• Patrick McHardy's avatar
    ipv6: fib: fix crash when changing large fib while dumping it · 2bec5a36
    Patrick McHardy authored
    
    
    When the fib size exceeds what can be dumped in a single skb, the
    dump is suspended and resumed once the last skb has been received
    by userspace. When the fib is changed while the dump is suspended,
    the walker might contain stale pointers, causing a crash when the
    dump is resumed.
    
    BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
    IP: [<ffffffffa01bce04>] fib6_walk_continue+0xbb/0x124 [ipv6]
    PGD 5347a067 PUD 65c7067 PMD 0
    Oops: 0000 [#1] PREEMPT SMP
    ...
    RIP: 0010:[<ffffffffa01bce04>]
    [<ffffffffa01bce04>] fib6_walk_continue+0xbb/0x124 [ipv6]
    ...
    Call Trace:
     [<ffffffff8104aca3>] ? mutex_spin_on_owner+0x59/0x71
     [<ffffffffa01bd105>] inet6_dump_fib+0x11b/0x1b9 [ipv6]
     [<ffffffff81371af4>] netlink_dump+0x5b/0x19e
     [<ffffffff8134f288>] ? consume_skb+0x28/0x2a
     [<ffffffff81373b69>] netlink_recvmsg+0x1ab/0x2c6
     [<ffffffff81372781>] ? netlink_unicast+0xfa/0x151
     [<ffffffff813483e0>] __sock_recvmsg+0x6d/0x79
     [<ffffffff81348a53>] sock_recvmsg+0xca/0xe3
     [<ffffffff81066d4b>] ? autoremove_wake_function+0x0/0x38
     [<ffffffff811ed1f8>] ? radix_tree_lookup_slot+0xe/0x10
     [<ffffffff810b3ed7>] ? find_get_page+0x90/0xa5
     [<ffffffff810b5dc5>] ? filemap_fault+0x201/0x34f
     [<ffffffff810ef152>] ? fget_light+0x2f/0xac
     [<ffffffff813519e7>] ? verify_iovec+0x4f/0x94
     [<ffffffff81349a65>] sys_recvmsg+0x14d/0x223
    
    Store the serial number when beginning to walk the fib and reload
    pointers when continuing to walk after a change occured. Similar
    to other dumping functions, this might cause unrelated entries to
    be missed when entries are deleted.
    Tested-by: default avatarBen Greear <greearb@candelatech.com>
    Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    2bec5a36
ip6_fib.c 32.6 KB