On Thu, Apr 13, 2017 at 04:01:02PM -0700, Omar Sandoval wrote: > On Tue, Apr 11, 2017 at 01:58:37PM -0700, Bart Van Assche wrote: > > The blk-mq debugfs attributes are removed after blk_cleanup_queue() > > has finished. Since running a queue after a queue has entered the > > "dead" state is not allowed, disallow this. This patch avoids that > > an attempt to run a dead queue triggers a kernel crash. > > > > Signed-off-by: Bart Van Assche <[email protected]> > > Cc: Omar Sandoval <[email protected]> > > Cc: Hannes Reinecke <[email protected]> > > --- > > block/blk-mq-debugfs.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c > > index df9b688b877c..a1ce823578c7 100644 > > --- a/block/blk-mq-debugfs.c > > +++ b/block/blk-mq-debugfs.c > > @@ -111,6 +111,14 @@ static ssize_t blk_queue_flags_store(struct file > > *file, const char __user *ubuf, > > struct request_queue *q = file_inode(file)->i_private; > > char op[16] = { }, *s; > > > > + /* > > + * The debugfs attributes are removed after blk_cleanup_queue() has > > + * called blk_mq_free_queue(). Return if QUEUE_FLAG_DEAD has been set > > + * to avoid triggering a use-after-free. > > + */ > > + if (blk_queue_dead(q)) > > + return -ENOENT; > > + > > len = min(len, sizeof(op) - 1); > > if (copy_from_user(op, ubuf, len)) > > return -EFAULT; > > -- > > 2.12.0 > > > > Hi, Bart, > > Looking at this, I think we have similar issues with most of the other > debugfs files. Should we move the debugfs cleanup earlier?
In particular, I think we can call blk_mq_debugfs_unregister_hctxs() (which is somewhat poorly named, as it removes the whole mq directory) before we call blk_mq_free_queue(). I was under the impression that that's what it already did, but I think I was wrong.
