netdev - Re: [PATCH v2 net] ipmr: tune the ipmr_can_free

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] [day] [month] [year] [list]
Message-ID: <9646e7b4-d49c-48df-8b29-e21186ef89b4@redhat.com>
Date: Mon, 2 Dec 2024 10:48:59 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
 Jakub Kicinski <kuba@...nel.org>, Simon Horman <horms@...nel.org>,
 David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH v2 net] ipmr: tune the ipmr_can_free_table() checks.

On 12/2/24 10:11, Eric Dumazet wrote:
> On Mon, Dec 2, 2024 at 9:59 AM Paolo Abeni <pabeni@...hat.com> wrote:
>> Eric reported a syzkaller-triggered splat caused by recent ipmr changes:
>>
>> WARNING: CPU: 2 PID: 6041 at net/ipv6/ip6mr.c:419
>> ip6mr_free_table+0xbd/0x120 net/ipv6/ip6mr.c:419
>> Modules linked in:
>> CPU: 2 UID: 0 PID: 6041 Comm: syz-executor183 Not tainted
>> 6.12.0-syzkaller-10681-g65ae975e97d5 #0
>> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
>> 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
>> RIP: 0010:ip6mr_free_table+0xbd/0x120 net/ipv6/ip6mr.c:419
>> Code: 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c
>> 02 00 75 58 49 83 bc 24 c0 0e 00 00 00 74 09 e8 44 ef a9 f7 90 <0f> 0b
>> 90 e8 3b ef a9 f7 48 8d 7b 38 e8 12 a3 96 f7 48 89 df be 0f
>> RSP: 0018:ffffc90004267bd8 EFLAGS: 00010293
>> RAX: 0000000000000000 RBX: ffff88803c710000 RCX: ffffffff89e4d844
>> RDX: ffff88803c52c880 RSI: ffffffff89e4d87c RDI: ffff88803c578ec0
>> RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
>> R10: 0000000000000001 R11: 0000000000000001 R12: ffff88803c578000
>> R13: ffff88803c710000 R14: ffff88803c710008 R15: dead000000000100
>> FS: 00007f7a855ee6c0(0000) GS:ffff88806a800000(0000) knlGS:0000000000000000
>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 00007f7a85689938 CR3: 000000003c492000 CR4: 0000000000352ef0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>> <TASK>
>> ip6mr_rules_exit+0x176/0x2d0 net/ipv6/ip6mr.c:283
>> ip6mr_net_exit_batch+0x53/0xa0 net/ipv6/ip6mr.c:1388
>> ops_exit_list+0x128/0x180 net/core/net_namespace.c:177
>> setup_net+0x4fe/0x860 net/core/net_namespace.c:394
>> copy_net_ns+0x2b4/0x6b0 net/core/net_namespace.c:500
>> create_new_namespaces+0x3ea/0xad0 kernel/nsproxy.c:110
>> unshare_nsproxy_namespaces+0xc0/0x1f0 kernel/nsproxy.c:228
>> ksys_unshare+0x45d/0xa40 kernel/fork.c:3334
>> __do_sys_unshare kernel/fork.c:3405 [inline]
>> __se_sys_unshare kernel/fork.c:3403 [inline]
>> __x64_sys_unshare+0x31/0x40 kernel/fork.c:3403
>> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>> do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> RIP: 0033:0x7f7a856332d9
>> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 00 00 90 48 89 f8 48
>> 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
>> 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
>> RSP: 002b:00007f7a855ee238 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
>> RAX: ffffffffffffffda RBX: 00007f7a856bd308 RCX: 00007f7a856332d9
>> RDX: 00007f7a8560f8c6 RSI: 0000000000000000 RDI: 0000000062040200
>> RBP: 00007f7a856bd300 R08: 00007fff932160a7 R09: 00007f7a855ee6c0
>> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7a856bd30c
>> R13: 0000000000000000 R14: 00007fff93215fc0 R15: 00007fff932160a8
>> </TASK>
>>
>> The root cause is a network namespace creation failing after successful
>> initialization of the ipmr subsystem. Such a case is not currently
>> matched by the ipmr_can_free_table() helper.
>>
>> New namespaces are zeroed on allocation and inserted into net ns list
>> only after successful creation; when deleting an ipmr table, the list
>> next pointer can be NULL only on netns initialization failure.
>>
>> Update the ipmr_can_free_table() checks leveraging such condition.
>>
>> Reported-by: Eric Dumazet <edumazet@...gle.com>
>> Fixes: 11b6e701bce9 ("ipmr: add debug check for mr table cleanup")
>> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
>> ---
>> v1 -> v2:
>>  - move the netns init completed check in a new helper
>> ---
>>  include/net/net_namespace.h | 5 +++++
>>  net/ipv4/ipmr.c             | 2 +-
>>  net/ipv6/ip6mr.c            | 2 +-
>>  3 files changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
>> index 873c0f9fdac6..ac301c7d48a4 100644
>> --- a/include/net/net_namespace.h
>> +++ b/include/net/net_namespace.h
>> @@ -325,6 +325,11 @@ static inline int check_net(const struct net *net)
>>  #define net_drop_ns NULL
>>  #endif
>>
>> +/* Returns true if the netns initialization is completed successfully */
>> +static inline bool net_initialized(struct net *net)
>> +{
>> +       return net->list.next;
> 
> It is unclear what lock protects this read (or context it can be used)
> 
> Perhaps we could make clear no lock is needed (and add a const qual)
> 
> static inline bool net_initialized(const struct net *net)
> {
>        return READ_ONCE(net->list.next);
> }

Thanks, I will do in v3.

Paolo