netdev - Re: memory leak in ctnetlink

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Message-ID: <20200609223802.GB29165@salvia>
Date:   Wed, 10 Jun 2020 00:38:02 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     syzbot <syzbot+b005af2cfb0411e617de@...kaller.appspotmail.com>
Cc:     coreteam@...filter.org, davem@...emloft.net, fw@...len.de,
        kadlec@...filter.org, kuba@...nel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: memory leak in ctnetlink_start

On Tue, Jun 09, 2020 at 02:58:12PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=128a9df2100000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9a1aa05456dfd557
> dashboard link: https://syzkaller.appspot.com/bug?extid=b005af2cfb0411e617de
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17304a96100000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=168a9df2100000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+b005af2cfb0411e617de@...kaller.appspotmail.com
> 
> executing program
> executing program
> executing program
> BUG: memory leak
> unreferenced object 0xffff88811c797900 (size 128):
>   comm "syz-executor256", pid 6458, jiffies 4294947022 (age 13.050s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<000000004276332a>] kmalloc include/linux/slab.h:555 [inline]
>     [<000000004276332a>] kzalloc include/linux/slab.h:669 [inline]
>     [<000000004276332a>] ctnetlink_alloc_filter+0x3a/0x2a0 net/netfilter/nf_conntrack_netlink.c:924
>     [<000000000047e6fb>] ctnetlink_start+0x3a/0x80 net/netfilter/nf_conntrack_netlink.c:998
>     [<00000000a431a924>] __netlink_dump_start+0x1a3/0x2e0 net/netlink/af_netlink.c:2343
>     [<0000000016b073fa>] netlink_dump_start include/linux/netlink.h:246 [inline]
>     [<0000000016b073fa>] ctnetlink_get_conntrack+0x26d/0x2f0 net/netfilter/nf_conntrack_netlink.c:1611
>     [<00000000d311138b>] nfnetlink_rcv_msg+0x32f/0x370 net/netfilter/nfnetlink.c:229
>     [<0000000008feca87>] netlink_rcv_skb+0x5a/0x180 net/netlink/af_netlink.c:2469
>     [<0000000088caad78>] nfnetlink_rcv+0x83/0x1b0 net/netfilter/nfnetlink.c:563
>     [<0000000052160488>] netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
>     [<0000000052160488>] netlink_unicast+0x20a/0x2f0 net/netlink/af_netlink.c:1329
>     [<00000000ee36d991>] netlink_sendmsg+0x2b5/0x560 net/netlink/af_netlink.c:1918
>     [<00000000dee2cafe>] sock_sendmsg_nosec net/socket.c:652 [inline]
>     [<00000000dee2cafe>] sock_sendmsg+0x4c/0x60 net/socket.c:672
>     [<00000000b0b655cb>] ____sys_sendmsg+0x2c4/0x2f0 net/socket.c:2352
>     [<000000005bba2f8d>] ___sys_sendmsg+0x8a/0xd0 net/socket.c:2406
>     [<0000000060ac6563>] __sys_sendmsg+0x77/0xe0 net/socket.c:2439
>     [<000000002f7b34b0>] do_syscall_64+0x6e/0x220 arch/x86/entry/common.c:295
>     [<00000000941009bb>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Hm, filter is not released in the error path.

View attachment "z.patch" of type "text/x-diff" (3952 bytes)