67ea41d19d
I missed that inet6_dump_addr() is calling in6_dump_addrs() from two points. First one under RTNL protection, and second one under rcu_read_lock(). Since we want to remove RTNL use from inet6_dump_addr() very soon, no longer assume in6_dump_addrs() is protected by RTNL (even if this is still the case). Use rcu_read_lock() earlier to fix this lockdep splat: WARNING: suspicious RCU usage 6.8.0-rc5-syzkaller-01618-gf8cbf6bde4c8 #0 Not tainted net/ipv6/addrconf.c:5317 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by syz-executor.2/8834: #0: ffff88802f554678 (nlk_cb_mutex-ROUTE){+.+.}-{3:3}, at: __netlink_dump_start+0x119/0x780 net/netlink/af_netlink.c:2338 #1: ffffffff8f377a88 (rtnl_mutex){+.+.}-{3:3}, at: netlink_dump+0x676/0xda0 net/netlink/af_netlink.c:2265 #2: ffff88807e5f0580 (&ndev->lock){++--}-{2:2}, at: in6_dump_addrs+0xb8/0x1de0 net/ipv6/addrconf.c:5279 stack backtrace: CPU: 1 PID: 8834 Comm: syz-executor.2 Not tainted 6.8.0-rc5-syzkaller-01618-gf8cbf6bde4c8 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106 lockdep_rcu_suspicious+0x220/0x340 kernel/locking/lockdep.c:6712 in6_dump_addrs+0x1b47/0x1de0 net/ipv6/addrconf.c:5317 inet6_dump_addr+0x1597/0x1690 net/ipv6/addrconf.c:5428 netlink_dump+0x6a6/0xda0 net/netlink/af_netlink.c:2266 __netlink_dump_start+0x59d/0x780 net/netlink/af_netlink.c:2374 netlink_dump_start include/linux/netlink.h:340 [inline] rtnetlink_rcv_msg+0xcf7/0x10d0 net/core/rtnetlink.c:6555 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2547 netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline] netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1361 netlink_sendmsg+0x8e0/0xcb0 net/netlink/af_netlink.c:1902 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:745 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2584 ___sys_sendmsg net/socket.c:2638 [inline] __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2667 Fixes: c3718936ec47 ("ipv6: anycast: complete RCU handling of struct ifacaddr6") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Jiri Pirko <jiri@nvidia.com> Link: https://lore.kernel.org/r/20240227222259.4081489-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.