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: Meena Shanmugam meenashanmugam@google.com --- net/ipv6/ipv6_sockglue.c | 7 +++++++ 1 file changed, 7 insertions(+)

diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c index 8a1c78f38508..b24e0e5d55f9 100644 --- a/net/ipv6/ipv6_sockglue.c +++ b/net/ipv6/ipv6_sockglue.c @@ -417,6 +417,12 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname, rtnl_lock(); lock_sock(sk);

+ /* Another thread has converted the socket into IPv4 with + * IPV6_ADDRFORM concurrently. + */ + if (unlikely(sk->sk_family != AF_INET6)) + goto unlock; + switch (optname) {

case IPV6_ADDRFORM: @@ -976,6 +982,7 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname, break; }

+unlock: release_sock(sk); if (needs_rtnl) rtnl_unlock();