On Wed, Sep 25, 2024 at 01:15:16PM GMT, Jan Kara wrote: > On Wed 25-09-24 11:05:16, Christian Brauner wrote: > > Epoll relies on a racy fastpath check during __fput() in > > eventpoll_release() to avoid the hit of pointlessly acquiring a > > semaphore. Annotate that race by using WRITE_ONCE() and READ_ONCE(). > > > > Link: https://lore.kernel.org/r/66edfb3c.050a0220.3195df.001a.GAE@xxxxxxxxxx > > Reported-by: syzbot+3b6b32dc50537a49bb4a@xxxxxxxxxxxxxxxxxxxxxxxxx > > Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> > > --- > > fs/eventpoll.c | 3 ++- > > include/linux/eventpoll.h | 2 +- > > 2 files changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/fs/eventpoll.c b/fs/eventpoll.c > > index f53ca4f7fced..fa766695f886 100644 > > --- a/fs/eventpoll.c > > +++ b/fs/eventpoll.c > > @@ -823,7 +823,8 @@ static bool __ep_remove(struct eventpoll *ep, struct epitem *epi, bool force) > > to_free = NULL; > > head = file->f_ep; > > if (head->first == &epi->fllink && !epi->fllink.next) { > > - file->f_ep = NULL; > > + /* See eventpoll_release() for details. */ > > + WRITE_ONCE(file->f_ep, NULL); > > There's one more write to file->f_ep in attach_epitem() which needs > WRITE_ONCE() as well to match the READ_ONCE() in other places. Otherwise Thanks, done! > feel free to add: > > Reviewed-by: Jan Kara <jack@xxxxxxx> Thanks!
