Miklos Szeredi wrote: > On Thu, May 10, 2018 at 10:07 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > On Wed, May 09, 2018 at 07:58:58PM +0900, Tetsuo Handa wrote: > >> >From 9f41081f8bd6762a6f629e5e23e6d07a62bba69c Mon Sep 17 00:00:00 2001 > >> From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> > >> Date: Sat, 28 Apr 2018 11:24:09 +0900 > >> Subject: [PATCH] fuse: don't keep inode-less dentry at fuse_ctl_add_dentry(). > >> > >> syzbot is reporting NULL pointer dereference at fuse_ctl_remove_conn() [1]. > >> Since fc->ctl_ndents is incremented by fuse_ctl_add_conn() when new_inode() > >> failed, fuse_ctl_remove_conn() reaches an inode-less dentry and tries to > >> clear d_inode(dentry)->i_private field. Fix this by calling dput() rather > >> than incrementing fc->ctl_ndents when new_inode() failed. > > > > That looks bloody awful. Sure, everything that accesses fc->ctl_dentry is > > synchronous with this, but it would've been much easier to follow if > > shoving dentry into that array happened only after it's been fully set > > up. > > > > Incidentally, there's a nasty headache waiting to happen in that code - > > consider a twit mounting something on that. And think what happens when > > connection gets shut down... > > Need to call d_invalidate() instead of d_drop() in there. Is that > what you are referring to? > > Thanks, > Miklos > I couldn't catch what Al is worrying about. I assumed that dput() is fine because proc_setup_thread_self() in fs/proc/thread_self.c is doing dput() when new_inode_pseudo() failed after d_alloc_name().
