On Wed 17-03-21 15:56:44, Greg KH wrote: > On Wed, Mar 17, 2021 at 03:44:16PM +0100, Michal Hocko wrote: > > On Wed 17-03-21 14:34:27, Greg KH wrote: > > > On Wed, Mar 17, 2021 at 01:08:21PM +0100, Michal Hocko wrote: > > > > Btw. I still have problems with the approach. seq_file is intended to > > > > provide safe way to dump values to the userspace. Sacrificing > > > > performance just because of some abuser seems like a wrong way to go as > > > > Al pointed out earlier. Can we simply stop the abuse and disallow to > > > > manipulate the buffer directly? I do realize this might be more tricky > > > > for reasons mentioned in other emails but this is definitely worth > > > > doing. > > > > > > We have to provide a buffer to "write into" somehow, so what is the best > > > way to stop "abuse" like this? > > > > What is wrong about using seq_* interface directly? > > Right now every show() callback of sysfs would have to be changed :( Is this really the case? Would it be too ugly to have an intermediate buffer and then seq_puts it into the seq file inside sysfs_kf_seq_show. Sure one copy more than necessary but it this shouldn't be a hot path or even visible on small strings. So that might be worth destroying an inherently dangerous seq API (seq_get_buf). -- Michal Hocko SUSE Labs
