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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: 09eed1192c ("neighbour: switch to standard rcu, instead of rcu_bh")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230510154646.370659-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2023-05-10 15:46:46 +00:00 committed by Jakub Kicinski
parent e93c9378e3
commit ef1148d448
2 changed files with 8 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
include/net/nexthop.h
View File

@ -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;

16
net/ipv6/ip6_fib.c
View File

@ -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 @@ iter_table:
}
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)