[PATCH 4.19 37/86] ipv6: annotate accesses to fn->fn_sernum

Greg Kroah-Hartman
2022-02-07T11:25:10Z

From: Eric Dumazet <edumazet@google.com>

commit aafc2e3285c2d7a79b7ee15221c19fbeca7b1509 upstream.

struct fib6_node's fn_sernum field can be
read while other threads change it.

Add READ_ONCE()/WRITE_ONCE() annotations.

Do not change existing smp barriers in fib6_get_cookie_safe()
and __fib6_update_sernum_upto_root()

syzbot reported:

BUG: KCSAN: data-race in fib6_clean_node / inet6_csk_route_socket

write to 0xffff88813df62e2c of 4 bytes by task 1920 on cpu 1:
fib6_clean_node+0xc2/0x260 net/ipv6/ip6_fib.c:2178
fib6_walk_continue+0x38e/0x430 net/ipv6/ip6_fib.c:2112
fib6_walk net/ipv6/ip6_fib.c:2160 [inline]
fib6_clean_tree net/ipv6/ip6_fib.c:2240 [inline]
__fib6_clean_all+0x1a9/0x2e0 net/ipv6/ip6_fib.c:2256
fib6_flush_trees+0x6c/0x80 net/ipv6/ip6_fib.c:2281
rt_genid_bump_ipv6 include/net/net_namespace.h:488 [inline]
addrconf_dad_completed+0x57f/0x870 net/ipv6/addrconf.c:4230
addrconf_dad_work+0x908/0x1170
process_one_work+0x3f6/0x960 kernel/workqueue.c:2307
worker_thread+0x616/0xa70 kernel/workqueue.c:2454
kthread+0x1bf/0x1e0 kernel/kthread.c:359
ret_from_fork+0x1f/0x30

read to 0xffff88813df62e2c of 4 bytes by task 15701 on cpu 0:
fib6_get_cookie_safe include/net/ip6_fib.h:285 [inline]
rt6_get_cookie include/net/ip6_fib.h:306 [inline]
ip6_dst_store include/net/ip6_route.h:234 [inline]
inet6_csk_route_socket+0x352/0x3c0 net/ipv6/inet6_connection_sock.c:109
inet6_csk_xmit+0x91/0x1e0 net/ipv6/inet6_connection_sock.c:121
__tcp_transmit_skb+0x1323/0x1840 net/ipv4/tcp_output.c:1402
tcp_transmit_skb net/ipv4/tcp_output.c:1420 [inline]
tcp_write_xmit+0x1450/0x4460 net/ipv4/tcp_output.c:2680
__tcp_push_pending_frames+0x68/0x1c0 net/ipv4/tcp_output.c:2864
tcp_push+0x2d9/0x2f0 net/ipv4/tcp.c:725
mptcp_push_release net/mptcp/protocol.c:1491 [inline]
__mptcp_push_pending+0x46c/0x490 net/mptcp/protocol.c:1578
mptcp_sendmsg+0x9ec/0xa50 net/mptcp/protocol.c:1764
inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:643
sock_sendmsg_nosec net/socket.c:705 [inline]
sock_sendmsg net/socket.c:725 [inline]
kernel_sendmsg+0x97/0xd0 net/socket.c:745
sock_no_sendpage+0x84/0xb0 net/core/sock.c:3086
inet_sendpage+0x9d/0xc0 net/ipv4/af_inet.c:834
kernel_sendpage+0x187/0x200 net/socket.c:3492
sock_sendpage+0x5a/0x70 net/socket.c:1007
pipe_to_sendpage+0x128/0x160 fs/splice.c:364
splice_from_pipe_feed fs/splice.c:418 [inline]
__splice_from_pipe+0x207/0x500 fs/splice.c:562
splice_from_pipe fs/splice.c:597 [inline]
generic_splice_sendpage+0x94/0xd0 fs/splice.c:746
do_splice_from fs/splice.c:767 [inline]
direct_splice_actor+0x80/0xa0 fs/splice.c:936
splice_direct_to_actor+0x345/0x650 fs/splice.c:891
do_splice_direct+0x106/0x190 fs/splice.c:979
do_sendfile+0x675/0xc40 fs/read_write.c:1245
__do_sys_sendfile64 fs/read_write.c:1310 [inline]
__se_sys_sendfile64 fs/read_write.c:1296 [inline]
__x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1296
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000026f -> 0x00000271

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 15701 Comm: syz-executor.2 Not tainted 5.16.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

The Fixes tag I chose is probably arbitrary, I do not think
we need to backport this patch to older kernels.

Fixes: c5cff8561d2d ("ipv6: add rcu grace period before freeing fib6_node")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Link: https://lore.kernel.org/r/20220120174112.1126644-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/ip6_fib.h | 2 +-
net/ipv6/ip6_fib.c | 23 +++++++++++++----------
net/ipv6/route.c | 2 +-
3 files changed, 15 insertions(+), 12 deletions(-)

--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -243,7 +243,7 @@ static inline bool fib6_get_cookie_safe(
fn = rcu_dereference(f6i->fib6_node);

if (fn) {
- *cookie = fn->fn_sernum;
+ *cookie = READ_ONCE(fn->fn_sernum);
/* pairs with smp_wmb() in fib6_update_sernum_upto_root() */
smp_rmb();
status = true;
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -112,7 +112,7 @@ void fib6_update_sernum(struct net *net,
fn = rcu_dereference_protected(f6i->fib6_node,
lockdep_is_held(&f6i->fib6_table->tb6_lock));
if (fn)
- fn->fn_sernum = fib6_new_sernum(net);
+ WRITE_ONCE(fn->fn_sernum, fib6_new_sernum(net));
}

/*
@@ -544,12 +544,13 @@ static int fib6_dump_table(struct fib6_t
spin_unlock_bh(&table->tb6_lock);
if (res > 0) {
cb->args[4] = 1;
- cb->args[5] = w->root->fn_sernum;
+ cb->args[5] = READ_ONCE(w->root->fn_sernum);
}
} else {
- if (cb->args[5] != w->root->fn_sernum) {
+ int sernum = READ_ONCE(w->root->fn_sernum);
+ if (cb->args[5] != sernum) {
/* Begin at the root if the tree changed */
- cb->args[5] = w->root->fn_sernum;
+ cb->args[5] = sernum;
w->state = FWS_INIT;
w->node = w->root;
w->skip = w->count;
@@ -1203,7 +1204,7 @@ static void __fib6_update_sernum_upto_ro
/* paired with smp_rmb() in rt6_get_cookie_safe() */
smp_wmb();
while (fn) {
- fn->fn_sernum = sernum;
+ WRITE_ONCE(fn->fn_sernum, sernum);
fn = rcu_dereference_protected(fn->parent,
lockdep_is_held(&rt->fib6_table->tb6_lock));
}
@@ -1983,8 +1984,8 @@ static int fib6_clean_node(struct fib6_w
};

if (c->sernum != FIB6_NO_SERNUM_CHANGE &&
- w->node->fn_sernum != c->sernum)
- w->node->fn_sernum = c->sernum;
+ READ_ONCE(w->node->fn_sernum) != c->sernum)
+ WRITE_ONCE(w->node->fn_sernum, c->sernum);

if (!c->func) {
WARN_ON_ONCE(c->sernum == FIB6_NO_SERNUM_CHANGE);
@@ -2332,7 +2333,7 @@ static void ipv6_route_seq_setup_walk(st
iter->w.state = FWS_INIT;
iter->w.node = iter->w.root;
iter->w.args = iter;
- iter->sernum = iter->w.root->fn_sernum;
+ iter->sernum = READ_ONCE(iter->w.root->fn_sernum);
INIT_LIST_HEAD(&iter->w.lh);
fib6_walker_link(net, &iter->w);
}
@@ -2360,8 +2361,10 @@ static struct fib6_table *ipv6_route_seq

static void ipv6_route_check_sernum(struct ipv6_route_iter *iter)
{
- if (iter->sernum != iter->w.root->fn_sernum) {
- iter->sernum = iter->w.root->fn_sernum;
+ int sernum = READ_ONCE(iter->w.root->fn_sernum);
+
+ if (iter->sernum != sernum) {
+ iter->sernum = sernum;
iter->w.state = FWS_INIT;
iter->w.node = iter->w.root;
WARN_ON(iter->w.skip);
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2320,7 +2320,7 @@ static void ip6_link_failure(struct sk_b
if (from) {
fn = rcu_dereference(from->fib6_node);
if (fn && (rt->rt6i_flags & RTF_DEFAULT))
- fn->fn_sernum = -1;
+ WRITE_ONCE(fn->fn_sernum, -1);
}
}
rcu_read_unlock();