Date: Fri, 22 Sep 2023 00:15:27 +0100
From: Dmitry Safonov <dima@...sta.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: bpf@...r.kernel.org, davem@...emloft.net, dsahern@...nel.org,
 kuba@...nel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 pabeni@...hat.com, syzkaller-bugs@...glegroups.com,
 syzbot <syzbot+68662811b3d5f6695bcb@...kaller.appspotmail.com>,
 Catalin Marinas <catalin.marinas@....com>
Subject: Re: [syzbot] [net?] memory leak in tcp_md5_do_add

Hi Eric,

On 9/21/23 18:01, Dmitry Safonov wrote:
> On 9/21/23 17:59, Eric Dumazet wrote:
>> On Thu, Sep 21, 2023 at 6:56 PM syzbot
>> <syzbot+68662811b3d5f6695bcb@...kaller.appspotmail.com> wrote:
>>>
>>> Hello,
>>>
>>> syzbot found the following issue on:
>>>
>>> HEAD commit:    ee3f96b16468 Merge tag 'nfsd-6.3-1' of git://git.kernel.or..
>>> git tree:       upstream
>>> console output: https://syzkaller.appspot.com/x/log.txt?x=1312bba8c80000
>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=f5733ca1757172ad
>>> dashboard link: https://syzkaller.appspot.com/bug?extid=68662811b3d5f6695bcb
>>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=105393a8c80000
>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1113917f480000
>>>
>>> Downloadable assets:
>>> disk image: https://storage.googleapis.com/syzbot-assets/29e7966ab711/disk-ee3f96b1.raw.xz
>>> vmlinux: https://storage.googleapis.com/syzbot-assets/ae21b8e855de/vmlinux-ee3f96b1.xz
>>> kernel image: https://storage.googleapis.com/syzbot-assets/803ee0425ad6/bzImage-ee3f96b1.xz
>>>
>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>> Reported-by: syzbot+68662811b3d5f6695bcb@...kaller.appspotmail.com
>>>
>>> executing program
>>> BUG: memory leak
>>> unreferenced object 0xffff88810a86f7a0 (size 32):
>>>   comm "syz-executor325", pid 5099, jiffies 4294978342 (age 119.240s)
>>>   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:
>>>     [<ffffffff81533d64>] kmalloc_trace+0x24/0x90 mm/slab_common.c:1061
>>>     [<ffffffff840edaa0>] kmalloc include/linux/slab.h:580 [inline]
>>>     [<ffffffff840edaa0>] tcp_md5sig_info_add net/ipv4/tcp_ipv4.c:1169 [inline]
>>>     [<ffffffff840edaa0>] tcp_md5_do_add+0xa0/0x150 net/ipv4/tcp_ipv4.c:1240
>>>     [<ffffffff84262c73>] tcp_v6_parse_md5_keys+0x253/0x4a0 net/ipv6/tcp_ipv6.c:671
>>>     [<ffffffff840c720e>] do_tcp_setsockopt+0x40e/0x1360 net/ipv4/tcp.c:3720
>>>     [<ffffffff840c81fb>] tcp_setsockopt+0x9b/0xa0 net/ipv4/tcp.c:3806
>>>     [<ffffffff83d72a8b>] __sys_setsockopt+0x1ab/0x330 net/socket.c:2274
>>>     [<ffffffff83d72c36>] __do_sys_setsockopt net/socket.c:2285 [inline]
>>>     [<ffffffff83d72c36>] __se_sys_setsockopt net/socket.c:2282 [inline]
>>>     [<ffffffff83d72c36>] __x64_sys_setsockopt+0x26/0x30 net/socket.c:2282
>>>     [<ffffffff849ad699>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>>     [<ffffffff849ad699>] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>>>     [<ffffffff84a0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>>>
>>> BUG: memory leak
>>> unreferenced object 0xffff88811225ccc0 (size 192):
>>>   comm "syz-executor325", pid 5099, jiffies 4294978342 (age 119.240s)
>>>   hex dump (first 32 bytes):
>>>     00 00 00 00 00 00 00 00 22 01 00 00 00 00 ad de  ........".......
>>>     22 0a 80 00 fe 80 00 00 00 00 00 00 00 00 00 00  "...............
>>>   backtrace:
>>>     [<ffffffff8153444a>] __do_kmalloc_node mm/slab_common.c:966 [inline]
>>>     [<ffffffff8153444a>] __kmalloc+0x4a/0x120 mm/slab_common.c:980
>>>     [<ffffffff83d75c15>] kmalloc include/linux/slab.h:584 [inline]
>>>     [<ffffffff83d75c15>] sock_kmalloc net/core/sock.c:2635 [inline]
>>>     [<ffffffff83d75c15>] sock_kmalloc+0x65/0xa0 net/core/sock.c:2624
>>>     [<ffffffff840eb9bb>] __tcp_md5_do_add+0xcb/0x300 net/ipv4/tcp_ipv4.c:1212
>>>     [<ffffffff840eda67>] tcp_md5_do_add+0x67/0x150 net/ipv4/tcp_ipv4.c:1253
>>>     [<ffffffff84262c73>] tcp_v6_parse_md5_keys+0x253/0x4a0 net/ipv6/tcp_ipv6.c:671
>>>     [<ffffffff840c720e>] do_tcp_setsockopt+0x40e/0x1360 net/ipv4/tcp.c:3720
>>>     [<ffffffff840c81fb>] tcp_setsockopt+0x9b/0xa0 net/ipv4/tcp.c:3806
>>>     [<ffffffff83d72a8b>] __sys_setsockopt+0x1ab/0x330 net/socket.c:2274
>>>     [<ffffffff83d72c36>] __do_sys_setsockopt net/socket.c:2285 [inline]
>>>     [<ffffffff83d72c36>] __se_sys_setsockopt net/socket.c:2282 [inline]
>>>     [<ffffffff83d72c36>] __x64_sys_setsockopt+0x26/0x30 net/socket.c:2282
>>>     [<ffffffff849ad699>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>>     [<ffffffff849ad699>] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>>>     [<ffffffff84a0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>>>
>>>
>>>
>>> ---
>>> This report is generated by a bot. It may contain errors.
>>> See https://goo.gl/tpsmEJ for more information about syzbot.
>>> syzbot engineers can be reached at syzkaller@...glegroups.com.
>>>
>>> syzbot will keep track of this issue. See:
>>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>>>
>>> If the bug is already fixed, let syzbot know by replying with:
>>> #syz fix: exact-commit-title
>>>
>>> If you want syzbot to run the reproducer, reply with:
>>> #syz test: git://repo/address.git branch-or-commit-hash
>>> If you attach or paste a git patch, syzbot will apply it before testing.
>>>
>>> If you want to overwrite bug's subsystems, reply with:
>>> #syz set subsystems: new-subsystem
>>> (See the list of subsystem names on the web dashboard)
>>>
>>> If the bug is a duplicate of another bug, reply with:
>>> #syz dup: exact-subject-of-another-report
>>>
>>> If you want to undo deduplication, reply with:
>>> #syz undup
>>
>> Dmitry, please take a look at this bug, we need to fix it before your
>> patch series.
> 
> Sure, seems reasonable to me to fix before merging something on top.

It seems to me that it's related to a race between RCU grace period and
kmemleak scan period. There seems to be a patch [1] that likely fixes
that, albeit I couldn't verify it as all my attempts to reproduce syzbot
issue produced only unrelated to TCP-MD5 log:

> [  263.201211] kmemleak: unreferenced object 0xffff9ceb047d9948 (size 192):
> [  263.201781] kmemleak:   comm "ip", pid 730, jiffies 4294937874 (age 257.270s)
> [  263.202460] kmemleak:   hex dump (first 32 bytes):
> [  263.202921] kmemleak:     00 c8 e9 01 eb 9c ff ff e0 00 00 01 00 00 00 00  ................
> [  263.203700] kmemleak:     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> [  263.204484] kmemleak:   backtrace:
> [  263.204814] kmemleak:     [<ffffffff830a2946>] kmalloc_trace+0x26/0x90
> [  263.205440] kmemleak:     [<ffffffff837e8310>] ____ip_mc_inc_group+0xa0/0x240
> [  263.206134] kmemleak:     [<ffffffff837e9a9b>] ip_mc_up+0x4b/0xb0
> [  263.206725] kmemleak:     [<ffffffff837e28fb>] inetdev_event+0xbb/0x5c0
> [  263.207358] kmemleak:     [<ffffffff82f3caf6>] notifier_call_chain+0x56/0xc0
> [  263.208070] kmemleak:     [<ffffffff836f1818>] __dev_notify_flags+0x58/0xf0
> [  263.208784] kmemleak:     [<ffffffff836f2210>] dev_change_flags+0x50/0x60
> [  263.209471] kmemleak:     [<ffffffff837e1718>] devinet_ioctl+0x378/0x770
> [  263.210152] kmemleak:     [<ffffffff837e34a7>] inet_ioctl+0x187/0x1d0
> [  263.210805] kmemleak:     [<ffffffff836c40ed>] sock_do_ioctl+0x3d/0x100
> [  263.211482] kmemleak:     [<ffffffff836c4293>] sock_ioctl+0xe3/0x2b0
> [  263.212131] kmemleak:     [<ffffffff8313cbec>] __x64_sys_ioctl+0x8c/0xc0
> [  263.212789] kmemleak:     [<ffffffff83a2ad75>] do_syscall_64+0x35/0x80
> [  263.213438] kmemleak:     [<ffffffff83c0006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
> [  263.214283] kmemleak: unreferenced object 0xffff9ceb03ad5400 (size 512):
> [  263.214982] kmemleak:   comm "ip", pid 730, jiffies 4294937874 (age 257.290s)
> [  263.215728] kmemleak:   hex dump (first 32 bytes):
> [  263.216231] kmemleak:     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01  ................
> [  263.217106] kmemleak:     80 00 00 00 00 00 00 00 ff ff ff ff ff ff ff ff  ................
> [  263.218041] kmemleak:   backtrace:
> [  263.218438] kmemleak:     [<ffffffff830a2946>] kmalloc_trace+0x26/0x90
> [  263.219181] kmemleak:     [<ffffffff8384b90b>] ipv6_add_addr+0x13b/0x6c0
> [  263.219931] kmemleak:     [<ffffffff8384d4b5>] add_addr+0x75/0x150
> [  263.220627] kmemleak:     [<ffffffff8385357d>] addrconf_notify+0x53d/0x730
> [  263.221377] kmemleak:     [<ffffffff82f3caf6>] notifier_call_chain+0x56/0xc0
> [  263.222104] kmemleak:     [<ffffffff836f1818>] __dev_notify_flags+0x58/0xf0
> [  263.222844] kmemleak:     [<ffffffff836f2210>] dev_change_flags+0x50/0x60
> [  263.223581] kmemleak:     [<ffffffff837e1718>] devinet_ioctl+0x378/0x770
> [  263.224293] kmemleak:     [<ffffffff837e34a7>] inet_ioctl+0x187/0x1d0
> [  263.224961] kmemleak:     [<ffffffff836c40ed>] sock_do_ioctl+0x3d/0x100
> [  263.225660] kmemleak:     [<ffffffff836c4293>] sock_ioctl+0xe3/0x2b0
> [  263.226331] kmemleak:     [<ffffffff8313cbec>] __x64_sys_ioctl+0x8c/0xc0
> [  263.227039] kmemleak:     [<ffffffff83a2ad75>] do_syscall_64+0x35/0x80
> [  263.227747] kmemleak:     [<ffffffff83c0006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
> [  263.228708] kmemleak: 2 new suspected memory leaks (see /sys/kernel/debug/kmemleak)

This seems to be quite the same issue: inet6_ifa_finish_destroy()
destroys inet6_ifaddr with kfree_rcu().

[1]
https://lore.kernel.org/linux-mm/ZQA064908T5nngcc@arm.com/T/#ma4a68fdc44793e2594c9e7cadefa8ea40da5807d

Thanks,
            Dmitry

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