On Wed, Jan 22, 2020 at 08:13:12AM -0800, Linus Torvalds wrote: > On Wed, Jan 22, 2020 at 5:00 AM Christophe Leroy > <christophe.leroy@xxxxxx> wrote: > > > > Modify filldir() and filldir64() to request the real area they need > > to get access to. > > Not like this. > > This makes the situation for architectures like x86 much worse, since > you now use "put_user()" for the previous dirent filling. Which does > that expensive user access setup/teardown twice again. > > So either you need to cover both the dirent's with one call, or you > just need to cover the whole (original) user buffer passed in. But not > this unholy mixing of both unsafe_put_user() and regular put_user(). I would suggest simply covering the range from dirent->d_off to buf->current_dir->d_name[namelen]; they are going to be close to each other and we need those addresses anyway...
