5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
commit 195374d893681da43a39796e53b30ac4f20400c4 upstream.
syzbot reported a data-race while accessing nh->nh_saddr_genid [1]
Add annotations, but leave the code lazy as intended.
[1] BUG: KCSAN: data-race in fib_select_path / fib_select_path
write to 0xffff8881387166f0 of 4 bytes by task 6778 on cpu 1: fib_info_update_nhc_saddr net/ipv4/fib_semantics.c:1334 [inline] fib_result_prefsrc net/ipv4/fib_semantics.c:1354 [inline] fib_select_path+0x292/0x330 net/ipv4/fib_semantics.c:2269 ip_route_output_key_hash_rcu+0x659/0x12c0 net/ipv4/route.c:2810 ip_route_output_key_hash net/ipv4/route.c:2644 [inline] __ip_route_output_key include/net/route.h:134 [inline] ip_route_output_flow+0xa6/0x150 net/ipv4/route.c:2872 send4+0x1f5/0x520 drivers/net/wireguard/socket.c:61 wg_socket_send_skb_to_peer+0x94/0x130 drivers/net/wireguard/socket.c:175 wg_socket_send_buffer_to_peer+0xd6/0x100 drivers/net/wireguard/socket.c:200 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline] wg_packet_handshake_send_worker+0x10c/0x150 drivers/net/wireguard/send.c:51 process_one_work kernel/workqueue.c:2630 [inline] process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703 worker_thread+0x525/0x730 kernel/workqueue.c:2784 kthread+0x1d7/0x210 kernel/kthread.c:388 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
read to 0xffff8881387166f0 of 4 bytes by task 6759 on cpu 0: fib_result_prefsrc net/ipv4/fib_semantics.c:1350 [inline] fib_select_path+0x1cb/0x330 net/ipv4/fib_semantics.c:2269 ip_route_output_key_hash_rcu+0x659/0x12c0 net/ipv4/route.c:2810 ip_route_output_key_hash net/ipv4/route.c:2644 [inline] __ip_route_output_key include/net/route.h:134 [inline] ip_route_output_flow+0xa6/0x150 net/ipv4/route.c:2872 send4+0x1f5/0x520 drivers/net/wireguard/socket.c:61 wg_socket_send_skb_to_peer+0x94/0x130 drivers/net/wireguard/socket.c:175 wg_socket_send_buffer_to_peer+0xd6/0x100 drivers/net/wireguard/socket.c:200 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline] wg_packet_handshake_send_worker+0x10c/0x150 drivers/net/wireguard/send.c:51 process_one_work kernel/workqueue.c:2630 [inline] process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703 worker_thread+0x525/0x730 kernel/workqueue.c:2784 kthread+0x1d7/0x210 kernel/kthread.c:388 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
value changed: 0x959d3217 -> 0x959d3218
Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 6759 Comm: kworker/u4:15 Not tainted 6.6.0-rc4-syzkaller-00029-gcbf3a2cb156a #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023 Workqueue: wg-kex-wg1 wg_packet_handshake_send_worker
Fixes: 436c3b66ec98 ("ipv4: Invalidate nexthop cache nh_saddr more correctly.") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Eric Dumazet edumazet@google.com Reviewed-by: Simon Horman horms@kernel.org Reviewed-by: David Ahern dsahern@kernel.org Link: https://lore.kernel.org/r/20231017192304.82626-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/fib_semantics.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
--- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -1333,15 +1333,18 @@ __be32 fib_info_update_nhc_saddr(struct unsigned char scope) { struct fib_nh *nh; + __be32 saddr;
if (nhc->nhc_family != AF_INET) return inet_select_addr(nhc->nhc_dev, 0, scope);
nh = container_of(nhc, struct fib_nh, nh_common); - nh->nh_saddr = inet_select_addr(nh->fib_nh_dev, nh->fib_nh_gw4, scope); - nh->nh_saddr_genid = atomic_read(&net->ipv4.dev_addr_genid); + saddr = inet_select_addr(nh->fib_nh_dev, nh->fib_nh_gw4, scope);
- return nh->nh_saddr; + WRITE_ONCE(nh->nh_saddr, saddr); + WRITE_ONCE(nh->nh_saddr_genid, atomic_read(&net->ipv4.dev_addr_genid)); + + return saddr; }
__be32 fib_result_prefsrc(struct net *net, struct fib_result *res) @@ -1355,8 +1358,9 @@ __be32 fib_result_prefsrc(struct net *ne struct fib_nh *nh;
nh = container_of(nhc, struct fib_nh, nh_common); - if (nh->nh_saddr_genid == atomic_read(&net->ipv4.dev_addr_genid)) - return nh->nh_saddr; + if (READ_ONCE(nh->nh_saddr_genid) == + atomic_read(&net->ipv4.dev_addr_genid)) + return READ_ONCE(nh->nh_saddr); }
return fib_info_update_nhc_saddr(net, nhc, res->fi->fib_scope);