Re: [PATCH 4.14 1/1] tcp/udp: Fix memory leak in ipv6_renew_options().

[Greg KH <greg@kroah.com>]

On Thu, Nov 24, 2022 at 11:42:26AM +0200, Ovidiu Panait wrote:
> From: Kuniyuki Iwashima <kuniyu@amazon.com>
> 
> commit 3c52c6bb831f6335c176a0fc7214e26f43adbd11 upstream.
> 
> syzbot reported a memory leak [0] related to IPV6_ADDRFORM.
> 
> The scenario is that while one thread is converting an IPv6 socket into
> IPv4 with IPV6_ADDRFORM, another thread calls do_ipv6_setsockopt() and
> allocates memory to inet6_sk(sk)->XXX after conversion.
> 
> Then, the converted sk with (tcp|udp)_prot never frees the IPv6 resources,
> which inet6_destroy_sock() should have cleaned up.
> 
> setsockopt(IPV6_ADDRFORM)                 setsockopt(IPV6_DSTOPTS)
> +-----------------------+                 +----------------------+
> - do_ipv6_setsockopt(sk, ...)
>   - sockopt_lock_sock(sk)                 - do_ipv6_setsockopt(sk, ...)
>     - lock_sock(sk)                         ^._ called via tcpv6_prot
>   - WRITE_ONCE(sk->sk_prot, &tcp_prot)          before WRITE_ONCE()
>   - xchg(&np->opt, NULL)
>   - txopt_put(opt)
>   - sockopt_release_sock(sk)
>     - release_sock(sk)                      - sockopt_lock_sock(sk)
>                                               - lock_sock(sk)
>                                             - ipv6_set_opt_hdr(sk, ...)
>                                               - ipv6_update_options(sk, opt)
>                                                 - xchg(&inet6_sk(sk)->opt, opt)
>                                                   ^._ opt is never freed.
> 
>                                             - sockopt_release_sock(sk)
>                                               - release_sock(sk)
> 
> Since IPV6_DSTOPTS allocates options under lock_sock(), we can avoid this
> memory leak by testing whether sk_family is changed by IPV6_ADDRFORM after
> acquiring the lock.
> 
> This issue exists from the initial commit between IPV6_ADDRFORM and
> IPV6_PKTOPTIONS.
> 
> [0]:
> BUG: memory leak
> unreferenced object 0xffff888009ab9f80 (size 96):
>   comm "syz-executor583", pid 328, jiffies 4294916198 (age 13.034s)
>   hex dump (first 32 bytes):
>     01 00 00 00 48 00 00 00 08 00 00 00 00 00 00 00  ....H...........
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<000000002ee98ae1>] kmalloc include/linux/slab.h:605 [inline]
>     [<000000002ee98ae1>] sock_kmalloc+0xb3/0x100 net/core/sock.c:2566
>     [<0000000065d7b698>] ipv6_renew_options+0x21e/0x10b0 net/ipv6/exthdrs.c:1318
>     [<00000000a8c756d7>] ipv6_set_opt_hdr net/ipv6/ipv6_sockglue.c:354 [inline]
>     [<00000000a8c756d7>] do_ipv6_setsockopt.constprop.0+0x28b7/0x4350 net/ipv6/ipv6_sockglue.c:668
>     [<000000002854d204>] ipv6_setsockopt+0xdf/0x190 net/ipv6/ipv6_sockglue.c:1021
>     [<00000000e69fdcf8>] tcp_setsockopt+0x13b/0x2620 net/ipv4/tcp.c:3789
>     [<0000000090da4b9b>] __sys_setsockopt+0x239/0x620 net/socket.c:2252
>     [<00000000b10d192f>] __do_sys_setsockopt net/socket.c:2263 [inline]
>     [<00000000b10d192f>] __se_sys_setsockopt net/socket.c:2260 [inline]
>     [<00000000b10d192f>] __x64_sys_setsockopt+0xbe/0x160 net/socket.c:2260
>     [<000000000a80d7aa>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>     [<000000000a80d7aa>] do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80
>     [<000000004562b5c6>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
> ---
>  net/ipv6/ipv6_sockglue.c | 7 +++++++
>  1 file changed, 7 insertions(+)

All now queued up, thanks.

greg k-h