netdev - Re: [PATCH net] net/sched: act_sample: fix NULL dereference in the data path

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Message-ID: <20180914100247.GN25110@nanopsycho>
Date:   Fri, 14 Sep 2018 12:02:47 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Davide Caratti <dcaratti@...hat.com>
Cc:     mcroce@...hat.com, Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net] net/sched: act_sample: fix NULL dereference in the
 data path

Fri, Sep 14, 2018 at 12:03:18PM CEST, dcaratti@...hat.com wrote:
>Matteo reported the following splat, testing the datapath of TC 'sample':
>
> BUG: KASAN: null-ptr-deref in tcf_sample_act+0xc4/0x310
> Read of size 8 at addr 0000000000000000 by task nc/433
>
> CPU: 0 PID: 433 Comm: nc Not tainted 4.19.0-rc3-kvm #17
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS ?-20180531_142017-buildhw-08.phx2.fedoraproject.org-1.fc28 04/01/2014
> Call Trace:
>  kasan_report.cold.6+0x6c/0x2fa
>  tcf_sample_act+0xc4/0x310
>  ? dev_hard_start_xmit+0x117/0x180
>  tcf_action_exec+0xa3/0x160
>  tcf_classify+0xdd/0x1d0
>  htb_enqueue+0x18e/0x6b0
>  ? deref_stack_reg+0x7a/0xb0
>  ? htb_delete+0x4b0/0x4b0
>  ? unwind_next_frame+0x819/0x8f0
>  ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
>  __dev_queue_xmit+0x722/0xca0
>  ? unwind_get_return_address_ptr+0x50/0x50
>  ? netdev_pick_tx+0xe0/0xe0
>  ? save_stack+0x8c/0xb0
>  ? kasan_kmalloc+0xbe/0xd0
>  ? __kmalloc_track_caller+0xe4/0x1c0
>  ? __kmalloc_reserve.isra.45+0x24/0x70
>  ? __alloc_skb+0xdd/0x2e0
>  ? sk_stream_alloc_skb+0x91/0x3b0
>  ? tcp_sendmsg_locked+0x71b/0x15a0
>  ? tcp_sendmsg+0x22/0x40
>  ? __sys_sendto+0x1b0/0x250
>  ? __x64_sys_sendto+0x6f/0x80
>  ? do_syscall_64+0x5d/0x150
>  ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
>  ? __sys_sendto+0x1b0/0x250
>  ? __x64_sys_sendto+0x6f/0x80
>  ? do_syscall_64+0x5d/0x150
>  ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
>  ip_finish_output2+0x495/0x590
>  ? ip_copy_metadata+0x2e0/0x2e0
>  ? skb_gso_validate_network_len+0x6f/0x110
>  ? ip_finish_output+0x174/0x280
>  __tcp_transmit_skb+0xb17/0x12b0
>  ? __tcp_select_window+0x380/0x380
>  tcp_write_xmit+0x913/0x1de0
>  ? __sk_mem_schedule+0x50/0x80
>  tcp_sendmsg_locked+0x49d/0x15a0
>  ? tcp_rcv_established+0x8da/0xa30
>  ? tcp_set_state+0x220/0x220
>  ? clear_user+0x1f/0x50
>  ? iov_iter_zero+0x1ae/0x590
>  ? __fget_light+0xa0/0xe0
>  tcp_sendmsg+0x22/0x40
>  __sys_sendto+0x1b0/0x250
>  ? __ia32_sys_getpeername+0x40/0x40
>  ? _copy_to_user+0x58/0x70
>  ? poll_select_copy_remaining+0x176/0x200
>  ? __pollwait+0x1c0/0x1c0
>  ? ktime_get_ts64+0x11f/0x140
>  ? kern_select+0x108/0x150
>  ? core_sys_select+0x360/0x360
>  ? vfs_read+0x127/0x150
>  ? kernel_write+0x90/0x90
>  __x64_sys_sendto+0x6f/0x80
>  do_syscall_64+0x5d/0x150
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x7fefef2b129d
> Code: ff ff ff ff eb b6 0f 1f 80 00 00 00 00 48 8d 05 51 37 0c 00 41 89 ca 8b 00 85 c0 75 20 45 31 c9 45 31 c0 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 6b f3 c3 66 0f 1f 84 00 00 00 00 00 41 56 41
> RSP: 002b:00007fff2f5350c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 000056118d60c120 RCX: 00007fefef2b129d
> RDX: 0000000000002000 RSI: 000056118d629320 RDI: 0000000000000003
> RBP: 000056118d530370 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000002000
> R13: 000056118d5c2a10 R14: 000056118d5c2a10 R15: 000056118d5303b8
>
>tcf_sample_act() tried to update its per-cpu stats, but tcf_sample_init()
>forgot to allocate them, because tcf_idr_create() was called with a wrong
>value of 'cpustats'. Setting it to true proved to fix the reported crash.
>
>Reported-by: Matteo Croce <mcroce@...hat.com>
>Fixes: 65a206c01e8e ("net/sched: Change act_api and act_xxx modules to use IDR")
>Fixes: 5c5670fae430 ("net/sched: Introduce sample tc action")
>Tested-by: Matteo Croce <mcroce@...hat.com>
>Signed-off-by: Davide Caratti <dcaratti@...hat.com>

Acked-by: Jiri Pirko <jiri@...lanox.com>