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Date: Fri, 14 Jan 2022 07:39:02 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org> Cc: netdev <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Eric Dumazet <eric.dumazet@...il.com>, syzbot <syzkaller@...glegroups.com>, Ido Schimmel <idosch@...lanox.com>, Jiri Pirko <jiri@...lanox.com> Subject: [PATCH net] ipv4: make fib_info_cnt atomic From: Eric Dumazet <edumazet@...gle.com> Instead of making sure all free_fib_info() callers hold rtnl, it seems better to convert fib_info_cnt to an atomic_t. BUG: KCSAN: data-race in fib_create_info / free_fib_info write to 0xffffffff86e243a0 of 4 bytes by task 26429 on cpu 0: fib_create_info+0xe78/0x3440 net/ipv4/fib_semantics.c:1428 fib_table_insert+0x148/0x10c0 net/ipv4/fib_trie.c:1224 fib_magic+0x195/0x1e0 net/ipv4/fib_frontend.c:1087 fib_add_ifaddr+0xd0/0x2e0 net/ipv4/fib_frontend.c:1109 fib_netdev_event+0x178/0x510 net/ipv4/fib_frontend.c:1466 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0x53/0xb0 kernel/notifier.c:391 __dev_notify_flags+0x1d3/0x3b0 dev_change_flags+0xa2/0xc0 net/core/dev.c:8872 do_setlink+0x810/0x2410 net/core/rtnetlink.c:2719 rtnl_group_changelink net/core/rtnetlink.c:3242 [inline] __rtnl_newlink net/core/rtnetlink.c:3396 [inline] rtnl_newlink+0xb10/0x13b0 net/core/rtnetlink.c:3506 rtnetlink_rcv_msg+0x745/0x7e0 net/core/rtnetlink.c:5571 netlink_rcv_skb+0x14e/0x250 net/netlink/af_netlink.c:2496 rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5589 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x5fc/0x6c0 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x726/0x840 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:704 [inline] sock_sendmsg net/socket.c:724 [inline] ____sys_sendmsg+0x39a/0x510 net/socket.c:2409 ___sys_sendmsg net/socket.c:2463 [inline] __sys_sendmsg+0x195/0x230 net/socket.c:2492 __do_sys_sendmsg net/socket.c:2501 [inline] __se_sys_sendmsg net/socket.c:2499 [inline] __x64_sys_sendmsg+0x42/0x50 net/socket.c:2499 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 read to 0xffffffff86e243a0 of 4 bytes by task 31505 on cpu 1: free_fib_info+0x35/0x80 net/ipv4/fib_semantics.c:252 fib_info_put include/net/ip_fib.h:575 [inline] nsim_fib4_rt_destroy drivers/net/netdevsim/fib.c:294 [inline] nsim_fib4_rt_replace drivers/net/netdevsim/fib.c:403 [inline] nsim_fib4_rt_insert drivers/net/netdevsim/fib.c:431 [inline] nsim_fib4_event drivers/net/netdevsim/fib.c:461 [inline] nsim_fib_event drivers/net/netdevsim/fib.c:881 [inline] nsim_fib_event_work+0x15ca/0x2cf0 drivers/net/netdevsim/fib.c:1477 process_one_work+0x3fc/0x980 kernel/workqueue.c:2298 process_scheduled_works kernel/workqueue.c:2361 [inline] worker_thread+0x7df/0xa70 kernel/workqueue.c:2447 kthread+0x2c7/0x2e0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 value changed: 0x00000d2d -> 0x00000d2e Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 31505 Comm: kworker/1:21 Not tainted 5.16.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events nsim_fib_event_work Fixes: 48bb9eb47b27 ("netdevsim: fib: Add dummy implementation for FIB offload") Signed-off-by: Eric Dumazet <edumazet@...gle.com> Reported-by: syzbot <syzkaller@...glegroups.com> Cc: Ido Schimmel <idosch@...lanox.com> Cc: Jiri Pirko <jiri@...lanox.com> --- net/ipv4/fib_semantics.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index 828de171708f599b56f63715514c0259c7cb08a2..302373acf232205c812d10a041a87f22a64b1017 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -51,7 +51,7 @@ static DEFINE_SPINLOCK(fib_info_lock); static struct hlist_head *fib_info_hash; static struct hlist_head *fib_info_laddrhash; static unsigned int fib_info_hash_size; -static unsigned int fib_info_cnt; +static atomic_t fib_info_cnt; #define DEVINDEX_HASHBITS 8 #define DEVINDEX_HASHSIZE (1U << DEVINDEX_HASHBITS) @@ -249,7 +249,7 @@ void free_fib_info(struct fib_info *fi) pr_warn("Freeing alive fib_info %p\n", fi); return; } - fib_info_cnt--; + atomic_dec(&fib_info_cnt); call_rcu(&fi->rcu, free_fib_info_rcu); } @@ -1430,7 +1430,7 @@ struct fib_info *fib_create_info(struct fib_config *cfg, #endif err = -ENOBUFS; - if (fib_info_cnt >= fib_info_hash_size) { + if (atomic_read(&fib_info_cnt) >= fib_info_hash_size) { unsigned int new_size = fib_info_hash_size << 1; struct hlist_head *new_info_hash; struct hlist_head *new_laddrhash; @@ -1462,7 +1462,7 @@ struct fib_info *fib_create_info(struct fib_config *cfg, return ERR_PTR(err); } - fib_info_cnt++; + atomic_inc(&fib_info_cnt); fi->fib_net = net; fi->fib_protocol = cfg->fc_protocol; fi->fib_scope = cfg->fc_scope; -- 2.34.1.703.g22d0c6ccf7-goog
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