diff options
author | Wei Wang <weiwan@google.com> | 2021-03-09 18:20:35 -0800 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2021-03-10 12:35:23 -0800 |
commit | 28259bac7f1dde06d8ba324e222bbec9d4e92f2b (patch) | |
tree | e86e9f21b956aa83998e9a90339977de52b459fd /include/net | |
parent | c89489b47289e222c4363c20515e0ac321acbae4 (diff) | |
download | linux-28259bac7f1dde06d8ba324e222bbec9d4e92f2b.tar.bz2 |
ipv6: fix suspecious RCU usage warning
Syzbot reported the suspecious RCU usage in nexthop_fib6_nh() when
called from ipv6_route_seq_show(). The reason is ipv6_route_seq_start()
calls rcu_read_lock_bh(), while nexthop_fib6_nh() calls
rcu_dereference_rtnl().
The fix proposed is to add a variant of nexthop_fib6_nh() to use
rcu_dereference_bh_rtnl() for ipv6_route_seq_show().
The reported trace is as follows:
./include/net/nexthop.h:416 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
2 locks held by syz-executor.0/17895:
at: seq_read+0x71/0x12a0 fs/seq_file.c:169
at: seq_file_net include/linux/seq_file_net.h:19 [inline]
at: ipv6_route_seq_start+0xaf/0x300 net/ipv6/ip6_fib.c:2616
stack backtrace:
CPU: 1 PID: 17895 Comm: syz-executor.0 Not tainted 4.15.0-syzkaller #0
Call Trace:
[<ffffffff849edf9e>] __dump_stack lib/dump_stack.c:17 [inline]
[<ffffffff849edf9e>] dump_stack+0xd8/0x147 lib/dump_stack.c:53
[<ffffffff8480b7fa>] lockdep_rcu_suspicious+0x153/0x15d kernel/locking/lockdep.c:5745
[<ffffffff8459ada6>] nexthop_fib6_nh include/net/nexthop.h:416 [inline]
[<ffffffff8459ada6>] ipv6_route_native_seq_show net/ipv6/ip6_fib.c:2488 [inline]
[<ffffffff8459ada6>] ipv6_route_seq_show+0x436/0x7a0 net/ipv6/ip6_fib.c:2673
[<ffffffff81c556df>] seq_read+0xccf/0x12a0 fs/seq_file.c:276
[<ffffffff81dbc62c>] proc_reg_read+0x10c/0x1d0 fs/proc/inode.c:231
[<ffffffff81bc28ae>] do_loop_readv_writev fs/read_write.c:714 [inline]
[<ffffffff81bc28ae>] do_loop_readv_writev fs/read_write.c:701 [inline]
[<ffffffff81bc28ae>] do_iter_read+0x49e/0x660 fs/read_write.c:935
[<ffffffff81bc81ab>] vfs_readv+0xfb/0x170 fs/read_write.c:997
[<ffffffff81c88847>] kernel_readv fs/splice.c:361 [inline]
[<ffffffff81c88847>] default_file_splice_read+0x487/0x9c0 fs/splice.c:416
[<ffffffff81c86189>] do_splice_to+0x129/0x190 fs/splice.c:879
[<ffffffff81c86f66>] splice_direct_to_actor+0x256/0x890 fs/splice.c:951
[<ffffffff81c8777d>] do_splice_direct+0x1dd/0x2b0 fs/splice.c:1060
[<ffffffff81bc4747>] do_sendfile+0x597/0xce0 fs/read_write.c:1459
[<ffffffff81bca205>] SYSC_sendfile64 fs/read_write.c:1520 [inline]
[<ffffffff81bca205>] SyS_sendfile64+0x155/0x170 fs/read_write.c:1506
[<ffffffff81015fcf>] do_syscall_64+0x1ff/0x310 arch/x86/entry/common.c:305
[<ffffffff84a00076>] entry_SYSCALL_64_after_hwframe+0x42/0xb7
Fixes: f88d8ea67fbdb ("ipv6: Plumb support for nexthop object in a fib6_info")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Wei Wang <weiwan@google.com>
Cc: David Ahern <dsahern@kernel.org>
Cc: Ido Schimmel <idosch@idosch.org>
Cc: Petr Machata <petrm@nvidia.com>
Cc: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net')
-rw-r--r-- | include/net/nexthop.h | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/include/net/nexthop.h b/include/net/nexthop.h index 7bc057aee40b..a10a319d7eb2 100644 --- a/include/net/nexthop.h +++ b/include/net/nexthop.h @@ -410,6 +410,7 @@ static inline struct fib_nh *fib_info_nh(struct fib_info *fi, int nhsel) int fib6_check_nexthop(struct nexthop *nh, struct fib6_config *cfg, struct netlink_ext_ack *extack); +/* Caller should either hold rcu_read_lock(), or RTNL. */ static inline struct fib6_nh *nexthop_fib6_nh(struct nexthop *nh) { struct nh_info *nhi; @@ -430,6 +431,29 @@ static inline struct fib6_nh *nexthop_fib6_nh(struct nexthop *nh) return NULL; } +/* Variant of nexthop_fib6_nh(). + * Caller should either hold rcu_read_lock_bh(), or RTNL. + */ +static inline struct fib6_nh *nexthop_fib6_nh_bh(struct nexthop *nh) +{ + struct nh_info *nhi; + + if (nh->is_group) { + struct nh_group *nh_grp; + + nh_grp = rcu_dereference_bh_rtnl(nh->nh_grp); + nh = nexthop_mpath_select(nh_grp, 0); + if (!nh) + return NULL; + } + + nhi = rcu_dereference_bh_rtnl(nh->nh_info); + if (nhi->family == AF_INET6) + return &nhi->fib6_nh; + + return NULL; +} + static inline struct net_device *fib6_info_nh_dev(struct fib6_info *f6i) { struct fib6_nh *fib6_nh; |