Re: [PATCH v4] proc: report open files as size in stat() for /proc/pid/fd

[Brian Foster <bfoster@redhat.com>]

On Fri, Nov 18, 2022 at 11:18:36AM -0800, Ivan Babrou wrote:
> On Fri, Nov 18, 2022 at 11:10 AM Brian Foster <bfoster@redhat.com> wrote:
> > > +static int proc_fd_getattr(struct user_namespace *mnt_userns,
> > > +                     const struct path *path, struct kstat *stat,
> > > +                     u32 request_mask, unsigned int query_flags)
> > > +{
> > > +     struct inode *inode = d_inode(path->dentry);
> > > +     int rv = 0;
> > > +
> > > +     generic_fillattr(&init_user_ns, inode, stat);
> > > +
> >
> > Sorry I missed this on v3, but shouldn't this pass through the
> > mnt_userns parameter?
> 
> The mnt_userns parameter was added in 549c729 (fs: make helpers idmap
> mount aware), and it's not passed anywhere in fs/proc.
> 
> Looking at other uses of generic_fillattr, all of them use "init_user_ns":
> 

Interesting. It looks like this would have used mnt_userns from
vfs_getattr_nosec() before proc_fd_getattr() is wired up, right? I'm not
familiar enough with that change to say whether /proc should use one
value or the other, or perhaps it just doesn't matter.?

Christian?

Brian

> $ rg generic_fillattr fs/proc
> fs/proc/proc_net.c
> 301: generic_fillattr(&init_user_ns, inode, stat);
> 
> fs/proc/base.c
> 1970: generic_fillattr(&init_user_ns, inode, stat);
> 3856: generic_fillattr(&init_user_ns, inode, stat);
> 
> fs/proc/root.c
> 315: generic_fillattr(&init_user_ns, d_inode(path->dentry), stat);
> 
> fs/proc/generic.c
> 150: generic_fillattr(&init_user_ns, inode, stat);
> 
> fs/proc/proc_sysctl.c
> 841: generic_fillattr(&init_user_ns, inode, stat);
>