netdev - Re: [PATCH v2] can: af_can: can_rcv() canfd_rcv(): Fix access of uninitialized memory or out of bounds

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <a77d525e-e174-e732-1f36-c4dace4fa532@hartkopp.net>
Date:   Tue, 25 Feb 2020 15:06:21 +0100
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        "linux-can @ vger . kernel . org" <linux-can@...r.kernel.org>
Cc:     kernel@...gutronix.de, glider@...gle.com, kuba@...nel.org,
        netdev@...r.kernel.org,
        syzbot+9bcb0c9409066696d3aa@...kaller.appspotmail.com
Subject: Re: [PATCH v2] can: af_can: can_rcv() canfd_rcv(): Fix access of
 uninitialized memory or out of bounds



On 25/02/2020 09.40, Marc Kleine-Budde wrote:
> On 2/25/20 9:39 AM, Marc Kleine-Budde wrote:
>> Syzbot found the use of uninitialzied memory when injecting non conformant
>> CANFD frames via a tun device into the kernel:
>>
>> | BUG: KMSAN: uninit-value in number+0x9f8/0x2000 lib/vsprintf.c:459
>> | CPU: 1 PID: 11897 Comm: syz-executor136 Not tainted 5.6.0-rc2-syzkaller #0
>> | Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>> | Call Trace:
>> |  __dump_stack lib/dump_stack.c:77 [inline]
>> |  dump_stack+0x1c9/0x220 lib/dump_stack.c:118
>> |  kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
>> |  __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
>> |  number+0x9f8/0x2000 lib/vsprintf.c:459
>> |  vsnprintf+0x1d85/0x31b0 lib/vsprintf.c:2640
>> |  vscnprintf+0xc2/0x180 lib/vsprintf.c:2677
>> |  vprintk_store+0xef/0x11d0 kernel/printk/printk.c:1917
>> |  vprintk_emit+0x2c0/0x860 kernel/printk/printk.c:1984
>> |  vprintk_default+0x90/0xa0 kernel/printk/printk.c:2029
>> |  vprintk_func+0x636/0x820 kernel/printk/printk_safe.c:386
>> |  printk+0x18b/0x1d3 kernel/printk/printk.c:2062
>> |  canfd_rcv+0x370/0x3a0 net/can/af_can.c:697
>> |  __netif_receive_skb_one_core net/core/dev.c:5198 [inline]
>> |  __netif_receive_skb net/core/dev.c:5312 [inline]
>> |  netif_receive_skb_internal net/core/dev.c:5402 [inline]
>> |  netif_receive_skb+0xe77/0xf20 net/core/dev.c:5461
>> |  tun_rx_batched include/linux/skbuff.h:4321 [inline]
>> |  tun_get_user+0x6aef/0x6f60 drivers/net/tun.c:1997
>> |  tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2026
>> |  call_write_iter include/linux/fs.h:1901 [inline]
>> |  new_sync_write fs/read_write.c:483 [inline]
>> |  __vfs_write+0xa5a/0xca0 fs/read_write.c:496
>> |  vfs_write+0x44a/0x8f0 fs/read_write.c:558
>> |  ksys_write+0x267/0x450 fs/read_write.c:611
>> |  __do_sys_write fs/read_write.c:623 [inline]
>> |  __se_sys_write+0x92/0xb0 fs/read_write.c:620
>> |  __x64_sys_write+0x4a/0x70 fs/read_write.c:620
>> |  do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
>> |  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>
>> In canfd_rcv() the non conformant CANFD frame (i.e. skb too short) is detected,
>> but the pr_warn_once() accesses uninitialized memory or the skb->data out of
>> bounds to print the warning message.
>>
>> This problem exists in both can_rcv() and canfd_rcv(). This patch removes the
>> access to the skb->data from the pr_warn_once() in both functions.
>>
>> Reported-by: syzbot+9bcb0c9409066696d3aa@...kaller.appspotmail.com
>> Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
>> ---
>> Hello,
>>
>> changes since RFC:
>> - print cfd->len if backed by skb, -1 otherwise
>>    (Requested by Oliver)
> 
> Doh! I have to adjust the patch description. Will do in next iteration.

Thanks Marc!

So for the next iteration:
Acked-by: Oliver Hartkopp <socketcan@...tkopp.net>

Best,
Oliver