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Date:   Sun, 24 Apr 2022 20:11:30 +0800
From:   Solomon Tan <wjsota@gmail.com>
To:     Michael Straube <straube.linux@gmail.com>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        Larry Finger <Larry.Finger@lwfinger.net>,
        Phillip Potter <phil@philpotter.co.uk>,
        "open list:STAGING SUBSYSTEM" <linux-staging@lists.linux.dev>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [BUG] staging: r8188eu: KASAN: slab-out-of-bounds in
 rtw_cmd_thread
Message-ID: <YmU+cqEZfrGz5XsT@ArchDesktop>
References: <67e2d10b-7f0f-9c5a-ce31-376b83ffba9e@gmail.com>
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On Sun, Apr 24, 2022 at 12:00:12PM +0200, Michael Straube wrote:
> Hi,
> 
> It looks like
> commit 0afaa121813e ("staging: r8188eu: use in-kernel ieee channel")
> intoduced a. See KASAN output below.
> 
> That commit replaced the use of struct rtw_ieee80211_channel with struct
> ieee80211_channel.
> 
> There are several calls to memcpy that used sizeof(struct
> rtw_ieee80211_channel)
> and now use sizeof(struct ieee80211_channel) but the sizes of these two
> structures are not equal.
> 

Oh no. When does this issue get triggered?

> regards,
> Michael
> 
> dmesg:
> 
>  ==================================================================
> [  422.214237] BUG: KASAN: slab-out-of-bounds in rtw_cmd_thread+0x1e8/0x430
> [r8188eu]
> [  422.214277] Write of size 3600 at addr ffff8881e149d200 by task
> RTW_CMD_THREAD/2563
> 
> [  422.214289] CPU: 11 PID: 2563 Comm: RTW_CMD_THREAD Tainted: G C OE
> 5.18.0-rc2-staging+ #47 94e3ca73bebf5b7fec506721475e4fff2a023bb9
> [  422.214301] Hardware name: Gigabyte Technology Co., Ltd. B550M S2H/B550M
> S2H, BIOS F15a 02/16/2022
> [  422.214309] Call Trace:
> [  422.214313]  <TASK>
> [  422.214317]  dump_stack_lvl+0x45/0x5b
> [  422.214327]  print_report.cold+0x5e/0x5dc
> [  422.214335]  ? kasan_set_track+0x21/0x30
> [  422.214342]  ? kasan_set_free_info+0x20/0x40
> [  422.214349]  ? rtw_cmd_thread+0x1e8/0x430 [r8188eu
> 91924fe1575bf49b9b37985ffde2c585d847446d]
> [  422.214386]  kasan_report+0xab/0x120
> [  422.214394]  ? rtw_cmd_thread+0x1e8/0x430 [r8188eu
> 91924fe1575bf49b9b37985ffde2c585d847446d]
> [  422.214430]  kasan_check_range+0xf6/0x1d0
> [  422.214436]  memcpy+0x39/0x60
> [  422.214442]  rtw_cmd_thread+0x1e8/0x430 [r8188eu
> 91924fe1575bf49b9b37985ffde2c585d847446d]
> [  422.214479]  ? rtw_setassocsta_cmdrsp_callback+0xd0/0xd0 [r8188eu
> 91924fe1575bf49b9b37985ffde2c585d847446d]
> [  422.214516]  kthread+0x15d/0x190
> [  422.214523]  ? kthread_complete_and_exit+0x20/0x20
> [  422.214531]  ret_from_fork+0x22/0x30
> [  422.214540]  </TASK>

Sorry, I am not familiar with KASAN. How should I interpret this output?
I see the paragraph above has references to rtw_cmd_thread. I assume
that is its way of indicating that rtw_cmd_thread is the cause of the
problem, but the one below refers to other functions. I'm not sure where
I should start looking. I would start looking at `rtw_sitesurvey_cmd` and
`rtw_scan_ch_decision`, which call the memcpy on the
rtw_ieee80211_channel structure, but they are not on the call trace.

> 
> [  422.214546] Allocated by task 2522:
> [  422.214551]  kasan_save_stack+0x1e/0x40
> [  422.214555]  __kasan_kmalloc+0xa9/0xe0
> [  422.214559]  rtw_init_cmd_priv+0xd6/0x1b0 [r8188eu]
> [  422.214589]  rtw_init_drv_sw+0x21/0x370 [r8188eu]
> [  422.214619]  rtw_drv_init+0x3a6/0x4f0 [r8188eu]
> [  422.214649]  usb_probe_interface+0x155/0x340 [usbcore]
> [  422.214705]  really_probe.part.0+0x11f/0x320
> [  422.214709]  __driver_probe_device+0xe0/0x180
> [  422.214712]  driver_probe_device+0x4d/0x170
> [  422.214715]  __driver_attach+0x110/0x250
> [  422.214718]  bus_for_each_dev+0xe7/0x140
> [  422.214721]  bus_add_driver+0x25a/0x2b0
> [  422.214723]  driver_register+0x10f/0x190
> [  422.214726]  usb_register_driver+0x10e/0x1e0 [usbcore]
> [  422.214780]  do_one_initcall+0x8a/0x2a0
> [  422.214784]  do_init_module+0xe4/0x3b0
> [  422.214787]  load_module+0x41c4/0x4650
> [  422.214789]  __do_sys_finit_module+0x111/0x190
> [  422.214791]  do_syscall_64+0x5c/0x80
> [  422.214795]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> [  422.214802] Last potentially related work creation:
> [  422.214807]  kasan_save_stack+0x1e/0x40
> [  422.214810]  __kasan_record_aux_stack+0xb1/0xc0
> [  422.214813]  call_rcu+0xb5/0xfc0
> [  422.214817]  netlink_release+0x791/0xa40
> [  422.214820]  __sock_release+0x72/0x120
> [  422.214824]  sock_close+0x11/0x20
> [  422.214828]  __fput+0x10c/0x400
> [  422.214831]  task_work_run+0x8b/0xc0
> [  422.214834]  do_exit+0x5a4/0x10e0
> [  422.214837]  do_group_exit+0x58/0x100
> [  422.214840]  __x64_sys_exit_group+0x28/0x30
> [  422.214843]  do_syscall_64+0x5c/0x80
> [  422.214846]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> [  422.214852] The buggy address belongs to the object at ffff8881e149d000
>                 which belongs to the cache kmalloc-2k of size 2048
> [  422.214862] The buggy address is located 512 bytes inside of
>                 2048-byte region [ffff8881e149d000, ffff8881e149d800)
> 
> [  422.214874] The buggy address belongs to the physical page:
> [  422.214879] page:000000003f187866 refcount:1 mapcount:0
> mapping:0000000000000000 index:0x0 pfn:0x1e1498
> [  422.214883] head:000000003f187866 order:3 compound_mapcount:0
> compound_pincount:0
> [  422.214885] flags:
> 0x17ffffc0010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff)
> [  422.214891] raw: 0017ffffc0010200 ffffea0004f1ca00 dead000000000002
> ffff888100042f00
> [  422.214894] raw: 0000000000000000 0000000000080008 00000001ffffffff
> 0000000000000000
> [  422.214896] page dumped because: kasan: bad access detected
> 
> [  422.214900] Memory state around the buggy address:
> [  422.214905]  ffff8881e149d500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 00 00
> [  422.214914]  ffff8881e149d580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 00 00
> [  422.214921] >ffff8881e149d600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> fc fc
> [  422.214927]                    ^
> [  422.214932]  ffff8881e149d680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> fc fc
> [  422.214939]  ffff8881e149d700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> fc fc
> [  422.214946]
> ==================================================================