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Date: Wed, 10 May 2023 15:46:46 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, syzbot <syzkaller@...glegroups.com>
Subject: [PATCH net] ipv6: remove nexthop_fib6_nh_bh()
After blamed commit, nexthop_fib6_nh_bh() and nexthop_fib6_nh()
are the same.
Delete nexthop_fib6_nh_bh(), and convert /proc/net/ipv6_route
to standard rcu to avoid this splat:
[ 5723.180080] WARNING: suspicious RCU usage
[ 5723.180083] -----------------------------
[ 5723.180084] include/net/nexthop.h:516 suspicious rcu_dereference_check() usage!
[ 5723.180086]
other info that might help us debug this:
[ 5723.180087]
rcu_scheduler_active = 2, debug_locks = 1
[ 5723.180089] 2 locks held by cat/55856:
[ 5723.180091] #0: ffff9440a582afa8 (&p->lock){+.+.}-{3:3}, at: seq_read_iter (fs/seq_file.c:188)
[ 5723.180100] #1: ffffffffaac07040 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire (include/linux/rcupdate.h:326)
[ 5723.180109]
stack backtrace:
[ 5723.180111] CPU: 14 PID: 55856 Comm: cat Tainted: G S I 6.3.0-dbx-DEV #528
[ 5723.180115] Call Trace:
[ 5723.180117] <TASK>
[ 5723.180119] dump_stack_lvl (lib/dump_stack.c:107)
[ 5723.180124] dump_stack (lib/dump_stack.c:114)
[ 5723.180126] lockdep_rcu_suspicious (include/linux/context_tracking.h:122)
[ 5723.180132] ipv6_route_seq_show (include/net/nexthop.h:?)
[ 5723.180135] ? ipv6_route_seq_next (net/ipv6/ip6_fib.c:2605)
[ 5723.180140] seq_read_iter (fs/seq_file.c:272)
[ 5723.180145] seq_read (fs/seq_file.c:163)
[ 5723.180151] proc_reg_read (fs/proc/inode.c:316 fs/proc/inode.c:328)
[ 5723.180155] vfs_read (fs/read_write.c:468)
[ 5723.180160] ? up_read (kernel/locking/rwsem.c:1617)
[ 5723.180164] ksys_read (fs/read_write.c:613)
[ 5723.180168] __x64_sys_read (fs/read_write.c:621)
[ 5723.180170] do_syscall_64 (arch/x86/entry/common.c:?)
[ 5723.180174] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)
[ 5723.180177] RIP: 0033:0x7fa455677d2a
Fixes: 09eed1192cec ("neighbour: switch to standard rcu, instead of rcu_bh")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/net/nexthop.h | 23 -----------------------
net/ipv6/ip6_fib.c | 16 ++++++++--------
2 files changed, 8 insertions(+), 31 deletions(-)
diff --git a/include/net/nexthop.h b/include/net/nexthop.h
index 9fa291a046211e4fc1c7ae56094a124c4ce0a516..2b12725de9c094f6ac89831576a2556d5dad5e64 100644
--- a/include/net/nexthop.h
+++ b/include/net/nexthop.h
@@ -497,29 +497,6 @@ static inline struct fib6_nh *nexthop_fib6_nh(struct nexthop *nh)
return NULL;
}
-/* Variant of nexthop_fib6_nh().
- * Caller should either hold rcu_read_lock(), or RTNL.
- */
-static inline struct fib6_nh *nexthop_fib6_nh_bh(struct nexthop *nh)
-{
- struct nh_info *nhi;
-
- if (nh->is_group) {
- struct nh_group *nh_grp;
-
- nh_grp = rcu_dereference_rtnl(nh->nh_grp);
- nh = nexthop_mpath_select(nh_grp, 0);
- if (!nh)
- return NULL;
- }
-
- nhi = rcu_dereference_rtnl(nh->nh_info);
- if (nhi->family == AF_INET6)
- return &nhi->fib6_nh;
-
- return NULL;
-}
-
static inline struct net_device *fib6_info_nh_dev(struct fib6_info *f6i)
{
struct fib6_nh *fib6_nh;
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 2438da5ff6da810d9f612fc66df4d28510f50f10..bac768d36cc19fbaa2ac80be42c15388180bacb3 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -2491,7 +2491,7 @@ static int ipv6_route_native_seq_show(struct seq_file *seq, void *v)
const struct net_device *dev;
if (rt->nh)
- fib6_nh = nexthop_fib6_nh_bh(rt->nh);
+ fib6_nh = nexthop_fib6_nh(rt->nh);
seq_printf(seq, "%pi6 %02x ", &rt->fib6_dst.addr, rt->fib6_dst.plen);
@@ -2556,14 +2556,14 @@ static struct fib6_table *ipv6_route_seq_next_table(struct fib6_table *tbl,
if (tbl) {
h = (tbl->tb6_id & (FIB6_TABLE_HASHSZ - 1)) + 1;
- node = rcu_dereference_bh(hlist_next_rcu(&tbl->tb6_hlist));
+ node = rcu_dereference(hlist_next_rcu(&tbl->tb6_hlist));
} else {
h = 0;
node = NULL;
}
while (!node && h < FIB6_TABLE_HASHSZ) {
- node = rcu_dereference_bh(
+ node = rcu_dereference(
hlist_first_rcu(&net->ipv6.fib_table_hash[h++]));
}
return hlist_entry_safe(node, struct fib6_table, tb6_hlist);
@@ -2593,7 +2593,7 @@ static void *ipv6_route_seq_next(struct seq_file *seq, void *v, loff_t *pos)
if (!v)
goto iter_table;
- n = rcu_dereference_bh(((struct fib6_info *)v)->fib6_next);
+ n = rcu_dereference(((struct fib6_info *)v)->fib6_next);
if (n)
return n;
@@ -2619,12 +2619,12 @@ static void *ipv6_route_seq_next(struct seq_file *seq, void *v, loff_t *pos)
}
static void *ipv6_route_seq_start(struct seq_file *seq, loff_t *pos)
- __acquires(RCU_BH)
+ __acquires(RCU)
{
struct net *net = seq_file_net(seq);
struct ipv6_route_iter *iter = seq->private;
- rcu_read_lock_bh();
+ rcu_read_lock();
iter->tbl = ipv6_route_seq_next_table(NULL, net);
iter->skip = *pos;
@@ -2645,7 +2645,7 @@ static bool ipv6_route_iter_active(struct ipv6_route_iter *iter)
}
static void ipv6_route_native_seq_stop(struct seq_file *seq, void *v)
- __releases(RCU_BH)
+ __releases(RCU)
{
struct net *net = seq_file_net(seq);
struct ipv6_route_iter *iter = seq->private;
@@ -2653,7 +2653,7 @@ static void ipv6_route_native_seq_stop(struct seq_file *seq, void *v)
if (ipv6_route_iter_active(iter))
fib6_walker_unlink(net, &iter->w);
- rcu_read_unlock_bh();
+ rcu_read_unlock();
}
#if IS_BUILTIN(CONFIG_IPV6) && defined(CONFIG_BPF_SYSCALL)
--
2.40.1.521.gf1e218fcd8-goog
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