TLDRVuln - Cybersecurity Vulnerabilities Made Simple

In the Linux kernel, the following vulnerability has been resolved:

ipv6: Fix a potential NPD in cleanup_prefix_route()

addrconf_get_prefix_route() can return the fib6_null_entry sentinel

entry which has a NULL fib6_table pointer. Therefore, before setting the

route's expiration time, check that we are not working with this entry,

as otherwise a NPD will be triggered [1].

Note that the other callers of addrconf_get_prefix_route() are not

susceptible to this bug:

1. addrconf_prefix_rcv(): Requests a route with the 'RTF_ADDRCONF |

RTF_PREFIX_RT' flags which are not set on fib6_null_entry.

2. modify_prefix_route(): Fixed by commit a747e02430df ("ipv6: avoid

possible NULL deref in modify_prefix_route()").

3. __ipv6_ifa_notify(): Calls ip6_del_rt() which specifically checks for

fib6_null_entry and returns an error.

[1]

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP KASAN

KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]

[...]

Call Trace:

<TASK>

__kasan_check_byte (mm/kasan/common.c:573)

lock_acquire.part.0 (kernel/locking/lockdep.c:5842 (discriminator 1))

_raw_spin_lock_bh (kernel/locking/spinlock.c:182 (discriminator 1))

cleanup_prefix_route (net/ipv6/addrconf.c:1280)

ipv6_del_addr (net/ipv6/addrconf.c:1342)

inet6_addr_del.isra.0 (net/ipv6/addrconf.c:3119)

inet6_rtm_deladdr (net/ipv6/addrconf.c:4812)

rtnetlink_rcv_msg (net/core/rtnetlink.c:6997)

netlink_rcv_skb (net/netlink/af_netlink.c:2555)

netlink_unicast (net/netlink/af_netlink.c:1344)

netlink_sendmsg (net/netlink/af_netlink.c:1899)

__sock_sendmsg (net/socket.c:802 (discriminator 4))

____sys_sendmsg (net/socket.c:2698)

___sys_sendmsg (net/socket.c:2752)

__sys_sendmsg (net/socket.c:2784)

do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)

entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)