Message ID | 20170820003408.133176-1-tracywwnj@gmail.com |
---|---|
State | Changes Requested, archived |
Delegated to: | David Miller |
Headers | show |
On Sat, Aug 19, 2017 at 05:34:08PM -0700, Wei Wang wrote: > From: Wei Wang <weiwan@google.com> > > We currently keep rt->rt6i_node pointing to the fib6_node for the route. > And some functions make use of this pointer to dereference the fib6_node > from rt structure, e.g. rt6_check(). However, as there is neither > refcount nor rcu taken when dereferencing rt->rt6i_node, it could > potentially cause crashes as rt->rt6i_node could be set to NULL by other > CPUs when doing a route deletion. > This patch introduces an rcu grace period before freeing fib6_node and > makes sure the functions that dereference it takes rcu_read_lock(). > > Note: there is no "Fixes" tag because this bug was there in a very > early stage. > > Signed-off-by: Wei Wang <weiwan@google.com> > Acked-by: Eric Dumazet <edumazet@google.com> Acked-by: Martin KaFai Lau <kafai@fb.com> > --- > v2: removed one extra empty line > > include/net/ip6_fib.h | 30 +++++++++++++++++++++++++++++- > net/ipv6/ip6_fib.c | 20 ++++++++++++++++---- > net/ipv6/route.c | 14 +++++++++++--- > 3 files changed, 56 insertions(+), 8 deletions(-) > > diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h > index 71c1646298ae..977a86e3a8d9 100644 > --- a/include/net/ip6_fib.h > +++ b/include/net/ip6_fib.h > @@ -72,6 +72,7 @@ struct fib6_node { > __u16 fn_flags; > int fn_sernum; > struct rt6_info *rr_ptr; > + struct rcu_head rcu; > }; > > #ifndef CONFIG_IPV6_SUBTREES > @@ -171,13 +172,40 @@ static inline void rt6_update_expires(struct rt6_info *rt0, int timeout) > rt0->rt6i_flags |= RTF_EXPIRES; > } > > +/* Function to safely get fn->sernum for passed in rt > + * and store result in passed in cookie. > + * Return true if we can get cookie safely > + * Return false if not > + */ > +static inline bool rt6_get_cookie_safe(const struct rt6_info *rt, > + u32 *cookie) > +{ > + struct fib6_node *fn; > + bool status = false; > + > + rcu_read_lock(); > + fn = rcu_dereference(rt->rt6i_node); > + > + if (fn) { > + *cookie = fn->fn_sernum; > + status = true; > + } > + > + rcu_read_unlock(); > + return status; > +} > + > static inline u32 rt6_get_cookie(const struct rt6_info *rt) > { > + u32 cookie = 0; > + > if (rt->rt6i_flags & RTF_PCPU || > (unlikely(!list_empty(&rt->rt6i_uncached)) && rt->dst.from)) > rt = (struct rt6_info *)(rt->dst.from); > > - return rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0; > + rt6_get_cookie_safe(rt, &cookie); > + > + return cookie; > } > > static inline void ip6_rt_put(struct rt6_info *rt) > diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c > index 549aacc3cb2c..a9821c230e4e 100644 > --- a/net/ipv6/ip6_fib.c > +++ b/net/ipv6/ip6_fib.c > @@ -149,11 +149,23 @@ static struct fib6_node *node_alloc(void) > return fn; > } > > -static void node_free(struct fib6_node *fn) > +static void node_free_immediate(struct fib6_node *fn) > +{ > + kmem_cache_free(fib6_node_kmem, fn); > +} > + > +static void node_free_rcu(struct rcu_head *head) > { > + struct fib6_node *fn = container_of(head, struct fib6_node, rcu); > + > kmem_cache_free(fib6_node_kmem, fn); > } > > +static void node_free(struct fib6_node *fn) > +{ > + call_rcu(&fn->rcu, node_free_rcu); > +} > + > void rt6_free_pcpu(struct rt6_info *non_pcpu_rt) > { > int cpu; > @@ -697,9 +709,9 @@ static struct fib6_node *fib6_add_1(struct fib6_node *root, > > if (!in || !ln) { > if (in) > - node_free(in); > + node_free_immediate(in); > if (ln) > - node_free(ln); > + node_free_immediate(ln); > return ERR_PTR(-ENOMEM); > } > > @@ -1138,7 +1150,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, > root, and then (in failure) stale node > in main tree. > */ > - node_free(sfn); > + node_free_immediate(sfn); > err = PTR_ERR(sn); > goto failure; > } > diff --git a/net/ipv6/route.c b/net/ipv6/route.c > index bec12ae3e6b7..4de2d793c4b8 100644 > --- a/net/ipv6/route.c > +++ b/net/ipv6/route.c > @@ -1289,7 +1289,9 @@ static void rt6_dst_from_metrics_check(struct rt6_info *rt) > > static struct dst_entry *rt6_check(struct rt6_info *rt, u32 cookie) > { > - if (!rt->rt6i_node || (rt->rt6i_node->fn_sernum != cookie)) > + u32 rt_cookie; > + > + if (!rt6_get_cookie_safe(rt, &rt_cookie) || rt_cookie != cookie) > return NULL; > > if (rt6_check_expired(rt)) > @@ -1357,8 +1359,14 @@ static void ip6_link_failure(struct sk_buff *skb) > if (rt->rt6i_flags & RTF_CACHE) { > if (dst_hold_safe(&rt->dst)) > ip6_del_rt(rt); > - } else if (rt->rt6i_node && (rt->rt6i_flags & RTF_DEFAULT)) { > - rt->rt6i_node->fn_sernum = -1; > + } else { > + struct fib6_node *fn; > + > + rcu_read_lock(); > + fn = rcu_dereference(rt->rt6i_node); > + if (fn && (rt->rt6i_flags & RTF_DEFAULT)) > + fn->fn_sernum = -1; > + rcu_read_unlock(); > } > } > } > -- > 2.14.1.480.gb18f417b89-goog >
From: Wei Wang <weiwan@google.com> Date: Sat, 19 Aug 2017 17:34:08 -0700 > From: Wei Wang <weiwan@google.com> > > We currently keep rt->rt6i_node pointing to the fib6_node for the route. > And some functions make use of this pointer to dereference the fib6_node > from rt structure, e.g. rt6_check(). However, as there is neither > refcount nor rcu taken when dereferencing rt->rt6i_node, it could > potentially cause crashes as rt->rt6i_node could be set to NULL by other > CPUs when doing a route deletion. > This patch introduces an rcu grace period before freeing fib6_node and > makes sure the functions that dereference it takes rcu_read_lock(). > > Note: there is no "Fixes" tag because this bug was there in a very > early stage. > > Signed-off-by: Wei Wang <weiwan@google.com> > Acked-by: Eric Dumazet <edumazet@google.com> > --- > v2: removed one extra empty line Goodness.... where to start. If this bug has been around forever, why did you make this patch against net-next instead of net? (I can tell just by looking at the patch because rt6_free_pcpu() is static in 'net' yet it is not static in the diff hunk which matches net-next) And if you made it against net-next, why are you saying "net" in your subject line instead of "[PATCH net-next v2]"? Please sort this out properly, and resubmit. Thank you.
> Goodness.... where to start. > > If this bug has been around forever, why did you make this patch > against net-next instead of net? (I can tell just by looking at > the patch because rt6_free_pcpu() is static in 'net' yet it is > not static in the diff hunk which matches net-next) > > And if you made it against net-next, why are you saying "net" in > your subject line instead of "[PATCH net-next v2]"? > > Please sort this out properly, and resubmit. > > Thank you. It should be applied to "net". I will rebase my change and resubmit. Sorry for the confusion. Thanks. Wei On Sun, Aug 20, 2017 at 7:59 PM, David Miller <davem@davemloft.net> wrote: > From: Wei Wang <weiwan@google.com> > Date: Sat, 19 Aug 2017 17:34:08 -0700 > >> From: Wei Wang <weiwan@google.com> >> >> We currently keep rt->rt6i_node pointing to the fib6_node for the route. >> And some functions make use of this pointer to dereference the fib6_node >> from rt structure, e.g. rt6_check(). However, as there is neither >> refcount nor rcu taken when dereferencing rt->rt6i_node, it could >> potentially cause crashes as rt->rt6i_node could be set to NULL by other >> CPUs when doing a route deletion. >> This patch introduces an rcu grace period before freeing fib6_node and >> makes sure the functions that dereference it takes rcu_read_lock(). >> >> Note: there is no "Fixes" tag because this bug was there in a very >> early stage. >> >> Signed-off-by: Wei Wang <weiwan@google.com> >> Acked-by: Eric Dumazet <edumazet@google.com> >> --- >> v2: removed one extra empty line > > Goodness.... where to start. > > If this bug has been around forever, why did you make this patch > against net-next instead of net? (I can tell just by looking at > the patch because rt6_free_pcpu() is static in 'net' yet it is > not static in the diff hunk which matches net-next) > > And if you made it against net-next, why are you saying "net" in > your subject line instead of "[PATCH net-next v2]"? > > Please sort this out properly, and resubmit. > > Thank you.
diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h index 71c1646298ae..977a86e3a8d9 100644 --- a/include/net/ip6_fib.h +++ b/include/net/ip6_fib.h @@ -72,6 +72,7 @@ struct fib6_node { __u16 fn_flags; int fn_sernum; struct rt6_info *rr_ptr; + struct rcu_head rcu; }; #ifndef CONFIG_IPV6_SUBTREES @@ -171,13 +172,40 @@ static inline void rt6_update_expires(struct rt6_info *rt0, int timeout) rt0->rt6i_flags |= RTF_EXPIRES; } +/* Function to safely get fn->sernum for passed in rt + * and store result in passed in cookie. + * Return true if we can get cookie safely + * Return false if not + */ +static inline bool rt6_get_cookie_safe(const struct rt6_info *rt, + u32 *cookie) +{ + struct fib6_node *fn; + bool status = false; + + rcu_read_lock(); + fn = rcu_dereference(rt->rt6i_node); + + if (fn) { + *cookie = fn->fn_sernum; + status = true; + } + + rcu_read_unlock(); + return status; +} + static inline u32 rt6_get_cookie(const struct rt6_info *rt) { + u32 cookie = 0; + if (rt->rt6i_flags & RTF_PCPU || (unlikely(!list_empty(&rt->rt6i_uncached)) && rt->dst.from)) rt = (struct rt6_info *)(rt->dst.from); - return rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0; + rt6_get_cookie_safe(rt, &cookie); + + return cookie; } static inline void ip6_rt_put(struct rt6_info *rt) diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index 549aacc3cb2c..a9821c230e4e 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -149,11 +149,23 @@ static struct fib6_node *node_alloc(void) return fn; } -static void node_free(struct fib6_node *fn) +static void node_free_immediate(struct fib6_node *fn) +{ + kmem_cache_free(fib6_node_kmem, fn); +} + +static void node_free_rcu(struct rcu_head *head) { + struct fib6_node *fn = container_of(head, struct fib6_node, rcu); + kmem_cache_free(fib6_node_kmem, fn); } +static void node_free(struct fib6_node *fn) +{ + call_rcu(&fn->rcu, node_free_rcu); +} + void rt6_free_pcpu(struct rt6_info *non_pcpu_rt) { int cpu; @@ -697,9 +709,9 @@ static struct fib6_node *fib6_add_1(struct fib6_node *root, if (!in || !ln) { if (in) - node_free(in); + node_free_immediate(in); if (ln) - node_free(ln); + node_free_immediate(ln); return ERR_PTR(-ENOMEM); } @@ -1138,7 +1150,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, root, and then (in failure) stale node in main tree. */ - node_free(sfn); + node_free_immediate(sfn); err = PTR_ERR(sn); goto failure; } diff --git a/net/ipv6/route.c b/net/ipv6/route.c index bec12ae3e6b7..4de2d793c4b8 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1289,7 +1289,9 @@ static void rt6_dst_from_metrics_check(struct rt6_info *rt) static struct dst_entry *rt6_check(struct rt6_info *rt, u32 cookie) { - if (!rt->rt6i_node || (rt->rt6i_node->fn_sernum != cookie)) + u32 rt_cookie; + + if (!rt6_get_cookie_safe(rt, &rt_cookie) || rt_cookie != cookie) return NULL; if (rt6_check_expired(rt)) @@ -1357,8 +1359,14 @@ static void ip6_link_failure(struct sk_buff *skb) if (rt->rt6i_flags & RTF_CACHE) { if (dst_hold_safe(&rt->dst)) ip6_del_rt(rt); - } else if (rt->rt6i_node && (rt->rt6i_flags & RTF_DEFAULT)) { - rt->rt6i_node->fn_sernum = -1; + } else { + struct fib6_node *fn; + + rcu_read_lock(); + fn = rcu_dereference(rt->rt6i_node); + if (fn && (rt->rt6i_flags & RTF_DEFAULT)) + fn->fn_sernum = -1; + rcu_read_unlock(); } } }