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Date:   Sun, 2 Jun 2019 06:51:33 -0400
From:   Neil Horman <nhorman@...driver.com>
To:     Hillf Danton <hdanton@...a.com>
Cc:     linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller@...glegroups.com,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        syzbot <syzbot+6ad9c3bd0a218a2ab41d@...kaller.appspotmail.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Xin Long <lucien.xin@...il.com>,
        Vlad Yasevich <vyasevich@...il.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH] net: sctp: fix memory leak in sctp_send_reset_streams

On Sun, Jun 02, 2019 at 11:44:29AM +0800, Hillf Danton wrote:
> 
> syzbot found the following crash on:
> 
> HEAD commit:    036e3431 Merge git://git.kernel.org/pub/scm/linux/kernel/g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=153cff12a00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8f0f63a62bb5b13c
> dashboard link: https://syzkaller.appspot.com/bug?extid=6ad9c3bd0a218a2ab41d
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12561c86a00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15b76fd8a00000
> 
> executing program
> executing program
> executing program
> executing program
> executing program
> BUG: memory leak
> unreferenced object 0xffff888123894820 (size 32):
>   comm "syz-executor045", pid 7267, jiffies 4294943559 (age 13.660s)
>   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:
>     [<00000000c7e71c69>] kmemleak_alloc_recursive
> include/linux/kmemleak.h:55 [inline]
>     [<00000000c7e71c69>] slab_post_alloc_hook mm/slab.h:439 [inline]
>     [<00000000c7e71c69>] slab_alloc mm/slab.c:3326 [inline]
>     [<00000000c7e71c69>] __do_kmalloc mm/slab.c:3658 [inline]
>     [<00000000c7e71c69>] __kmalloc+0x161/0x2c0 mm/slab.c:3669
>     [<000000003250ed8e>] kmalloc_array include/linux/slab.h:670 [inline]
>     [<000000003250ed8e>] kcalloc include/linux/slab.h:681 [inline]
>     [<000000003250ed8e>] sctp_send_reset_streams+0x1ab/0x5a0 net/sctp/stream.c:302
>     [<00000000cd899c6e>] sctp_setsockopt_reset_streams net/sctp/socket.c:4314 [inline]
>     [<00000000cd899c6e>] sctp_setsockopt net/sctp/socket.c:4765 [inline]
>     [<00000000cd899c6e>] sctp_setsockopt+0xc23/0x2bf0 net/sctp/socket.c:4608
>     [<00000000ff3a21a2>] sock_common_setsockopt+0x38/0x50 net/core/sock.c:3130
>     [<000000009eb87ae7>] __sys_setsockopt+0x98/0x120 net/socket.c:2078
>     [<00000000e0ede6ca>] __do_sys_setsockopt net/socket.c:2089 [inline]
>     [<00000000e0ede6ca>] __se_sys_setsockopt net/socket.c:2086 [inline]
>     [<00000000e0ede6ca>] __x64_sys_setsockopt+0x26/0x30 net/socket.c:2086
>     [<00000000c61155f5>] do_syscall_64+0x76/0x1a0 arch/x86/entry/common.c:301
>     [<00000000e540958c>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> 
> It was introduced in commit d570a59c5b5f ("sctp: only allow the out stream
> reset when the stream outq is empty"), in orde to check stream outqs before
> sending SCTP_STRRESET_IN_PROGRESS back to the peer of the stream. EAGAIN is
> returned, however, without the nstr_list slab released, if any outq is found
> to be non empty.
> 
> Freeing the slab in question before bailing out fixes it.
> 
> Fixes: d570a59c5b5f ("sctp: only allow the out stream reset when the stream outq is empty")
> Reported-by: syzbot <syzbot+6ad9c3bd0a218a2ab41d@...kaller.appspotmail.com>
> Reported-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> Tested-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> Cc: Xin Long <lucien.xin@...il.com>
> Cc: Neil Horman <nhorman@...driver.com>
> Cc: Vlad Yasevich <vyasevich@...il.com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Hillf Danton <hdanton@...a.com>
> ---
> net/sctp/stream.c | 1 +
> 1 file changed, 1 insertion(+)
> 
> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> index 93ed078..d3e2f03 100644
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -310,6 +310,7 @@ int sctp_send_reset_streams(struct sctp_association *asoc,
> 
> 	if (out && !sctp_stream_outq_is_empty(stream, str_nums, nstr_list)) {
> 		retval = -EAGAIN;
> +		kfree(nstr_list);
> 		goto out;
> 	}
> 
> --
> 
> 
Acked-by: Neil Horman <nhorman@...driver.com>

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