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Message-ID: <CANn89iJaykUZ0iOCB+-6CzFk0fNHpHUjLLOUx6sgQkLj7=NZLQ@mail.gmail.com>
Date: Fri, 23 Feb 2024 12:51:43 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Jiri Pirko <jiri@...dia.com>, Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Subject: Re: [PATCH net] dpll: rely on rcu for netdev_dpll_pin()
On Fri, Feb 23, 2024 at 10:00 AM Jiri Pirko <jiri@...nulli.us> wrote:
>
> Thu, Feb 22, 2024 at 05:48:51PM CET, edumazet@...gle.com wrote:
> >This fixes a possible UAF in if_nlmsg_size(),
> >which can run without RTNL.
> >
> >Add rcu protection to "struct dpll_pin"
> >
> >Note: This looks possible to no longer acquire RTNL in
> >netdev_dpll_pin_assign().
>
> Yeah, looks like no longer needed. Will you do a follow-up for net-next
> once this is applied to -net?
Absolutely, this came while I was working on my RTNL->RCU conversion
of "ip l" in net-next.
>
>
> >
> >Fixes: 5f1842692880 ("netdev: expose DPLL pin handle for netdevice")
> >Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> >Cc: Jiri Pirko <jiri@...dia.com>
> >Cc: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
> >Cc: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
> >---
> > drivers/dpll/dpll_core.c | 2 +-
> > drivers/dpll/dpll_core.h | 2 ++
> > include/linux/dpll.h | 11 +++++++++++
> > include/linux/netdevice.h | 11 +----------
> > net/core/dev.c | 2 +-
> > net/core/rtnetlink.c | 2 ++
> > 6 files changed, 18 insertions(+), 12 deletions(-)
> >
> >diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
> >index 5152bd1b0daf599869195e81805fbb2709dbe6b4..4c2bb27c99fe4e517b0d92c4ae3db83a679c7d11 100644
> >--- a/drivers/dpll/dpll_core.c
> >+++ b/drivers/dpll/dpll_core.c
> >@@ -564,7 +564,7 @@ void dpll_pin_put(struct dpll_pin *pin)
> > xa_destroy(&pin->parent_refs);
> > xa_erase(&dpll_pin_xa, pin->id);
> > dpll_pin_prop_free(&pin->prop);
> >- kfree(pin);
> >+ kfree_rcu(pin, rcu);
> > }
> > mutex_unlock(&dpll_lock);
> > }
> >diff --git a/drivers/dpll/dpll_core.h b/drivers/dpll/dpll_core.h
> >index 717f715015c742238d5585fddc5cd267fbb0db9f..2b6d8ef1cdf36cff24328e497c49d667659dd0e6 100644
> >--- a/drivers/dpll/dpll_core.h
> >+++ b/drivers/dpll/dpll_core.h
> >@@ -47,6 +47,7 @@ struct dpll_device {
> > * @prop: pin properties copied from the registerer
> > * @rclk_dev_name: holds name of device when pin can recover clock from it
> > * @refcount: refcount
> >+ * @rcu: rcu_head for kfree_rcu()
> > **/
> > struct dpll_pin {
> > u32 id;
> >@@ -57,6 +58,7 @@ struct dpll_pin {
> > struct xarray parent_refs;
> > struct dpll_pin_properties prop;
> > refcount_t refcount;
> >+ struct rcu_head rcu;
> > };
> >
> > /**
> >diff --git a/include/linux/dpll.h b/include/linux/dpll.h
> >index 9cf896ea1d4122f3bc7094e46a5af81b999937dc..4ec2fe9caf5a3f284afd0cfe4fc7c2bf42cbbc60 100644
> >--- a/include/linux/dpll.h
> >+++ b/include/linux/dpll.h
> >@@ -10,6 +10,8 @@
> > #include <uapi/linux/dpll.h>
> > #include <linux/device.h>
> > #include <linux/netlink.h>
> >+#include <linux/netdevice.h>
> >+#include <linux/rtnetlink.h>
> >
> > struct dpll_device;
> > struct dpll_pin;
> >@@ -167,4 +169,13 @@ int dpll_device_change_ntf(struct dpll_device *dpll);
> >
> > int dpll_pin_change_ntf(struct dpll_pin *pin);
> >
> >+static inline struct dpll_pin *netdev_dpll_pin(const struct net_device *dev)
> >+{
> >+#if IS_ENABLED(CONFIG_DPLL)
> >+ return rcu_dereference_rtnl(dev->dpll_pin);
> >+#else
> >+ return NULL;
> >+#endif
>
> Why you moved netdev_dpll_pin() here?
Because of the rcu_dereference_rtnl() call, not available to
include/linux/netdevice.h
Adding the missing include would have been more painful.
include/linux/netdevice.h being included everywhere and being bloated already,
I think moving netdev_dpll_pin() helper in dpll.h is better (should
not increase compile time for the kernel)
>
>
> >+}
> >+
> > #endif
> >diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> >index ef7bfbb9849733fa7f1f097ba53a36a68cc3384b..a9c973b92294bb110cf3cd336485972127b01b58 100644
> >--- a/include/linux/netdevice.h
> >+++ b/include/linux/netdevice.h
> >@@ -2469,7 +2469,7 @@ struct net_device {
> > struct devlink_port *devlink_port;
> >
> > #if IS_ENABLED(CONFIG_DPLL)
> >- struct dpll_pin *dpll_pin;
> >+ struct dpll_pin __rcu *dpll_pin;
> > #endif
> > #if IS_ENABLED(CONFIG_PAGE_POOL)
> > /** @page_pools: page pools created for this netdevice */
> >@@ -4035,15 +4035,6 @@ bool netdev_port_same_parent_id(struct net_device *a, struct net_device *b);
> > void netdev_dpll_pin_set(struct net_device *dev, struct dpll_pin *dpll_pin);
> > void netdev_dpll_pin_clear(struct net_device *dev);
> >
> >-static inline struct dpll_pin *netdev_dpll_pin(const struct net_device *dev)
> >-{
> >-#if IS_ENABLED(CONFIG_DPLL)
> >- return dev->dpll_pin;
> >-#else
> >- return NULL;
> >-#endif
> >-}
> >-
> > struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *dev, bool *again);
> > struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
> > struct netdev_queue *txq, int *ret);
> >diff --git a/net/core/dev.c b/net/core/dev.c
> >index 73a0219730075e666c4f11f668a50dbf9f9afa97..0230391c78f71e22d3c0e925ff8d3d792aa54a32 100644
> >--- a/net/core/dev.c
> >+++ b/net/core/dev.c
> >@@ -9078,7 +9078,7 @@ static void netdev_dpll_pin_assign(struct net_device *dev, struct dpll_pin *dpll
> > {
> > #if IS_ENABLED(CONFIG_DPLL)
> > rtnl_lock();
> >- dev->dpll_pin = dpll_pin;
> >+ rcu_assign_pointer(dev->dpll_pin, dpll_pin);
> > rtnl_unlock();
> > #endif
> > }
> >diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> >index 9c4f427f3a5057b52ec05405e8b15b8ca2246b4b..6239aa62a29cb8752a53e3f75a48a1e2fdd3b0ec 100644
> >--- a/net/core/rtnetlink.c
> >+++ b/net/core/rtnetlink.c
> >@@ -1057,7 +1057,9 @@ static size_t rtnl_dpll_pin_size(const struct net_device *dev)
> > {
> > size_t size = nla_total_size(0); /* nest IFLA_DPLL_PIN */
> >
> >+ rcu_read_lock();
>
> Why do you need to take the rcu read lock here? Isn't this called
> with either rtnl held of rcu read lock held?
>
> And if you need to take rcu read lock here, why you use
> rcu_dereference_rtnl() instead of rcu_dereference() in
> netdev_dpll_pin()?
This is because I discovered the issue while working on net-next tree,
and basically had to fix the bug in net tree, I had to prune my WIP to
get to the fix.
You are right, the rcu_read_lock() is not really needed here.
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