From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
To: syzbot <syzbot+0e4699d000d8b874d8dc@syzkaller.appspotmail.com>
Cc: davem@davemloft.net, kuba@kernel.org,
linux-kernel@vger.kernel.org, linux-sctp@vger.kernel.org,
netdev@vger.kernel.org, nhorman@tuxdriver.com,
syzkaller-bugs@googlegroups.com, vyasevich@gmail.com, hch@lst.de
Subject: Re: KASAN: slab-out-of-bounds Write in sctp_setsockopt
Date: Wed, 22 Jul 2020 19:02:50 +0000 [thread overview]
Message-ID: <20200722190250.GE3307@localhost.localdomain> (raw)
In-Reply-To: <0000000000003b813605ab0bd243@google.com>
On Wed, Jul 22, 2020 at 11:22:23AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 4f1b4da5 Merge branch 'net-atlantic-various-features'
> git tree: net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x\x14b3a040900000
> kernel config: https://syzkaller.appspot.com/x/.config?x+7b67c0c1819c87
> dashboard link: https://syzkaller.appspot.com/bug?extid\x0e4699d000d8b874d8dc
> compiler: gcc (GCC) 10.1.0-syz 20200507
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x\x14c93358900000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x\x14ab61f0900000
The syz repo has:
setsockopt$inet_sctp6_SCTP_MAX_BURST(r0, 0x84, 0x10, &(0x7f0000000100)=@assoc_value, 0x8)
^^^^^^^^^^^^^^ ^^^^
#define SCTP_DELAYED_ACK_TIME 16
#define SCTP_DELAYED_ACK SCTP_DELAYED_ACK_TIME
#define SCTP_DELAYED_SACK SCTP_DELAYED_ACK_TIME
#define SCTP_MAX_BURST 20 /* Set/Get max burst */
C repro has:
syscall(__NR_setsockopt, r[0], 0x84, 0x10, 0x20000100ul, 8ul);
^^^^
So I'm wondering, what was the real intention of the call?
Anyhow, the issue is real, introduced by ebb25defdc17 ("sctp: pass a
kernel pointer to sctp_setsockopt_delayed_ack"). It used to use a
local storage bigger than the data provided by the user and used
one struct to read another's content on top of it. Quite masked.
I'll cook a fix.
Marcelo
prev parent reply other threads:[~2020-07-22 19:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 18:22 KASAN: slab-out-of-bounds Write in sctp_setsockopt syzbot
2020-07-22 19:02 ` Marcelo Ricardo Leitner [this message]
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