Linux Ethernet Bridging - Sep 2021 - [Bridge] [syzbot] KASAN: slab-out-of-bounds Read in add_del_if

On 03/09/2021 12:03, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    3bdc70669eb2 Merge branch 'devlink-register'
That is an older commit, before my ioctl fixes. I think this issue has been
already fixed by my patch-set:
 commit d15040a33883
 Merge: 4167a960574f 9384eacd80f3
 Author: David S. Miller <davem at davemloft.net>
 Date:   Thu Aug 5 11:36:59 2021 +0100

    Merge branch 'bridge-ioctl-fixes'
    
    Nikolay Aleksandrov says:
    
    ===================    net: bridge: fix recent ioctl changes
    
    These are three fixes for the recent bridge removal of ndo_do_ioctl
    done by commit ad2f99aedf8f ("net: bridge: move bridge ioctls out of
    .ndo_do_ioctl"). Patch 01 fixes a deadlock of the new bridge ioctl
    hook lock and rtnl by taking a netdev reference and always taking the
    bridge ioctl lock first then rtnl from within the bridge hook.
    Patch 02 fixes old_deviceless() bridge calls device name argument, and
    patch 03 checks in dev_ifsioc()'s SIOCBRADD/DELIF cases if the netdevice
is
    actually a bridge before interpreting its private ptr as net_bridge.
    
    Patch 01 was tested by running old bridge-utils commands with lockdep
    enabled. Patch 02 was tested again by using bridge-utils and using the
    respective ioctl calls on a "up" bridge device. Patch 03 was
tested by
    using the addif ioctl on a non-bridge device (e.g. loopback).

> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=147a8072300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=914a8107c0ffdc14
> dashboard link:
https://syzkaller.appspot.com/bug?extid=24b98616278c31afc800
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils
for Debian) 2.35.1
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13f4ccc9d00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15b054f4300000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the
commit:
> Reported-by: syzbot+24b98616278c31afc800 at syzkaller.appspotmail.com
> 
> =================================================================> BUG:
KASAN: slab-out-of-bounds in add_del_if+0x13a/0x140 net/bridge/br_ioctl.c:85
> Read of size 8 at addr ffff888019118c88 by task syz-executor790/8443
> 
[snip]
> ---
> This report is generated by a bot. It may contain errors.
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> 
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> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches
> 
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
d15040a33883

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any
issue:

Reported-and-tested-by: syzbot+24b98616278c31afc800 at syzkaller.appspotmail.com

Tested on:

commit:         d15040a3 Merge branch 'bridge-ioctl-fixes'
git tree:      
git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
kernel config:  https://syzkaller.appspot.com/x/.config?x=aba0c23f8230e048
dashboard link: https://syzkaller.appspot.com/bug?extid=24b98616278c31afc800
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for
Debian) 2.35.1

Note: testing is done by a robot and is best-effort only.

On 03/09/2021 14:42, syzbot wrote:
> Hello,
> 
> syzbot has tested the proposed patch and the reproducer did not trigger any
issue:
> 
> Reported-and-tested-by: syzbot+24b98616278c31afc800 at
syzkaller.appspotmail.com
> 
> Tested on:
> 
> commit:         d15040a3 Merge branch 'bridge-ioctl-fixes'
> git tree:      
git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
> kernel config:  https://syzkaller.appspot.com/x/.config?x=aba0c23f8230e048
> dashboard link:
https://syzkaller.appspot.com/bug?extid=24b98616278c31afc800
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils
for Debian) 2.35.1
> 
> Note: testing is done by a robot and is best-effort only.
> 
#syz fix: net: core: don't call SIOCBRADD/DELIF for non-bridge devices