Re: [PATCH net-next v3 3/4] net: core: add getsockopt SO_PEERPIDFD

From: Aleksandr Mikhalitsyn
Date: Tue Apr 11 2023 - 12:03:08 EST

On Tue, Apr 11, 2023 at 5:57 PM Christian Brauner <brauner@xxxxxxxxxx> wrote:
>
> On Tue, Apr 11, 2023 at 12:42:30PM +0200, Alexander Mikhalitsyn wrote:
> > Add SO_PEERPIDFD which allows to get pidfd of peer socket holder pidfd.
> > This thing is direct analog of SO_PEERCRED which allows to get plain PID.
> >
> > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> > Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> > Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> > Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> > Cc: Leon Romanovsky <leon@xxxxxxxxxx>
> > Cc: David Ahern <dsahern@xxxxxxxxxx>
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> > Cc: Christian Brauner <brauner@xxxxxxxxxx>
> > Cc: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
> > Cc: Lennart Poettering <mzxreary@xxxxxxxxxxx>
> > Cc: Luca Boccassi <bluca@xxxxxxxxxx>
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Cc: netdev@xxxxxxxxxxxxxxx
> > Cc: linux-arch@xxxxxxxxxxxxxxx
> > Tested-by: Luca Boccassi <bluca@xxxxxxxxxx>
> > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
> > ---
> > v3:
> > - fixed possible fd leak (thanks to Christian Brauner)
> > v2:
> > According to review comments from Kuniyuki Iwashima and Christian Brauner:
> > - use pidfd_create(..) retval as a result
> > - whitespace change
> > ---
> > arch/alpha/include/uapi/asm/socket.h | 1 +
> > arch/mips/include/uapi/asm/socket.h | 1 +
> > arch/parisc/include/uapi/asm/socket.h | 1 +
> > arch/sparc/include/uapi/asm/socket.h | 1 +
> > include/uapi/asm-generic/socket.h | 1 +
> > net/core/sock.c | 33 +++++++++++++++++++++++++
> > net/socket.c | 7 ++++++
> > tools/include/uapi/asm-generic/socket.h | 1 +
> > 8 files changed, 46 insertions(+)
> >
> > diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
> > index ff310613ae64..e94f621903fe 100644
> > --- a/arch/alpha/include/uapi/asm/socket.h
> > +++ b/arch/alpha/include/uapi/asm/socket.h
> > @@ -138,6 +138,7 @@
> > #define SO_RCVMARK 75
> >
> > #define SO_PASSPIDFD 76
> > +#define SO_PEERPIDFD 77
> >
> > #if !defined(__KERNEL__)
> >
> > diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
> > index 762dcb80e4ec..60ebaed28a4c 100644
> > --- a/arch/mips/include/uapi/asm/socket.h
> > +++ b/arch/mips/include/uapi/asm/socket.h
> > @@ -149,6 +149,7 @@
> > #define SO_RCVMARK 75
> >
> > #define SO_PASSPIDFD 76
> > +#define SO_PEERPIDFD 77
> >
> > #if !defined(__KERNEL__)
> >
> > diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
> > index df16a3e16d64..be264c2b1a11 100644
> > --- a/arch/parisc/include/uapi/asm/socket.h
> > +++ b/arch/parisc/include/uapi/asm/socket.h
> > @@ -130,6 +130,7 @@
> > #define SO_RCVMARK 0x4049
> >
> > #define SO_PASSPIDFD 0x404A
> > +#define SO_PEERPIDFD 0x404B
> >
> > #if !defined(__KERNEL__)
> >
> > diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
> > index 6e2847804fea..682da3714686 100644
> > --- a/arch/sparc/include/uapi/asm/socket.h
> > +++ b/arch/sparc/include/uapi/asm/socket.h
> > @@ -131,6 +131,7 @@
> > #define SO_RCVMARK 0x0054
> >
> > #define SO_PASSPIDFD 0x0055
> > +#define SO_PEERPIDFD 0x0056
> >
> > #if !defined(__KERNEL__)
> >
> > diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
> > index b76169fdb80b..8ce8a39a1e5f 100644
> > --- a/include/uapi/asm-generic/socket.h
> > +++ b/include/uapi/asm-generic/socket.h
> > @@ -133,6 +133,7 @@
> > #define SO_RCVMARK 75
> >
> > #define SO_PASSPIDFD 76
> > +#define SO_PEERPIDFD 77
> >
> > #if !defined(__KERNEL__)
> >
> > diff --git a/net/core/sock.c b/net/core/sock.c
> > index 3f974246ba3e..2b040a69e355 100644
> > --- a/net/core/sock.c
> > +++ b/net/core/sock.c
> > @@ -1763,6 +1763,39 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
> > goto lenout;
> > }
> >
> > + case SO_PEERPIDFD:
> > + {
> > + struct pid *peer_pid;
> > + struct file *pidfd_file = NULL;
> > + int pidfd;
> > +
> > + if (len > sizeof(pidfd))
> > + len = sizeof(pidfd);
> > +
> > + spin_lock(&sk->sk_peer_lock);
> > + peer_pid = get_pid(sk->sk_peer_pid);
> > + spin_unlock(&sk->sk_peer_lock);
> > +
> > + pidfd = pidfd_prepare(peer_pid, 0, &pidfd_file);
> > +
> > + put_pid(peer_pid);
>
> Would be a bit nicer if this would be:
>
> pidfd = pidfd_prepare(peer_pid, 0, &pidfd_file);
> put_pid(peer_pid);
> if (pidfd < 0)
> return pidfd;
> if (copy_to_sockptr(optval, &pidfd, len) ||
> copy_to_sockptr(optlen, &len, sizeof(int)))
{
put_unused_fd(pidfd);
fput(pidfd_file);

are still needed there, right?

> return -EFAULT;
}

>
> fd_install(pidfd, pidfd_file);
> return 0;
>
> Otherwise seems good enough to me.

Will do.

>
> > +
> > + if (copy_to_sockptr(optval, &pidfd, len) ||
> > + copy_to_sockptr(optlen, &len, sizeof(int))) {
> > + if (pidfd >= 0) {
> > + put_unused_fd(pidfd);
> > + fput(pidfd_file);
> > + }
> > +
> > + return -EFAULT;
> > + }
> > +
> > + if (pidfd_file)
> > + fd_install(pidfd, pidfd_file);
> > +
> > + return 0;
> > + }
> > +
> > case SO_PEERGROUPS:
> > {
> > const struct cred *cred;
> > diff --git a/net/socket.c b/net/socket.c
> > index 9c1ef11de23f..505b85489354 100644
> > --- a/net/socket.c
> > +++ b/net/socket.c
> > @@ -2248,6 +2248,13 @@ static bool sockopt_installs_fd(int level, int optname)
> > default:
> > return false;
> > }
> > + } else if (level == SOL_SOCKET) {
> > + switch (optname) {
> > + case SO_PEERPIDFD:
> > + return true;
> > + default:
> > + return false;
> > + }
> > }
> >
> > return false;
> > diff --git a/tools/include/uapi/asm-generic/socket.h b/tools/include/uapi/asm-generic/socket.h
> > index fbbc4bf53ee3..54d9c8bf7c55 100644
> > --- a/tools/include/uapi/asm-generic/socket.h
> > +++ b/tools/include/uapi/asm-generic/socket.h
> > @@ -122,6 +122,7 @@
> > #define SO_RCVMARK 75
> >
> > #define SO_PASSPIDFD 76
> > +#define SO_PEERPIDFD 77
> >
> > #if !defined(__KERNEL__)
> >
> > --
> > 2.34.1
> >