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ipv6/addrconf: fix a null-ptr-deref bug for ip6_ptr 

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2164865
Upstream Status: net.git commit 85f0173df35e

commit 85f0173df35e5462d89947135a6a5599c6c3ef6f
Author: Ziyang Xuan <william.xuanziyang@huawei.com>
Date:   Thu Jul 28 09:33:07 2022 +0800

    ipv6/addrconf: fix a null-ptr-deref bug for ip6_ptr

    Change net device's MTU to smaller than IPV6_MIN_MTU or unregister
    device while matching route. That may trigger null-ptr-deref bug
    for ip6_ptr probability as following.

    =========================================================
    BUG: KASAN: null-ptr-deref in find_match.part.0+0x70/0x134
    Read of size 4 at addr 0000000000000308 by task ping6/263

    CPU: 2 PID: 263 Comm: ping6 Not tainted 5.19.0-rc7+ #14
    Call trace:
     dump_backtrace+0x1a8/0x230
     show_stack+0x20/0x70
     dump_stack_lvl+0x68/0x84
     print_report+0xc4/0x120
     kasan_report+0x84/0x120
     __asan_load4+0x94/0xd0
     find_match.part.0+0x70/0x134
     __find_rr_leaf+0x408/0x470
     fib6_table_lookup+0x264/0x540
     ip6_pol_route+0xf4/0x260
     ip6_pol_route_output+0x58/0x70
     fib6_rule_lookup+0x1a8/0x330
     ip6_route_output_flags_noref+0xd8/0x1a0
     ip6_route_output_flags+0x58/0x160
     ip6_dst_lookup_tail+0x5b4/0x85c
     ip6_dst_lookup_flow+0x98/0x120
     rawv6_sendmsg+0x49c/0xc70
     inet_sendmsg+0x68/0x94

    Reproducer as following:
    Firstly, prepare conditions:
    $ip netns add ns1
    $ip netns add ns2
    $ip link add veth1 type veth peer name veth2
    $ip link set veth1 netns ns1
    $ip link set veth2 netns ns2
    $ip netns exec ns1 ip -6 addr add 2001:0db8:0:f101::1/64 dev veth1
    $ip netns exec ns2 ip -6 addr add 2001:0db8:0:f101::2/64 dev veth2
    $ip netns exec ns1 ifconfig veth1 up
    $ip netns exec ns2 ifconfig veth2 up
    $ip netns exec ns1 ip -6 route add 2000::/64 dev veth1 metric 1
    $ip netns exec ns2 ip -6 route add 2001::/64 dev veth2 metric 1

    Secondly, execute the following two commands in two ssh windows
    respectively:
    $ip netns exec ns1 sh
    $while true; do ip -6 addr add 2001:0db8:0:f101::1/64 dev veth1; ip -6 route add 2000::/64 dev veth1 metric 1; ping6 2000::2; done

    $ip netns exec ns1 sh
    $while true; do ip link set veth1 mtu 1000; ip link set veth1 mtu 1500; sleep 5; done

    It is because ip6_ptr has been assigned to NULL in addrconf_ifdown() firstly,
    then ip6_ignore_linkdown() accesses ip6_ptr directly without NULL check.

            cpu0                    cpu1
    fib6_table_lookup
    __find_rr_leaf
                            addrconf_notify [ NETDEV_CHANGEMTU ]
                            addrconf_ifdown
                            RCU_INIT_POINTER(dev->ip6_ptr, NULL)
    find_match
    ip6_ignore_linkdown

    So we can add NULL check for ip6_ptr before using in ip6_ignore_linkdown() to
    fix the null-ptr-deref bug.

    Fixes: dcd1f57295 ("net/ipv6: Remove fib6_idev")
    Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
    Reviewed-by: David Ahern <dsahern@kernel.org>
    Link: https://lore.kernel.org/r/20220728013307.656257-1-william.xuanziyang@huawei.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
This commit is contained in:
Davide Caratti 2023-01-26 19:34:23 +01:00
parent cadc0a4901
commit 0a70e17477
1 changed files with 3 additions and 0 deletions
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3
include/net/addrconf.h
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@ -403,6 +403,9 @@ static inline bool ip6_ignore_linkdown(const struct net_device *dev)
{
const struct inet6_dev *idev = __in6_dev_get(dev);
if (unlikely(!idev))
return true;
return !!idev->cnf.ignore_routes_with_linkdown;
}