5.4-stable review patch. If anyone has any objections, please let me know.
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From: Stefan Wiehler stefan.wiehler@nokia.com
[ Upstream commit 38f50242bf0f237cdc262308d624d333286ec3c5 ]
With CONFIG_PROVE_RCU_LIST=y and by executing
$ netcat -l --sctp & $ netcat --sctp localhost & $ ss --sctp
one can trigger the following Lockdep-RCU splat(s):
WARNING: suspicious RCU usage 6.18.0-rc1-00093-g7f864458e9a6 #5 Not tainted ----------------------------- net/sctp/diag.c:76 RCU-list traversed in non-reader section!!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1 2 locks held by ss/215: #0: ffff9c740828bec0 (nlk_cb_mutex-SOCK_DIAG){+.+.}-{4:4}, at: __netlink_dump_start+0x84/0x2b0 #1: ffff9c7401d72cd0 (sk_lock-AF_INET6){+.+.}-{0:0}, at: sctp_sock_dump+0x38/0x200
stack backtrace: CPU: 0 UID: 0 PID: 215 Comm: ss Not tainted 6.18.0-rc1-00093-g7f864458e9a6 #5 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x5d/0x90 lockdep_rcu_suspicious.cold+0x4e/0xa3 inet_sctp_diag_fill.isra.0+0x4b1/0x5d0 sctp_sock_dump+0x131/0x200 sctp_transport_traverse_process+0x170/0x1b0 ? __pfx_sctp_sock_filter+0x10/0x10 ? __pfx_sctp_sock_dump+0x10/0x10 sctp_diag_dump+0x103/0x140 __inet_diag_dump+0x70/0xb0 netlink_dump+0x148/0x490 __netlink_dump_start+0x1f3/0x2b0 inet_diag_handler_cmd+0xcd/0x100 ? __pfx_inet_diag_dump_start+0x10/0x10 ? __pfx_inet_diag_dump+0x10/0x10 ? __pfx_inet_diag_dump_done+0x10/0x10 sock_diag_rcv_msg+0x18e/0x320 ? __pfx_sock_diag_rcv_msg+0x10/0x10 netlink_rcv_skb+0x4d/0x100 netlink_unicast+0x1d7/0x2b0 netlink_sendmsg+0x203/0x450 ____sys_sendmsg+0x30c/0x340 ___sys_sendmsg+0x94/0xf0 __sys_sendmsg+0x83/0xf0 do_syscall_64+0xbb/0x390 entry_SYSCALL_64_after_hwframe+0x77/0x7f ... </TASK>
Fixes: 8f840e47f190 ("sctp: add the sctp_diag.c file") Signed-off-by: Stefan Wiehler stefan.wiehler@nokia.com Reviewed-by: Kuniyuki Iwashima kuniyu@google.com Acked-by: Xin Long lucien.xin@gmail.com Link: https://patch.msgid.link/20251028161506.3294376-2-stefan.wiehler@nokia.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/sctp/diag.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/net/sctp/diag.c b/net/sctp/diag.c index 2fcfb8cc8bd12..fd7a55b3049db 100644 --- a/net/sctp/diag.c +++ b/net/sctp/diag.c @@ -73,19 +73,23 @@ static int inet_diag_msg_sctpladdrs_fill(struct sk_buff *skb, struct nlattr *attr; void *info = NULL;
+ rcu_read_lock(); list_for_each_entry_rcu(laddr, address_list, list) addrcnt++; + rcu_read_unlock();
attr = nla_reserve(skb, INET_DIAG_LOCALS, addrlen * addrcnt); if (!attr) return -EMSGSIZE;
info = nla_data(attr); + rcu_read_lock(); list_for_each_entry_rcu(laddr, address_list, list) { memcpy(info, &laddr->a, sizeof(laddr->a)); memset(info + sizeof(laddr->a), 0, addrlen - sizeof(laddr->a)); info += addrlen; } + rcu_read_unlock();
return 0; }