50PM +0100, Greg KH wrote:
> > On Mon, Mar 14, 2022 at 01:08:57PM +0000, Niklas Cassel wrote:
> > > On Mon, Mar 14, 2022 at 01:28:38PM +0100, Greg KH wrote:
> > > > On Mon, Mar 14, 2022 at 11:50:18AM +0000, Niklas Cassel wrote:
> > > > > Hello Christoph, stable,
> > > > > 
> > > > > I recently saw a crash caused by the kintegrityd workqueue that could only
> > > > > be reproduced on older kernels.
> > > > > A null pointer dereference in function bio_integrity_verify_fn.
> > > > > 
> > > > > The fix in Linus's tree for this:
> > > > > 3df49967f6f1 ("block: flush the integrity workqueue in blk_integrity_unregister")
> > > > > was first merged in v5.15.
> > > > > 
> > > > > The fix has been backported to v5.10 LTS branch in:
> > > > > 1ef68b84bc11 ("block: flush the integrity workqueue in blk_integrity_unregister")
> > > > > 
> > > > > The fix doesn't have a fixes tag, but from inspecting the code,
> > > > > I don't understand why this was only backported to v5.10, AFAICT it should
> > > > > at least have been backported to v5.4, v4.19 and v4.14 LTS as well.
> > > > > 
> > > > > Original series:
> > > > > https://lore.kernel.org/all/20210914070657.87677-3-hch@lst.de/
> > > > > 
> > > > > The blk_flush_integrity() call that actually fixes the crash should be
> > > > > trivial to backport/add before clearing the flag and doing the memset.
> > > > 
> > > > A backported patch series would be great to have, to show that you have
> > > > tested that it works properly.
> > > 
> > > Hello Greg,
> > > 
> > > Unfortunately, I don't have access to the machine. I was only provided
> > > a kernel crash dump to diagnose the crash.
> > > 
> > > I guess I was hoping for someone more familiar with the integrity stuff
> > > to backport it. Both patch 1 and 3 are unrelated to the NULL pointer crash,
> > > and because of various refactoring, I'm not sure if patch 1 and 3 are even
> > > applicable for older kernel versions.
> > 
> > I do not know what patch 1 and 3 refer to here, sorry :(
> 
> Sorry, I was referring to patch 1/3 and 3/3 in the series:
> https://lore.kernel.org/all/20210914070657.87677-1-hch@lst.de/
> 
> Looking at it again, patch 1/2 and 2/2 are both required.
> 
> Patch 3/3, I don't know, since the flag used to be in bdi, but is now in
> request_queue.
> 
> But even then, since this doesn't have a Fixes tag, I'm not sure how far
> this has to be backported. Christoph, thoughts?
> 
> I'm assuming that it was the machine learning scripts that backported it to
> 5.10, but considering that I've seen a crash dump with this in 4.18, it
> definitely should have been backported to 4.19+ (but probably even further
> back).

Please test and if it works for you, provide a backported series and I
will be glad to consider it.

thanks,

greg k-h