Re: [PATCH 5.17 000/772] 5.17.14-rc1 review

[Greg Kroah-Hartman]

On Sat, Jun 18, 2022 at 07:57:01PM +0800, Coly Li wrote:
> 
> 
> > 2022年6月18日 19:37，Pavel Machek <pavel@xxxxxx> 写道：
> > 
> > Hi!
> > 
> >>>>   Fixes: bc082a55d25c ("bcache: fix inaccurate io state for detached
> >>> ...
> >>> 
> >>>> +++ b/drivers/md/bcache/request.c
> >>>> @@ -1107,6 +1107,12 @@ static void detached_dev_do_request(struct
> >>>> bcache_device *d, struct bio *bio,
> >>>>        * which would call closure_get(&dc->disk.cl)
> >>>>        */
> >>>>       ddip = kzalloc(sizeof(struct detached_dev_io_private), GFP_NOIO);
> >>>> +       if (!ddip) {
> >>>> +               bio->bi_status = BLK_STS_RESOURCE;
> >>>> +               bio->bi_end_io(bio);
> >>>> +               return;
> >>>> +       }
> >>>> +
> >>>>       ddip->d = d;
> >>>>       /* Count on the bcache device */
> >>>>       ddip->orig_bdev = orig_bdev;
> >>>> 
> >>> 
> >>> So... for patch to make any difference, memory allocation has to fail
> >>> and ddip has to be NULL.
> >>> 
> >>> Before the patch, it would oops in "ddip->d = d;". With the patch, you
> >>> do some kind of error handling. Even if it is buggy, it should not do
> >>> more harm than immediate oops.
> >> 
> >> I just receive this single email and don’t have any idea for the context and what the problem is. Where can I see the whole conversation?
> >> 
> > 
> > Discussion happened on stable@xxxxxxxxxxxxxxx mailing lists, archives
> > should be easily available. Copy went to lkml, too.
> 
> Hi Pavel and Greg,
> 
> Thanks for the hint, I see the context. I cannot tell the direct reason of the kfence regression, but it is worthy to have this patch in,
> - commit 7d6b902ea0e0 ("bcache: memset on stack variables in bch_btree_check() and bch_sectors_dirty_init()”)
> 
> I am not sure whether it is directly related to the kfence issue, it corrects potential unexpected stack state in some condition. Hope it may help a bit.

Added where?

confused,

greg k-h