The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.14.y git checkout FETCH_HEAD git cherry-pick -x 195374d893681da43a39796e53b30ac4f20400c4 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023102032-fang-urban-2541@gregkh' --subject-prefix 'PATCH 4.14.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 195374d893681da43a39796e53b30ac4f20400c4 Mon Sep 17 00:00:00 2001 From: Eric Dumazet <edumazet@xxxxxxxxxx> Date: Tue, 17 Oct 2023 19:23:04 +0000 Subject: [PATCH] ipv4: fib: annotate races around nh->nh_saddr_genid and nh->nh_saddr 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@xxxxxxxxxxxxxxxx> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx> Reviewed-by: Simon Horman <horms@xxxxxxxxxx> Reviewed-by: David Ahern <dsahern@xxxxxxxxxx> Link: https://lore.kernel.org/r/20231017192304.82626-1-edumazet@xxxxxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index 1ea82bc33ef1..5eb1b8d302bb 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -1325,15 +1325,18 @@ __be32 fib_info_update_nhc_saddr(struct net *net, struct fib_nh_common *nhc, 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) @@ -1347,8 +1350,9 @@ __be32 fib_result_prefsrc(struct net *net, struct fib_result *res) 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);
