Re: [PATCH v2 net] net: ping6: Fix memleak in ipv6_renew_options().

[David Ahern <dsahern@kernel.org>]

On 7/27/22 7:22 PM, Kuniyuki Iwashima wrote:
> When we close ping6 sockets, some resources are left unfreed because
> pingv6_prot is missing sk->sk_prot->destroy().  As reported by
> syzbot [0], just three syscalls leak 96 bytes and easily cause OOM.
> 
>     struct ipv6_sr_hdr *hdr;
>     char data[24] = {0};
>     int fd;
> 
>     hdr = (struct ipv6_sr_hdr *)data;
>     hdr->hdrlen = 2;
>     hdr->type = IPV6_SRCRT_TYPE_4;
> 
>     fd = socket(AF_INET6, SOCK_DGRAM, NEXTHDR_ICMP);
>     setsockopt(fd, IPPROTO_IPV6, IPV6_RTHDR, data, 24);
>     close(fd);
> 
> To fix memory leaks, let's add a destroy function.
> 
> Note the socket() syscall checks if the GID is within the range of
> net.ipv4.ping_group_range.  The default value is [1, 0] so that no
> GID meets the condition (1 <= GID <= 0).  Thus, the local DoS does
> not succeed until we change the default value.  However, at least
> Ubuntu/Fedora/RHEL loosen it.
> 
>     $ cat /usr/lib/sysctl.d/50-default.conf
>     ...
>     -net.ipv4.ping_group_range = 0 2147483647
> 
> Also, there could be another path reported with these options, and
> some of them require CAP_NET_RAW.
> 
>   setsockopt
>       IPV6_ADDRFORM (inet6_sk(sk)->pktoptions)
>       IPV6_RECVPATHMTU (inet6_sk(sk)->rxpmtu)
>       IPV6_HOPOPTS (inet6_sk(sk)->opt)
>       IPV6_RTHDRDSTOPTS (inet6_sk(sk)->opt)
>       IPV6_RTHDR (inet6_sk(sk)->opt)
>       IPV6_DSTOPTS (inet6_sk(sk)->opt)
>       IPV6_2292PKTOPTIONS (inet6_sk(sk)->opt)
> 
>   getsockopt
>       IPV6_FLOWLABEL_MGR (inet6_sk(sk)->ipv6_fl_list)
> 
> For the record, I left a different splat with syzbot's one.
> 
>   unreferenced object 0xffff888006270c60 (size 96):
>     comm "repro2", pid 231, jiffies 4294696626 (age 13.118s)
>     hex dump (first 32 bytes):
>       01 00 00 00 44 00 00 00 00 00 00 00 00 00 00 00  ....D...........
>       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     backtrace:
>       [<00000000f6bc7ea9>] sock_kmalloc (net/core/sock.c:2564 net/core/sock.c:2554)
>       [<000000006d699550>] do_ipv6_setsockopt.constprop.0 (net/ipv6/ipv6_sockglue.c:715)
>       [<00000000c3c3b1f5>] ipv6_setsockopt (net/ipv6/ipv6_sockglue.c:1024)
>       [<000000007096a025>] __sys_setsockopt (net/socket.c:2254)
>       [<000000003a8ff47b>] __x64_sys_setsockopt (net/socket.c:2265 net/socket.c:2262 net/socket.c:2262)
>       [<000000007c409dcb>] do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80)
>       [<00000000e939c4a9>] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)
> 
> [0]: https://syzkaller.appspot.com/bug?extid=a8430774139ec3ab7176
> 
> Fixes: 6d0bfe226116 ("net: ipv6: Add IPv6 support to the ping socket.")
> Reported-by: syzbot+a8430774139ec3ab7176@syzkaller.appspotmail.com
> Reported-by: Ayushman Dutta <ayudutta@amazon.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> ---
> v2:
>   - Remove ip6_flush_pending_frames() (Jakub Kicinski)
> 
> v1: offlist
> ---
>  net/ipv6/ping.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>