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

Message-ID: <CANn89iKTA7YN=cZebH5NaNV41LuGKk5GfcZTf3yyrcJJE8EBpQ@mail.gmail.com>
Date: Mon, 2 Dec 2024 10:11:55 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Paolo Abeni <pabeni@...hat.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 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);
}