Re: memory leak in sctp_v4_create_accept_sk

[Xin Long]

On Mon, Jun 24, 2019 at 3:28 PM syzbot
<syzbot+afabda3890cc2f765041@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    abf02e29 Merge tag 'pm-5.2-rc6' of git://git.kernel.org/pu..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13470eb2a00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=56f1da14935c3cce
> dashboard link: https://syzkaller.appspot.com/bug?extid=afabda3890cc2f765041
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15100a91a00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10c46026a00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+afabda3890cc2f765041@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ffffffffda RBX: 00000000006fbc38 RCX: 0000000000446a79
> BUG: memory leak
> unreferenced object 0xffff888118137680 (size 1352):
>    comm "syz-executor360", pid 7164, jiffies 4294941839 (age 13.960s)
>    hex dump (first 32 bytes):
>      ac 14 ff aa 0a 80 01 1a 00 00 00 00 00 00 00 00  ................
>      02 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00  ...@............
>    backtrace:
>      [<000000006c358063>] kmemleak_alloc_recursive
> include/linux/kmemleak.h:43 [inline]
>      [<000000006c358063>] slab_post_alloc_hook mm/slab.h:439 [inline]
>      [<000000006c358063>] slab_alloc mm/slab.c:3326 [inline]
>      [<000000006c358063>] kmem_cache_alloc+0x134/0x270 mm/slab.c:3488
>      [<00000000f2fb26e7>] sk_prot_alloc+0x41/0x170 net/core/sock.c:1596
>      [<000000003c036edc>] sk_alloc+0x35/0x2f0 net/core/sock.c:1656
>      [<00000000c25725a4>] sctp_v4_create_accept_sk+0x32/0xb0
> net/sctp/protocol.c:556
>      [<0000000049bd7e55>] sctp_accept+0x1df/0x290 net/sctp/socket.c:4913
>      [<00000000d287a63e>] inet_accept+0x4e/0x1d0 net/ipv4/af_inet.c:734
>      [<00000000acb0fc20>] __sys_accept4+0x12a/0x280 net/socket.c:1760
>      [<00000000bbdaf60b>] __do_sys_accept4 net/socket.c:1795 [inline]
>      [<00000000bbdaf60b>] __se_sys_accept4 net/socket.c:1792 [inline]
>      [<00000000bbdaf60b>] __x64_sys_accept4+0x22/0x30 net/socket.c:1792
>      [<000000006da547ee>] do_syscall_64+0x76/0x1a0
> arch/x86/entry/common.c:301
>      [<00000000025f5c93>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
The same issue as "memory leak in sctp_v6_create_accept_sk" one.
Fix:

diff --git a/net/sctp/endpointola.c b/net/sctp/endpointola.c
index e358437..69cebb2 100644
--- a/net/sctp/endpointola.c
+++ b/net/sctp/endpointola.c
@@ -118,10 +118,6 @@ static struct sctp_endpoint
*sctp_endpoint_init(struct sctp_endpoint *ep,
        /* Initialize the bind addr area */
        sctp_bind_addr_init(&ep->base.bind_addr, 0);

-       /* Remember who we are attached to.  */
-       ep->base.sk = sk;
-       sock_hold(ep->base.sk);
-
        /* Create the lists of associations.  */
        INIT_LIST_HEAD(&ep->asocs);

@@ -154,6 +150,10 @@ static struct sctp_endpoint
*sctp_endpoint_init(struct sctp_endpoint *ep,
        ep->prsctp_enable = net->sctp.prsctp_enable;
        ep->reconf_enable = net->sctp.reconf_enable;

+       /* Remember who we are attached to.  */
+       ep->base.sk = sk;
+       sock_hold(ep->base.sk);
+
        return ep;

 nomem_shkey:

>
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