From: Eric Dumazet edumazet@google.com
commit 9fcf986cc4bc6a3a39f23fbcbbc3a9e52d3c24fd upstream.
fib_alias_hw_flags_set() can be used by concurrent threads, and is only RCU protected.
We need to annotate accesses to following fields of struct fib_alias:
offload, trap, offload_failed
Because of READ_ONCE()WRITE_ONCE() limitations, make these field u8.
BUG: KCSAN: data-race in fib_alias_hw_flags_set / fib_alias_hw_flags_set
read to 0xffff888134224a6a of 1 bytes by task 2013 on cpu 1: fib_alias_hw_flags_set+0x28a/0x470 net/ipv4/fib_trie.c:1050 nsim_fib4_rt_hw_flags_set drivers/net/netdevsim/fib.c:350 [inline] nsim_fib4_rt_add drivers/net/netdevsim/fib.c:367 [inline] nsim_fib4_rt_insert drivers/net/netdevsim/fib.c:429 [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+0x1852/0x2cf0 drivers/net/netdevsim/fib.c:1477 process_one_work+0x3f6/0x960 kernel/workqueue.c:2307 process_scheduled_works kernel/workqueue.c:2370 [inline] worker_thread+0x7df/0xa70 kernel/workqueue.c:2456 kthread+0x1bf/0x1e0 kernel/kthread.c:377 ret_from_fork+0x1f/0x30
write to 0xffff888134224a6a of 1 bytes by task 4872 on cpu 0: fib_alias_hw_flags_set+0x2d5/0x470 net/ipv4/fib_trie.c:1054 nsim_fib4_rt_hw_flags_set drivers/net/netdevsim/fib.c:350 [inline] nsim_fib4_rt_add drivers/net/netdevsim/fib.c:367 [inline] nsim_fib4_rt_insert drivers/net/netdevsim/fib.c:429 [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+0x1852/0x2cf0 drivers/net/netdevsim/fib.c:1477 process_one_work+0x3f6/0x960 kernel/workqueue.c:2307 process_scheduled_works kernel/workqueue.c:2370 [inline] worker_thread+0x7df/0xa70 kernel/workqueue.c:2456 kthread+0x1bf/0x1e0 kernel/kthread.c:377 ret_from_fork+0x1f/0x30
value changed: 0x00 -> 0x02
Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 4872 Comm: kworker/0:0 Not tainted 5.17.0-rc3-syzkaller-00188-g1d41d2e82623-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events nsim_fib_event_work
Fixes: 90b93f1b31f8 ("ipv4: Add "offload" and "trap" indications to routes") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Reviewed-by: Ido Schimmel idosch@nvidia.com Link: https://lore.kernel.org/r/20220216173217.3792411-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/fib_lookup.h | 7 +++---- net/ipv4/fib_semantics.c | 6 +++--- net/ipv4/fib_trie.c | 22 +++++++++++++--------- net/ipv4/route.c | 4 ++-- 4 files changed, 21 insertions(+), 18 deletions(-)
--- a/net/ipv4/fib_lookup.h +++ b/net/ipv4/fib_lookup.h @@ -16,10 +16,9 @@ struct fib_alias { u8 fa_slen; u32 tb_id; s16 fa_default; - u8 offload:1, - trap:1, - offload_failed:1, - unused:5; + u8 offload; + u8 trap; + u8 offload_failed; struct rcu_head rcu; };
--- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -524,9 +524,9 @@ void rtmsg_fib(int event, __be32 key, st fri.dst_len = dst_len; fri.tos = fa->fa_tos; fri.type = fa->fa_type; - fri.offload = fa->offload; - fri.trap = fa->trap; - fri.offload_failed = fa->offload_failed; + fri.offload = READ_ONCE(fa->offload); + fri.trap = READ_ONCE(fa->trap); + fri.offload_failed = READ_ONCE(fa->offload_failed); err = fib_dump_info(skb, info->portid, seq, event, &fri, nlm_flags); if (err < 0) { /* -EMSGSIZE implies BUG in fib_nlmsg_size() */ --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -1047,19 +1047,23 @@ void fib_alias_hw_flags_set(struct net * if (!fa_match) goto out;
- if (fa_match->offload == fri->offload && fa_match->trap == fri->trap && - fa_match->offload_failed == fri->offload_failed) + /* These are paired with the WRITE_ONCE() happening in this function. + * The reason is that we are only protected by RCU at this point. + */ + if (READ_ONCE(fa_match->offload) == fri->offload && + READ_ONCE(fa_match->trap) == fri->trap && + READ_ONCE(fa_match->offload_failed) == fri->offload_failed) goto out;
- fa_match->offload = fri->offload; - fa_match->trap = fri->trap; + WRITE_ONCE(fa_match->offload, fri->offload); + WRITE_ONCE(fa_match->trap, fri->trap);
/* 2 means send notifications only if offload_failed was changed. */ if (net->ipv4.sysctl_fib_notify_on_flag_change == 2 && - fa_match->offload_failed == fri->offload_failed) + READ_ONCE(fa_match->offload_failed) == fri->offload_failed) goto out;
- fa_match->offload_failed = fri->offload_failed; + WRITE_ONCE(fa_match->offload_failed, fri->offload_failed);
if (!net->ipv4.sysctl_fib_notify_on_flag_change) goto out; @@ -2297,9 +2301,9 @@ static int fn_trie_dump_leaf(struct key_ fri.dst_len = KEYLENGTH - fa->fa_slen; fri.tos = fa->fa_tos; fri.type = fa->fa_type; - fri.offload = fa->offload; - fri.trap = fa->trap; - fri.offload_failed = fa->offload_failed; + fri.offload = READ_ONCE(fa->offload); + fri.trap = READ_ONCE(fa->trap); + fri.offload_failed = READ_ONCE(fa->offload_failed); err = fib_dump_info(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq, --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -3393,8 +3393,8 @@ static int inet_rtm_getroute(struct sk_b fa->fa_tos == fri.tos && fa->fa_info == res.fi && fa->fa_type == fri.type) { - fri.offload = fa->offload; - fri.trap = fa->trap; + fri.offload = READ_ONCE(fa->offload); + fri.trap = READ_ONCE(fa->trap); break; } }