linux-kernel - Re: memory leak in sctp_stream_init

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Message-ID: <20200417133110.GA2688@localhost.localdomain>
Date:   Fri, 17 Apr 2020 10:31:10 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Hillf Danton <hdanton@...a.com>
Cc:     syzbot <syzbot+96e916d6f6f7617bc9fc@...kaller.appspotmail.com>,
        davem@...emloft.net, kuba@...nel.org, linux-kernel@...r.kernel.org,
        linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        nhorman@...driver.com, syzkaller-bugs@...glegroups.com,
        vyasevich@...il.com
Subject: Re: memory leak in sctp_stream_init_ext (2)

On Fri, Apr 17, 2020 at 04:32:24PM +0800, Hillf Danton wrote:
> 
> On Thu, 16 Apr 2020 20:45:10 -0700
> > syzbot found the following crash on:
> > 
> > HEAD commit:    00086336 Merge tag 'efi-urgent-2020-04-15' of git://git.ke..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=12996107e00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=efff978b972fb2c
> > dashboard link: https://syzkaller.appspot.com/bug?extid=96e916d6f6f7617bc9fc
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=137ddf3fe00000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+96e916d6f6f7617bc9fc@...kaller.appspotmail.com
> > 
> > BUG: memory leak
> > unreferenced object 0xffff888103ba4580 (size 96):
> >   comm "syz-executor.1", pid 8335, jiffies 4294953411 (age 14.410s)
> >   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:
> >     [<00000000b06f3e80>] kmalloc include/linux/slab.h:555 [inline]
> >     [<00000000b06f3e80>] kzalloc include/linux/slab.h:669 [inline]
> >     [<00000000b06f3e80>] sctp_stream_init_ext+0x28/0xe0 net/sctp/stream.c:162
> >     [<00000000aff2ecba>] sctp_sendmsg_to_asoc+0x9af/0xab0 net/sctp/socket.c:1811
> >     [<00000000d5d5eb76>] sctp_sendmsg+0x2a6/0xc60 net/sctp/socket.c:2031
> >     [<0000000023cdbfa3>] inet_sendmsg+0x39/0x60 net/ipv4/af_inet.c:807
> >     [<00000000885878ef>] sock_sendmsg_nosec net/socket.c:652 [inline]
> >     [<00000000885878ef>] sock_sendmsg+0x4c/0x60 net/socket.c:672
> >     [<0000000009d727e5>] __sys_sendto+0x11d/0x1c0 net/socket.c:2000
> >     [<0000000066974477>] __do_sys_sendto net/socket.c:2012 [inline]
> >     [<0000000066974477>] __se_sys_sendto net/socket.c:2008 [inline]
> >     [<0000000066974477>] __x64_sys_sendto+0x26/0x30 net/socket.c:2008
> >     [<00000000ecc1fea9>] do_syscall_64+0x6e/0x220 arch/x86/entry/common.c:295
> >     [<00000000605d798b>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Release ext in case of failure of initializing stream.
> 
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -145,9 +145,10 @@ in:
>  	ret = sctp_stream_alloc_in(stream, incnt, gfp);
>  	if (ret) {

Are you working on the right code? Seems you're missing
61d5d4062876 ("sctp: fix err handling of stream initialization")

Anyhow, the patch intention looks right.

>  		sched->free(stream);
> +		for (i = 0; i < stream->outcnt; i++)
> +			kfree(SCTP_SO(stream, i)->ext);
>  		genradix_free(&stream->out);
>  		stream->outcnt = 0;
> -		goto out;
>  	}
>  
>  out:
>