| Message ID | 20250317-rpc-shutdown-v1-9-85ba8e20b75d@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | nfs/sunrpc: stop holding netns references in client-side NFS and RPC objects | expand |
On Mon, 2025-03-17 at 17:00 -0400, Jeff Layton wrote: > With the move to having sunrpc client xprts not hold active > references > to the net namespace, there is no need to upgrade the socket's > reference > in xs_create_sock. Just keep the passive reference instead. > > Signed-off-by: Jeff Layton <jlayton@kernel.org> > --- > net/sunrpc/xprtsock.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c > index > 83cc095846d356f24aed26e2f98525662a6cff1f..0c3d7552f772d6f8477a3aed8f0 > c513b62cdf589 100644 > --- a/net/sunrpc/xprtsock.c > +++ b/net/sunrpc/xprtsock.c > @@ -1941,9 +1941,6 @@ static struct socket *xs_create_sock(struct > rpc_xprt *xprt, > goto out; > } > > - if (protocol == IPPROTO_TCP) > - sk_net_refcnt_upgrade(sock->sk); > - > filp = sock_alloc_file(sock, O_NONBLOCK, NULL); > if (IS_ERR(filp)) > return ERR_CAST(filp); > Is this not going to reintroduce the bug described by https://lore.kernel.org/netdev/67b72aeb.050a0220.14d86d.0283.GAE@google.com/T/#u ? As I understand it, the problem has nothing to do with whether or not NFS or the RPC layer holds a reference to the net namespace, but rather whether there are still packets in the socket queues at the time when that net namespace is being freed.
On Mon, 2025-03-17 at 21:28 +0000, Trond Myklebust wrote: > On Mon, 2025-03-17 at 17:00 -0400, Jeff Layton wrote: > > With the move to having sunrpc client xprts not hold active > > references > > to the net namespace, there is no need to upgrade the socket's > > reference > > in xs_create_sock. Just keep the passive reference instead. > > > > Signed-off-by: Jeff Layton <jlayton@kernel.org> > > --- > > net/sunrpc/xprtsock.c | 3 --- > > 1 file changed, 3 deletions(-) > > > > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c > > index > > 83cc095846d356f24aed26e2f98525662a6cff1f..0c3d7552f772d6f8477a3aed8f0 > > c513b62cdf589 100644 > > --- a/net/sunrpc/xprtsock.c > > +++ b/net/sunrpc/xprtsock.c > > @@ -1941,9 +1941,6 @@ static struct socket *xs_create_sock(struct > > rpc_xprt *xprt, > > goto out; > > } > > > > - if (protocol == IPPROTO_TCP) > > - sk_net_refcnt_upgrade(sock->sk); > > - > > filp = sock_alloc_file(sock, O_NONBLOCK, NULL); > > if (IS_ERR(filp)) > > return ERR_CAST(filp); > > > > Is this not going to reintroduce the bug described by > https://lore.kernel.org/netdev/67b72aeb.050a0220.14d86d.0283.GAE@google.com/T/#u > ? > > As I understand it, the problem has nothing to do with whether or not > NFS or the RPC layer holds a reference to the net namespace, but rather > whether there are still packets in the socket queues at the time when > that net namespace is being freed. > > I don't think so. That syzkaller report was closed by this patch: 5c70eb5c593d net: better track kernel sockets lifetime That says: "To fix this, make sure that kernel sockets own a reference on net passive." With this, we still do keep a passive reference on the net in the socket, which I think is enough. That said, I'd appreciate a look at this from the netdev folks.
On Mon, 2025-03-17 at 17:36 -0400, Jeff Layton wrote: > On Mon, 2025-03-17 at 21:28 +0000, Trond Myklebust wrote: > > On Mon, 2025-03-17 at 17:00 -0400, Jeff Layton wrote: > > > With the move to having sunrpc client xprts not hold active > > > references > > > to the net namespace, there is no need to upgrade the socket's > > > reference > > > in xs_create_sock. Just keep the passive reference instead. > > > > > > Signed-off-by: Jeff Layton <jlayton@kernel.org> > > > --- > > > net/sunrpc/xprtsock.c | 3 --- > > > 1 file changed, 3 deletions(-) > > > > > > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c > > > index > > > 83cc095846d356f24aed26e2f98525662a6cff1f..0c3d7552f772d6f8477a3ae > > > d8f0 > > > c513b62cdf589 100644 > > > --- a/net/sunrpc/xprtsock.c > > > +++ b/net/sunrpc/xprtsock.c > > > @@ -1941,9 +1941,6 @@ static struct socket *xs_create_sock(struct > > > rpc_xprt *xprt, > > > goto out; > > > } > > > > > > - if (protocol == IPPROTO_TCP) > > > - sk_net_refcnt_upgrade(sock->sk); > > > - > > > filp = sock_alloc_file(sock, O_NONBLOCK, NULL); > > > if (IS_ERR(filp)) > > > return ERR_CAST(filp); > > > > > > > Is this not going to reintroduce the bug described by > > https://lore.kernel.org/netdev/67b72aeb.050a0220.14d86d.0283.GAE@google.com/T/#u > > ? > > > > As I understand it, the problem has nothing to do with whether or > > not > > NFS or the RPC layer holds a reference to the net namespace, but > > rather > > whether there are still packets in the socket queues at the time > > when > > that net namespace is being freed. > > > > > > I don't think so. That syzkaller report was closed by this patch: > > 5c70eb5c593d net: better track kernel sockets lifetime > > That says: > > "To fix this, make sure that kernel sockets own a reference on > net > passive." > > With this, we still do keep a passive reference on the net in the > socket, which I think is enough. No. You just removed that by reverting the patch that assigns the passive reference. > > That said, I'd appreciate a look at this from the netdev folks.
On Mon, 2025-03-17 at 21:37 +0000, Trond Myklebust wrote: > On Mon, 2025-03-17 at 17:36 -0400, Jeff Layton wrote: > > On Mon, 2025-03-17 at 21:28 +0000, Trond Myklebust wrote: > > > On Mon, 2025-03-17 at 17:00 -0400, Jeff Layton wrote: > > > > With the move to having sunrpc client xprts not hold active > > > > references > > > > to the net namespace, there is no need to upgrade the socket's > > > > reference > > > > in xs_create_sock. Just keep the passive reference instead. > > > > > > > > Signed-off-by: Jeff Layton <jlayton@kernel.org> > > > > --- > > > > net/sunrpc/xprtsock.c | 3 --- > > > > 1 file changed, 3 deletions(-) > > > > > > > > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c > > > > index > > > > 83cc095846d356f24aed26e2f98525662a6cff1f..0c3d7552f772d6f8477a3ae > > > > d8f0 > > > > c513b62cdf589 100644 > > > > --- a/net/sunrpc/xprtsock.c > > > > +++ b/net/sunrpc/xprtsock.c > > > > @@ -1941,9 +1941,6 @@ static struct socket *xs_create_sock(struct > > > > rpc_xprt *xprt, > > > > goto out; > > > > } > > > > > > > > - if (protocol == IPPROTO_TCP) > > > > - sk_net_refcnt_upgrade(sock->sk); > > > > - > > > > filp = sock_alloc_file(sock, O_NONBLOCK, NULL); > > > > if (IS_ERR(filp)) > > > > return ERR_CAST(filp); > > > > > > > > > > Is this not going to reintroduce the bug described by > > > https://lore.kernel.org/netdev/67b72aeb.050a0220.14d86d.0283.GAE@google.com/T/#u > > > ? > > > > > > As I understand it, the problem has nothing to do with whether or > > > not > > > NFS or the RPC layer holds a reference to the net namespace, but > > > rather > > > whether there are still packets in the socket queues at the time > > > when > > > that net namespace is being freed. > > > > > > > > > > I don't think so. That syzkaller report was closed by this patch: > > > > 5c70eb5c593d net: better track kernel sockets lifetime > > > > That says: > > > > "To fix this, make sure that kernel sockets own a reference on > > net > > passive." > > > > With this, we still do keep a passive reference on the net in the > > socket, which I think is enough. > > No. You just removed that by reverting the patch that assigns the > passive reference. > That's not how I read sk_net_refcnt_upgrade(). The socket already holds a passive reference on the netns. sk_net_refcnt_upgrade() puts that reference and then gets an active reference to the netns. With this patchset, we just need to keep the passive one (I think).
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index 83cc095846d356f24aed26e2f98525662a6cff1f..0c3d7552f772d6f8477a3aed8f0c513b62cdf589 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -1941,9 +1941,6 @@ static struct socket *xs_create_sock(struct rpc_xprt *xprt, goto out; } - if (protocol == IPPROTO_TCP) - sk_net_refcnt_upgrade(sock->sk); - filp = sock_alloc_file(sock, O_NONBLOCK, NULL); if (IS_ERR(filp)) return ERR_CAST(filp);
With the move to having sunrpc client xprts not hold active references to the net namespace, there is no need to upgrade the socket's reference in xs_create_sock. Just keep the passive reference instead. Signed-off-by: Jeff Layton <jlayton@kernel.org> --- net/sunrpc/xprtsock.c | 3 --- 1 file changed, 3 deletions(-)