On Sun, Apr 19, 2020 at 08:29:21AM -0700, Bart Van Assche wrote: > On 4/19/20 12:58 AM, Christoph Hellwig wrote: >> On Sat, Apr 18, 2020 at 08:40:20AM -0700, Bart Van Assche wrote: >>>> This can have a sideeffect not only bdi->dev_name will be truncated to 64 >>>> chars (which generally doesn't matter) but possibly also kobject name will >>>> be truncated in the same way. Which may have user visible effects. E.g. >>>> for fs/vboxsf 64 chars need not be enough. So shouldn't we rather do it the >>>> other way around - i.e., let device_create_vargs() create the device name >>>> and then copy to bdi->dev_name whatever fits? >>> >>> How about using kvasprintf() instead of vsnprintf()? >> >> That is what v1 did, see the thread in response to that on why it isn't >> a good idea. > > Are you perhaps referring to patch "[PATCH 3/8] bdi: add a ->dev_name field > to struct backing_dev_info" > (https://lore.kernel.org/linux-block/20200416071519.807660-4-hch@xxxxxx/) > and also to the replies to that patch? This is what I found in the replies: > "When driver try to to re-register bdi but without release_bdi(), the old > dev_name will be cover directly by the newer in bdi_register_va(). So, I am > not sure whether it can cause memory leak for bdi->dev_name." > > Has it been considered to avoid that leak by freeing bdi->dev_name from > unregister_bdi(), e.g. as follows? We'd need some protection against concurrent accesses as unregister_bdi can race with them. But with RCU that could be handled, so let me try that.
