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 @@ -280,7 +280,7 @@ 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 @@ -110,7 +110,7 @@ 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)); }
/* @@ -587,12 +587,13 @@ 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; @@ -1342,7 +1343,7 @@ 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)); } @@ -2171,8 +2172,8 @@ 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); @@ -2536,7 +2537,7 @@ 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); } @@ -2564,8 +2565,10 @@ 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 @@ -2674,7 +2674,7 @@ 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();