* Re: Kernel hangs on regulatory.db X.509 key initialization
2019-02-17 12:29 ` Maciej S. Szmigiero
@ 2019-02-17 15:47 ` Dominik Schmidt
0 siblings, 0 replies; 3+ messages in thread
From: Dominik Schmidt @ 2019-02-17 15:47 UTC (permalink / raw)
To: Maciej S. Szmigiero; +Cc: james.morris, linux-wireless
Excerpts from Maciej S. Szmigiero's message of Februar 17, 2019 1:29 pm:
> Hi,
>
> On 17.02.2019 10:38, Dominik Schmidt wrote:
>> Hi there!
>>
>> I'm running a Gentoo Linux on an APU2C2-Board (AMD Jaguar GX-412TC x86_64), with
>> an Atheros QCA9882 (ath10k) and an Atheros AR9280 (ath9k) card.
>>
>> The kernels after 4.18 do not reach userspace any longer.
>
> Did you test a more recent kernel like 4.20?
Yes, up to 4.20.7, yielding the same fault
>> They just somehow
>> "freeze" without emitting any oops or kernel panic. I've tracked the issue
>> down to the cfg80211 subsystem and a change in the X.509 parser:
>>
>> * If I do not compile cfg80211 into the kernel, it starts perfectly (minus wireless)
>>
>> * Bisecting the issue shows that it starts with
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b65c32ec5a942ab3ada93a048089a938918aba7f
>>
>> * The last message I see in the logs is this one:
>> cfg80211: Loading compiled-in X.509 certificates for regulatory database
>> defined at
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/net/wireless/reg.c#n770
>>
>> * If I add another pr_notice to the end of that function, it is never displayed.
>>
>> * It seems to get stuck at the call to key_create_or_update, here:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/net/wireless/reg.c#n735
>>
>> * If I throw more pr_notices at key_create_or_update, the last one I see
>> is before this memset:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/security/keys/key.c#n843
>>
>> * As an additional hindrance, this problem occurs only on the APU2 board,
>> and not when running the same kernel in a Qemu-VM
>>
>> Any idea what could be the cause of this, or hints as to how to
>> debug this further?
>
> I see that you are using an AMD CPU-based board, with AMD CCP enabled
> in your kernel config.
>
> Before my patch, that you bisected your problem to, such configuration
> would fail (early) in-kernel X.509 certificate signature verification
> as its length wasn't exactly correct.
Yes, it did/does actually fail with:
[ 7.376473] cfg80211: Loading compiled-in X.509 certificates for regulatory database
[ 7.388090] cfg80211: Problem loading in-kernel X.509 certificate (-22)
[ 7.406107] cfg80211: failed to load regulatory.db
> Now, when this was fixed the CCP RSA implementation actually gets
> exercised (however, it works for me without problems on Ryzen).
In deed it seems that CCP might be the culprit here, nice catch.
If I remove the option, the kernel starts up nicely with:
[ 7.097244] cfg80211: Loading compiled-in X.509 certificates for regulatory database
[ 7.109893] cfg80211: Loaded X.509 cert 'sforshee: 00b28ddf47aef9cea7'
[ 7.117763] platform regulatory.0: Direct firmware load for regulatory.db failed with error -2
[ 7.129880] cfg80211: failed to load regulatory.db
> You can temporarily change CONFIG_CFG80211 in your kernel config to
> 'm' and compile the kernel with KASAN.
> Don't load any wireless modules at startup, this should at least
> defer the crash until you load them manually later when the system is
> idle and you can monitor it.
>
> If you are lucky KASAN will give you information then where the bug
> might be.
Oh, this works marvellously:
[ 23.301826] ==================================================================
[ 23.309463] BUG: KASAN: slab-out-of-bounds in ccp_rsa_crypt+0x84/0x250
[ 23.316092] Write of size 296 at addr ffff88805ba00c40 by task swapper/0/1
[ 23.323030]
[ 23.324633] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G T 4.20.7 #38
[ 23.332121] Hardware name: PC Engines apu2/apu2, BIOS v4.9.0.1 01/09/2019
[ 23.339051] Call Trace:
[ 23.341610] dump_stack+0xd1/0x160
[ 23.345123] ? dump_stack_print_info.cold.0+0x1b/0x1b
[ 23.350321] ? kmsg_dump_rewind_nolock+0x60/0x60
[ 23.355093] print_address_description.cold.3+0x9/0x26a
[ 23.360465] kasan_report.cold.4+0x65/0xa3
[ 23.364662] ? ccp_rsa_crypt+0x84/0x250
[ 23.368605] memset+0x2d/0x50
[ 23.371681] ccp_rsa_crypt+0x84/0x250
[ 23.375506] ? ccp_rsa_exit_tfm+0x10/0x10
[ 23.379651] pkcs1pad_verify+0x254/0x2c0
[ 23.383706] public_key_verify_signature+0x385/0x5b0
[ 23.388800] ? software_key_query+0x2f0/0x2f0
[ 23.393285] ? ret_from_fork+0x27/0x50
[ 23.397157] ? sha256_base_init+0xa0/0xa0
[ 23.401319] ? match_held_lock+0xb8/0x380
[ 23.405485] ? __lock_acquire+0x2d30/0x2d30
[ 23.409807] ? x509_get_sig_params+0x223/0x280
[ 23.414385] ? kasan_unpoison_shadow+0x3b/0x60
[ 23.418931] ? kasan_kmalloc+0xee/0x100
[ 23.422929] ? asymmetric_key_generate_id+0x3e/0xa0
[ 23.427925] x509_check_for_self_signed+0x183/0x20c
[ 23.432919] ? asymmetric_key_generate_id+0x77/0xa0
[ 23.437930] x509_cert_parse+0x315/0x3c0
[ 23.441958] x509_key_preparse+0x47/0x3a0
[ 23.446084] asymmetric_key_preparse+0x60/0x90
[ 23.450648] key_create_or_update+0x3aa/0x8b0
[ 23.455107] ? key_type_lookup+0x90/0x90
[ 23.459195] ? key_instantiate_and_link+0x250/0x2c0
[ 23.464144] ? key_user_put+0x50/0x50
[ 23.467943] regulatory_init_db+0x20d/0x386
[ 23.472245] ? regulatory_init+0x201/0x201
[ 23.476471] do_one_initcall+0xd5/0x458
[ 23.480436] ? perf_trace_initcall_level+0x370/0x370
[ 23.485499] ? strlen+0x5/0x40
[ 23.488697] ? next_arg+0x19c/0x220
[ 23.492291] ? strlen+0x1e/0x40
[ 23.495508] ? rcu_is_watching+0xa5/0xf0
[ 23.499532] ? __lock_is_held+0x38/0xd0
[ 23.503472] ? rcu_gpnum_ovf+0x210/0x210
[ 23.507499] ? rcu_read_lock_sched_held+0x70/0x80
[ 23.512328] ? trace_initcall_level+0x15b/0x1bc
[ 23.516964] ? do_one_initcall+0x400/0x458
[ 23.521192] ? up_write+0xcf/0x180
[ 23.524674] ? down_read_non_owner+0xb0/0xb0
[ 23.529105] ? kasan_unpoison_shadow+0x3b/0x60
[ 23.533654] kernel_init_freeable+0x511/0x60e
[ 23.538103] ? rest_init+0x2df/0x2df
[ 23.541782] kernel_init+0x7/0x121
[ 23.545263] ? rest_init+0x2df/0x2df
[ 23.548912] ret_from_fork+0x27/0x50
[ 23.552583]
[ 23.554173] Allocated by task 1:
[ 23.557564] kasan_kmalloc+0xee/0x100
[ 23.561325] __kmalloc+0x123/0x280
[ 23.564859] public_key_verify_signature+0x157/0x5b0
[ 23.569893] x509_check_for_self_signed+0x183/0x20c
[ 23.574899] x509_cert_parse+0x315/0x3c0
[ 23.578913] x509_key_preparse+0x47/0x3a0
[ 23.582993] asymmetric_key_preparse+0x60/0x90
[ 23.587565] key_create_or_update+0x3aa/0x8b0
[ 23.592047] regulatory_init_db+0x20d/0x386
[ 23.596332] do_one_initcall+0xd5/0x458
[ 23.600273] kernel_init_freeable+0x511/0x60e
[ 23.604714] kernel_init+0x7/0x121
[ 23.608228] ret_from_fork+0x27/0x50
[ 23.611928]
[ 23.613522] Freed by task 0:
[ 23.616497] (stack is not available)
[ 23.620158]
[ 23.621740] The buggy address belongs to the object at ffff88805ba00b40
[ 23.621740] which belongs to the cache kmalloc-256 of size 256
[ 23.634410] The buggy address is located 0 bytes to the right of
[ 23.634410] 256-byte region [ffff88805ba00b40, ffff88805ba00c40)
[ 23.646599] The buggy address belongs to the page:
[ 23.651537] page:ffffea00016e8000 count:1 mapcount:0 mapping:ffff88805f803200 index:0x0 compound_mapcount: 0
[ 23.661500] flags: 0x4000000000010200(slab|head)
[ 23.666272] raw: 4000000000010200 dead000000000100 dead000000000200 ffff88805f803200
[ 23.674178] raw: 0000000000000000 0000000080190019 00000001ffffffff 0000000000000000
[ 23.682028] page dumped because: kasan: bad access detected
[ 23.687724]
[ 23.689329] Memory state around the buggy address:
[ 23.694255] ffff88805ba00b00: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
[ 23.701593] ffff88805ba00b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 23.708926] >ffff88805ba00c00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
[ 23.716304] ^
[ 23.721725] ffff88805ba00c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 23.729058] ffff88805ba00d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 23.736370] ==================================================================
[ 23.743664] Disabling lock debugging due to kernel taint
I will investigate further and start a new thread in linux-crypto once I find out more
(sorry about abusing linux-wireless :/)
Anyways, many thanks Maciej for looking into it, your help is much appreciated!
>> Cheers
>> Dominik
>>
>
> Maciej
>
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