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Florian Westphal authored
syzbot reported yet another regression added with DOIT_UNLOCKED. When nexthop is marked as dead, fib_dump_info uses __in_dev_get_rtnl(): ./include/linux/inetdevice.h:230 suspicious rcu_dereference_protected() usage! rcu_scheduler_active = 2, debug_locks = 1 1 lock held by syz-executor2/23859: #0: (rcu_read_lock){....}, at: [<ffffffff840283f0>] inet_rtm_getroute+0xaa0/0x2d70 net/ipv4/route.c:2738 [..] lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4665 __in_dev_get_rtnl include/linux/inetdevice.h:230 [inline] fib_dump_info+0x1136/0x13d0 net/ipv4/fib_semantics.c:1377 inet_rtm_getroute+0xf97/0x2d70 net/ipv4/route.c:2785 .. This isn't safe anymore, callers either hold RTNL mutex or rcu read lock, so these spots must use rcu_dereference_rtnl() or plain rcu_derefence() (plus unconditional rcu read lock). This does the latter. Fixes: 394f51ab ("ipv4: route: set ipv4 RTM_GETROUTE to not use rtnl") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
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