| Message ID | 20210310022035.2908294-1-weiwan@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 28259bac7f1dde06d8ba324e222bbec9d4e92f2b |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v2] ipv6: fix suspecious RCU usage warning | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 1 maintainers not CCed: yoshfuji@linux-ipv6.org |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 636 this patch: 636 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 44 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 661 this patch: 661 |
| netdev/header_inline | success | Link |
On Tue, Mar 09, 2021 at 06:20:35PM -0800, Wei Wang wrote: > 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 [...] > > 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>
On 3/9/21 7:20 PM, Wei Wang wrote: > 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(). > ... > > 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> > --- > include/net/nexthop.h | 24 ++++++++++++++++++++++++ > net/ipv6/ip6_fib.c | 2 +- > 2 files changed, 25 insertions(+), 1 deletion(-) > Reviewed-by: David Ahern <dsahern@kernel.org> Thanks, Wei.
Hello: This patch was applied to netdev/net.git (refs/heads/master): On Tue, 9 Mar 2021 18:20:35 -0800 you wrote: > 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(). > > [...] Here is the summary with links: - [net,v2] ipv6: fix suspecious RCU usage warning https://git.kernel.org/netdev/net/c/28259bac7f1d You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
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; diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index ef9d022e693f..679699e953f1 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -2486,7 +2486,7 @@ static int ipv6_route_native_seq_show(struct seq_file *seq, void *v) const struct net_device *dev; if (rt->nh) - fib6_nh = nexthop_fib6_nh(rt->nh); + fib6_nh = nexthop_fib6_nh_bh(rt->nh); seq_printf(seq, "%pi6 %02x ", &rt->fib6_dst.addr, rt->fib6_dst.plen);
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> --- include/net/nexthop.h | 24 ++++++++++++++++++++++++ net/ipv6/ip6_fib.c | 2 +- 2 files changed, 25 insertions(+), 1 deletion(-)