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From: syzbot ci To: davem@davemloft.net, dsahern@kernel.org, edumazet@kernel.org, horms@kernel.org, idosch@nvidia.com, kuba@kernel.org, kuni1840@gmail.com, kuniyu@google.com, netdev@vger.kernel.org, pabeni@redhat.com, syzbot@syzkaller.appspotmail.com Cc: syzbot@lists.linux.dev, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot ci has tested the following series [v1] ipv6: Protect multiple routes insertion by table lock. https://lore.kernel.org/all/20261023191517.607834-1-kuniyu@google.com * [PATCH v1 net] ipv6: Protect multiple routes insertion by table lock. and found the following issue: WARNING: suspicious RCU usage in rt6_multipath_rebalance Full report is available here: https://ci.syzbot.org/series/7d878fa2-f84a-4468-85e2-c2a5e263aeff *** WARNING: suspicious RCU usage in rt6_multipath_rebalance tree: net URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git base: 7076f684d5132e6a6145e1da2fa74771ecd052e5 arch: amd64 compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 config: https://ci.syzbot.org/builds/bbb3053f-f23f-4fe3-a9e9-85396428119d/config IPv6: RTM_NEWROUTE with no NLM_F_CREATE or NLM_F_REPLACE IPv6: NLM_F_CREATE should be set when creating new route ============================= WARNING: suspicious RCU usage syzkaller #0 Not tainted ----------------------------- ./include/net/addrconf.h:351 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 locks held by syz.2.3386/18922: 1, last CPU#0: #0: ffff888177df3430 (&tb->tb6_lock){+...}-{3:3}, at: inet6_rtm_newroute+0x3dc/0x1ab0 stack backtrace: CPU: 0 UID: 0 PID: 18922 Comm: syz.2.3386 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Call Trace: dump_stack_lvl+0xe8/0x150 lockdep_rcu_suspicious+0x140/0x1d0 rt6_multipath_rebalance+0xf11/0x1080 fib6_del+0xada/0x15a0 inet6_rtm_newroute+0x15b5/0x1ab0 rtnetlink_rcv_msg+0x802/0xc00 netlink_rcv_skb+0x226/0x4a0 netlink_unicast+0x8ef/0xa80 netlink_sendmsg+0x7f0/0xb20 sock_sendmsg_nosec+0x14e/0x190 ____sys_sendmsg+0x54e/0x850 ___sys_sendmsg+0x2a5/0x360 __sys_sendmmsg+0x273/0x4e0 __x64_sys_sendmmsg+0xa0/0xc0 do_syscall_64+0x166/0x520 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa77459f559 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fa775488028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007fa774826090 RCX: 00007fa77459f559 RDX: 040000000000009f RSI: 00002000000002c0 RDI: 000000000000000b RBP: 00007fa774636b20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa774826128 R14: 00007fa774826090 R15: 00007fffd26b46d8 *** If these findings have caused you to resend the series or submit a separate fix, please add the following tag to your commit message: Tested-by: syzbot@syzkaller.appspotmail.com --- This report is generated by a bot. It may contain errors. syzbot ci engineers can be reached at syzkaller@googlegroups.com. To test a fix for this bug, please reply with `#syz test` (on a separate line) and attach the patch to the email. Notes: - The patch will be applied on top of the tested series (as an incremental fix). - To test a new version of the whole series, please send it directly to syzbot@lists.linux.dev. - Arguments like custom git repos and branches are not supported.