Hi Stephen,
In drbg driver local variable of function are added as list nodes. one
instance is given below.
static inline int __init drbg_healthcheck_sanity(void)
---
---
max_addtllen = drbg_max_addtl(drbg);
max_request_bytes = drbg_max_request_bytes(drbg);
drbg_string_fill(&addtl, buf, max_addtllen + 1);
/* overflow addtllen with additonal info string */
len = drbg_generate(drbg, buf, OUTBUFLEN, &addtl);
===> Added "addtllist" to the tail. which local variable.
BUG_ON(0 < len);
/* overflow max_bits */
len = drbg_generate(drbg, buf, (max_request_bytes + 1), NULL);
BUG_ON(0 < len);
/* overflow max addtllen with personalization string */
ret = drbg_seed(drbg, &addtl, false);
====> Added "seedlist" to the tail of same list. Previous
node(addtllist) already invalid(Out of scope when function returns)
BUG_ON(0 == ret);
/* all tests passed */
rc = 0;
Is't a BUG? or I missed something.
Regards
Harsh Jain
Am Mittwoch, 3. Mai 2017, 14:47:24 CEST schrieb Harsh Jain:
Hi Harsh,
> Hi Stephen,
>
> In drbg driver local variable of function are added as list nodes. one
> instance is given below.
>
>
> static inline int __init drbg_healthcheck_sanity(void)
>
>
>
> ---
> ---
>
> max_addtllen = drbg_max_addtl(drbg);
> max_request_bytes = drbg_max_request_bytes(drbg);
> drbg_string_fill(&addtl, buf, max_addtllen + 1);
> /* overflow addtllen with additonal info string */
> len = drbg_generate(drbg, buf, OUTBUFLEN, &addtl);
>
> ===> Added "addtllist" to the tail. which local variable.
>
>
> BUG_ON(0 < len);
> /* overflow max_bits */
> len = drbg_generate(drbg, buf, (max_request_bytes + 1), NULL);
> BUG_ON(0 < len);
>
> /* overflow max addtllen with personalization string */
> ret = drbg_seed(drbg, &addtl, false);
>
> ====> Added "seedlist" to the tail of same list. Previous
> node(addtllist) already invalid(Out of scope when function returns)
>
>
> BUG_ON(0 == ret);
> /* all tests passed */
> rc = 0;
>
>
>
> Is't a BUG? or I missed something.
:-) You are right that in normal processing this is a bug. But this is a
special function which shall perform a sanity checks for the maximum length
enforcement. Thus, addtllist or seedlist should never be filled.
To be precise: The called code is expected to return an error before the
variables are used due to the length checks. If these errors do not appear,
something is wrong with the DRBG which causes the BUG_ON.
The following error conditions are triggered:
/* 9.3.1 step 2 */
len = -EINVAL;
if (buflen > (drbg_max_request_bytes(drbg))) {
pr_devel("DRBG: requested random numbers too large %u\n",
buflen);
goto err;
}
/* 9.3.1 step 4 */
if (addtl && addtl->len > (drbg_max_addtl(drbg))) {
pr_devel("DRBG: additional information string too long %zu\n",
addtl->len);
goto err;
}
Ciao
Stephan
On Wed, May 3, 2017 at 6:41 PM, Stephan Müller <[email protected]> wrote:
> Am Mittwoch, 3. Mai 2017, 14:47:24 CEST schrieb Harsh Jain:
>
> Hi Harsh,
>
>> Hi Stephen,
>>
>> In drbg driver local variable of function are added as list nodes. one
>> instance is given below.
>>
>>
>> static inline int __init drbg_healthcheck_sanity(void)
>>
>>
>>
>> ---
>> ---
>>
>> max_addtllen = drbg_max_addtl(drbg);
>> max_request_bytes = drbg_max_request_bytes(drbg);
>> drbg_string_fill(&addtl, buf, max_addtllen + 1);
>> /* overflow addtllen with additonal info string */
>> len = drbg_generate(drbg, buf, OUTBUFLEN, &addtl);
>>
>> ===> Added "addtllist" to the tail. which local variable.
>>
>>
>> BUG_ON(0 < len);
>> /* overflow max_bits */
>> len = drbg_generate(drbg, buf, (max_request_bytes + 1), NULL);
>> BUG_ON(0 < len);
>>
>> /* overflow max addtllen with personalization string */
>> ret = drbg_seed(drbg, &addtl, false);
>>
>> ====> Added "seedlist" to the tail of same list. Previous
>> node(addtllist) already invalid(Out of scope when function returns)
>>
>>
>> BUG_ON(0 == ret);
>> /* all tests passed */
>> rc = 0;
>>
>>
>>
>> Is't a BUG? or I missed something.
>
> :-) You are right that in normal processing this is a bug. But this is a
> special function which shall perform a sanity checks for the maximum length
> enforcement. Thus, addtllist or seedlist should never be filled.
>
> To be precise: The called code is expected to return an error before the
> variables are used due to the length checks. If these errors do not appear,
> something is wrong with the DRBG which causes the BUG_ON.
Confusing, I have to dig more for DRBG. Actually we observed following
panic in Chcr (Chelsio) when drgb is enabled and Panic trace points
some thing wrong
with drgb modules. Any idea what are possible reason for this.
alg: No test for authenc(digest_null,rfc3686(ctr(aes)))
(authenc(digest_null-generic,rfc3686-ctr-aes-chcr))
alg: No test for seqiv(authenc(digest_null,rfc3686(ctr(aes))))
(seqiv(authenc(digest_null-generic,rfc3686-ctr-aes-chcr)))
alg: No test for fips(ansi_cprng) (fips_ansi_cprng)
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff81317c66>] __list_add+0x26/0xd0
PGD 0
Oops: 0000 [#1] SMP
Modules linked in: drbg(+) ansi_cprng seqiv xfrm6_mode_tunnel
xfrm4_mode_tunnel xfrm4_tunnel tunnel4 ipcomp xfrm_ipcomp esp4 ah4
af_key cbc ccm ctr ghash_generic gf128mul ghash_clmulni_intel cryptd
gcm sha512_ssse3 sha512_generic chcr(OE) cxgb4(OE) authenc netconsole
configfs xt_nat iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4
nf_nat_ipv4 nf_nat nf_conntrack ip_tables nfsd lockd grace nfs_acl
auth_rpcgss sunrpc ipv6 crc_ccitt vfat fat joydev iTCO_wdt
iTCO_vendor_support mxm_wmi pcspkr sg i2c_i801 i2c_smbus lpc_ich
mfd_core shpchp xhci_pci xhci_hcd igb i2c_algo_bit i2c_core ptp
pps_core ioatdma dca ipmi_si ipmi_msghandler wmi acpi_cpufreq acpi_pad
dm_mod(E) ext4(E) mbcache(E) jbd2(E) sd_mod(E) ahci(E) libahci(E)
[last unloaded: scsi_transport_fc]
CPU: 9 PID: 3672 Comm: cryptomgr_test Tainted: G OE 4.9.13 #2
Hardware name: Supermicro X10DRi/X10DRi, BIOS 2.0 12/28/2015
task: ffff88103b418a00 task.stack: ffffc90008a7c000
RIP: 0010:[<ffffffff81317c66>] [<ffffffff81317c66>] __list_add+0x26/0xd0
RSP: 0018:ffffc90008a7f8c8 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffffc90008a7f920 RCX: 0000000000000001
RDX: ffff88103c8b5ef0 RSI: 0000000000000000 RDI: ffffc90008a7f920
RBP: ffffc90008a7f8f8 R08: 0000000000000000 R09: ffff8810053200b0
R10: ffff88103caf3100 R11: 0000000000000020 R12: ffff88103c8b5ef0
R13: 0000000000000000 R14: ffff88103b418a00 R15: 7fffffffffffffff
FS: 0000000000000000(0000) GS:ffff88107f440000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000001c07000 CR4: 00000000001406e0
Stack:
ffffc90008a7f8e8 0000000000000246 ffff88103caf3040 ffff88103c8b5ee0
ffff88103c8b5ee8 ffffc90008a7f908 ffffc90008a7f968 ffffffff81654c02
0000000000000001 ffff88103b418a00 ffffffff81097370 0000000000000000
Call Trace:
[<ffffffff81654c02>] wait_for_completion_interruptible+0xc2/0x130
[<ffffffff81097370>] ? try_to_wake_up+0x240/0x240
[<ffffffffa02582fb>] drbg_kcapi_sym_ctr+0xeb/0x150 [drbg]
[<ffffffffa0259560>] drbg_ctr_update+0x1b0/0x2a0 [drbg]
[<ffffffffa0259bd2>] drbg_seed+0x1a2/0x2e0 [drbg]
[<ffffffffa025a6ef>] ? drbg_init_sym_kernel+0x13f/0x200 [drbg]
[<ffffffffa025aa62>] drbg_instantiate+0x52/0x1e0 [drbg]
[<ffffffff811ca2ee>] ? __kmalloc+0xee/0x1d0
[<ffffffff812a873d>] ? crypto_create_tfm+0x3d/0xd0
[<ffffffffa025acbc>] drbg_kcapi_seed+0xcc/0x118 [drbg]
[<ffffffff812a87a1>] ? crypto_create_tfm+0xa1/0xd0
[<ffffffff812bb48d>] crypto_rng_reset+0x5d/0x80
[<ffffffff812b5197>] drbg_cavs_test+0xf7/0x370
[<ffffffff810a3018>] ? dequeue_task_fair+0x68/0x420
[<ffffffff8109ccd5>] ? pick_next_task_idle+0x45/0x50
[<ffffffff812b547b>] alg_test_drbg+0x6b/0xa0
[<ffffffff812b18d5>] alg_test+0x145/0x350
[<ffffffff812b0ad0>] ? cryptomgr_probe+0xd0/0xd0
[<ffffffff812b0ad0>] ? cryptomgr_probe+0xd0/0xd0
[<ffffffff812b0b15>] cryptomgr_test+0x45/0x50
[<ffffffff8108a5ed>] kthread+0xcd/0xf0
[<ffffffff8109503e>] ? schedule_tail+0x1e/0xc0
[<ffffffff8108a520>] ? __kthread_init_worker+0x40/0x40
[<ffffffff81657bd2>] ret_from_fork+0x22/0x30
Code: 00 00 00 00 00 55 48 89 e5 48 83 ec 30 48 89 5d e8 4c 89 65 f0
48 89 fb 4c 89 6d f8 4c 8b 42 08 49 89 f5 49 89 d4 49 39 f0 75 31 <4d>
8b 45 00 4d 39 c4 75 6f 4c 39 e3 74 45 4c 39 eb 74 40 49 89
RIP [<ffffffff81317c66>] __list_add+0x26/0xd0
RSP <ffffc90008a7f8c8>
CR2: 0000000000000000
---[ end trace fbf11c880e8c4c52 ]---
>
> The following error conditions are triggered:
>
> /* 9.3.1 step 2 */
> len = -EINVAL;
> if (buflen > (drbg_max_request_bytes(drbg))) {
> pr_devel("DRBG: requested random numbers too large %u\n",
> buflen);
> goto err;
> }
>
> /* 9.3.1 step 4 */
> if (addtl && addtl->len > (drbg_max_addtl(drbg))) {
> pr_devel("DRBG: additional information string too long %zu\n",
> addtl->len);
> goto err;
> }
>
>
> Ciao
> Stephan
Am Montag, 8. Mai 2017, 08:30:13 CEST schrieb Harsh Jain:
Hi Harsh,
>
> Confusing, I have to dig more for DRBG. Actually we observed following
> panic in Chcr (Chelsio) when drgb is enabled and Panic trace points
> some thing wrong
> with drgb modules. Any idea what are possible reason for this.
Just to confirm: are you using the latest kernel? The bug you are referring to
happens in the drbg_kcapi_sym_ctr called by the update operation to process
seed material. This function had a bug in it where I used stack buffer. This
is now repaced with heap buffer:
5102981212454998d549273ff9847f19e97a1794
I am yet wondering why a __list_add is called that causes the bug. In the DRBG
code path seen below, I am not seeing any list_add calls.
>
> alg: No test for authenc(digest_null,rfc3686(ctr(aes)))
> (authenc(digest_null-generic,rfc3686-ctr-aes-chcr))
> alg: No test for seqiv(authenc(digest_null,rfc3686(ctr(aes))))
> (seqiv(authenc(digest_null-generic,rfc3686-ctr-aes-chcr)))
> alg: No test for fips(ansi_cprng) (fips_ansi_cprng)
> BUG: unable to handle kernel NULL pointer dereference at (null)
> IP: [<ffffffff81317c66>] __list_add+0x26/0xd0
> PGD 0
> Oops: 0000 [#1] SMP
> Modules linked in: drbg(+) ansi_cprng seqiv xfrm6_mode_tunnel
> xfrm4_mode_tunnel xfrm4_tunnel tunnel4 ipcomp xfrm_ipcomp esp4 ah4
> af_key cbc ccm ctr ghash_generic gf128mul ghash_clmulni_intel cryptd
> gcm sha512_ssse3 sha512_generic chcr(OE) cxgb4(OE) authenc netconsole
> configfs xt_nat iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4
> nf_nat_ipv4 nf_nat nf_conntrack ip_tables nfsd lockd grace nfs_acl
> auth_rpcgss sunrpc ipv6 crc_ccitt vfat fat joydev iTCO_wdt
> iTCO_vendor_support mxm_wmi pcspkr sg i2c_i801 i2c_smbus lpc_ich
> mfd_core shpchp xhci_pci xhci_hcd igb i2c_algo_bit i2c_core ptp
> pps_core ioatdma dca ipmi_si ipmi_msghandler wmi acpi_cpufreq acpi_pad
> dm_mod(E) ext4(E) mbcache(E) jbd2(E) sd_mod(E) ahci(E) libahci(E)
> [last unloaded: scsi_transport_fc]
> CPU: 9 PID: 3672 Comm: cryptomgr_test Tainted: G OE 4.9.13 #2
> Hardware name: Supermicro X10DRi/X10DRi, BIOS 2.0 12/28/2015
> task: ffff88103b418a00 task.stack: ffffc90008a7c000
> RIP: 0010:[<ffffffff81317c66>] [<ffffffff81317c66>] __list_add+0x26/0xd0
> RSP: 0018:ffffc90008a7f8c8 EFLAGS: 00010046
> RAX: 0000000000000000 RBX: ffffc90008a7f920 RCX: 0000000000000001
> RDX: ffff88103c8b5ef0 RSI: 0000000000000000 RDI: ffffc90008a7f920
> RBP: ffffc90008a7f8f8 R08: 0000000000000000 R09: ffff8810053200b0
> R10: ffff88103caf3100 R11: 0000000000000020 R12: ffff88103c8b5ef0
> R13: 0000000000000000 R14: ffff88103b418a00 R15: 7fffffffffffffff
> FS: 0000000000000000(0000) GS:ffff88107f440000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000000 CR3: 0000000001c07000 CR4: 00000000001406e0
> Stack:
> ffffc90008a7f8e8 0000000000000246 ffff88103caf3040 ffff88103c8b5ee0
> ffff88103c8b5ee8 ffffc90008a7f908 ffffc90008a7f968 ffffffff81654c02
> 0000000000000001 ffff88103b418a00 ffffffff81097370 0000000000000000
> Call Trace:
> [<ffffffff81654c02>] wait_for_completion_interruptible+0xc2/0x130
> [<ffffffff81097370>] ? try_to_wake_up+0x240/0x240
> [<ffffffffa02582fb>] drbg_kcapi_sym_ctr+0xeb/0x150 [drbg]
> [<ffffffffa0259560>] drbg_ctr_update+0x1b0/0x2a0 [drbg]
> [<ffffffffa0259bd2>] drbg_seed+0x1a2/0x2e0 [drbg]
> [<ffffffffa025a6ef>] ? drbg_init_sym_kernel+0x13f/0x200 [drbg]
> [<ffffffffa025aa62>] drbg_instantiate+0x52/0x1e0 [drbg]
> [<ffffffff811ca2ee>] ? __kmalloc+0xee/0x1d0
> [<ffffffff812a873d>] ? crypto_create_tfm+0x3d/0xd0
> [<ffffffffa025acbc>] drbg_kcapi_seed+0xcc/0x118 [drbg]
> [<ffffffff812a87a1>] ? crypto_create_tfm+0xa1/0xd0
> [<ffffffff812bb48d>] crypto_rng_reset+0x5d/0x80
> [<ffffffff812b5197>] drbg_cavs_test+0xf7/0x370
> [<ffffffff810a3018>] ? dequeue_task_fair+0x68/0x420
> [<ffffffff8109ccd5>] ? pick_next_task_idle+0x45/0x50
> [<ffffffff812b547b>] alg_test_drbg+0x6b/0xa0
> [<ffffffff812b18d5>] alg_test+0x145/0x350
> [<ffffffff812b0ad0>] ? cryptomgr_probe+0xd0/0xd0
> [<ffffffff812b0ad0>] ? cryptomgr_probe+0xd0/0xd0
> [<ffffffff812b0b15>] cryptomgr_test+0x45/0x50
> [<ffffffff8108a5ed>] kthread+0xcd/0xf0
> [<ffffffff8109503e>] ? schedule_tail+0x1e/0xc0
> [<ffffffff8108a520>] ? __kthread_init_worker+0x40/0x40
> [<ffffffff81657bd2>] ret_from_fork+0x22/0x30
> Code: 00 00 00 00 00 55 48 89 e5 48 83 ec 30 48 89 5d e8 4c 89 65 f0
> 48 89 fb 4c 89 6d f8 4c 8b 42 08 49 89 f5 49 89 d4 49 39 f0 75 31 <4d>
> 8b 45 00 4d 39 c4 75 6f 4c 39 e3 74 45 4c 39 eb 74 40 49 89
> RIP [<ffffffff81317c66>] __list_add+0x26/0xd0
> RSP <ffffc90008a7f8c8>
> CR2: 0000000000000000
> ---[ end trace fbf11c880e8c4c52 ]---
Ciao
Stephan
On Mon, May 8, 2017 at 2:00 PM, Stephan Müller <[email protected]> wrote:
> Am Montag, 8. Mai 2017, 08:30:13 CEST schrieb Harsh Jain:
>
> Hi Harsh,
>>
>> Confusing, I have to dig more for DRBG. Actually we observed following
>> panic in Chcr (Chelsio) when drgb is enabled and Panic trace points
>> some thing wrong
>> with drgb modules. Any idea what are possible reason for this.
>
> Just to confirm: are you using the latest kernel?
No, I tried on 4.9.13. Will let you know the behavior with latest kernel.
The bug you are referring to
> happens in the drbg_kcapi_sym_ctr called by the update operation to process
> seed material. This function had a bug in it where I used stack buffer. This
> is now repaced with heap buffer:
>
> 5102981212454998d549273ff9847f19e97a1794
>
> I am yet wondering why a __list_add is called that causes the bug. In the DRBG
> code path seen below, I am not seeing any list_add calls.
>>
>> alg: No test for authenc(digest_null,rfc3686(ctr(aes)))
>> (authenc(digest_null-generic,rfc3686-ctr-aes-chcr))
>> alg: No test for seqiv(authenc(digest_null,rfc3686(ctr(aes))))
>> (seqiv(authenc(digest_null-generic,rfc3686-ctr-aes-chcr)))
>> alg: No test for fips(ansi_cprng) (fips_ansi_cprng)
>> BUG: unable to handle kernel NULL pointer dereference at (null)
>> IP: [<ffffffff81317c66>] __list_add+0x26/0xd0
>> PGD 0
>> Oops: 0000 [#1] SMP
>> Modules linked in: drbg(+) ansi_cprng seqiv xfrm6_mode_tunnel
>> xfrm4_mode_tunnel xfrm4_tunnel tunnel4 ipcomp xfrm_ipcomp esp4 ah4
>> af_key cbc ccm ctr ghash_generic gf128mul ghash_clmulni_intel cryptd
>> gcm sha512_ssse3 sha512_generic chcr(OE) cxgb4(OE) authenc netconsole
>> configfs xt_nat iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4
>> nf_nat_ipv4 nf_nat nf_conntrack ip_tables nfsd lockd grace nfs_acl
>> auth_rpcgss sunrpc ipv6 crc_ccitt vfat fat joydev iTCO_wdt
>> iTCO_vendor_support mxm_wmi pcspkr sg i2c_i801 i2c_smbus lpc_ich
>> mfd_core shpchp xhci_pci xhci_hcd igb i2c_algo_bit i2c_core ptp
>> pps_core ioatdma dca ipmi_si ipmi_msghandler wmi acpi_cpufreq acpi_pad
>> dm_mod(E) ext4(E) mbcache(E) jbd2(E) sd_mod(E) ahci(E) libahci(E)
>> [last unloaded: scsi_transport_fc]
>> CPU: 9 PID: 3672 Comm: cryptomgr_test Tainted: G OE 4.9.13 #2
>> Hardware name: Supermicro X10DRi/X10DRi, BIOS 2.0 12/28/2015
>> task: ffff88103b418a00 task.stack: ffffc90008a7c000
>> RIP: 0010:[<ffffffff81317c66>] [<ffffffff81317c66>] __list_add+0x26/0xd0
>> RSP: 0018:ffffc90008a7f8c8 EFLAGS: 00010046
>> RAX: 0000000000000000 RBX: ffffc90008a7f920 RCX: 0000000000000001
>> RDX: ffff88103c8b5ef0 RSI: 0000000000000000 RDI: ffffc90008a7f920
>> RBP: ffffc90008a7f8f8 R08: 0000000000000000 R09: ffff8810053200b0
>> R10: ffff88103caf3100 R11: 0000000000000020 R12: ffff88103c8b5ef0
>> R13: 0000000000000000 R14: ffff88103b418a00 R15: 7fffffffffffffff
>> FS: 0000000000000000(0000) GS:ffff88107f440000(0000) knlGS:0000000000000000
>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000000000000000 CR3: 0000000001c07000 CR4: 00000000001406e0
>> Stack:
>> ffffc90008a7f8e8 0000000000000246 ffff88103caf3040 ffff88103c8b5ee0
>> ffff88103c8b5ee8 ffffc90008a7f908 ffffc90008a7f968 ffffffff81654c02
>> 0000000000000001 ffff88103b418a00 ffffffff81097370 0000000000000000
>> Call Trace:
>> [<ffffffff81654c02>] wait_for_completion_interruptible+0xc2/0x130
>> [<ffffffff81097370>] ? try_to_wake_up+0x240/0x240
>> [<ffffffffa02582fb>] drbg_kcapi_sym_ctr+0xeb/0x150 [drbg]
>> [<ffffffffa0259560>] drbg_ctr_update+0x1b0/0x2a0 [drbg]
>> [<ffffffffa0259bd2>] drbg_seed+0x1a2/0x2e0 [drbg]
>> [<ffffffffa025a6ef>] ? drbg_init_sym_kernel+0x13f/0x200 [drbg]
>> [<ffffffffa025aa62>] drbg_instantiate+0x52/0x1e0 [drbg]
>> [<ffffffff811ca2ee>] ? __kmalloc+0xee/0x1d0
>> [<ffffffff812a873d>] ? crypto_create_tfm+0x3d/0xd0
>> [<ffffffffa025acbc>] drbg_kcapi_seed+0xcc/0x118 [drbg]
>> [<ffffffff812a87a1>] ? crypto_create_tfm+0xa1/0xd0
>> [<ffffffff812bb48d>] crypto_rng_reset+0x5d/0x80
>> [<ffffffff812b5197>] drbg_cavs_test+0xf7/0x370
>> [<ffffffff810a3018>] ? dequeue_task_fair+0x68/0x420
>> [<ffffffff8109ccd5>] ? pick_next_task_idle+0x45/0x50
>> [<ffffffff812b547b>] alg_test_drbg+0x6b/0xa0
>> [<ffffffff812b18d5>] alg_test+0x145/0x350
>> [<ffffffff812b0ad0>] ? cryptomgr_probe+0xd0/0xd0
>> [<ffffffff812b0ad0>] ? cryptomgr_probe+0xd0/0xd0
>> [<ffffffff812b0b15>] cryptomgr_test+0x45/0x50
>> [<ffffffff8108a5ed>] kthread+0xcd/0xf0
>> [<ffffffff8109503e>] ? schedule_tail+0x1e/0xc0
>> [<ffffffff8108a520>] ? __kthread_init_worker+0x40/0x40
>> [<ffffffff81657bd2>] ret_from_fork+0x22/0x30
>> Code: 00 00 00 00 00 55 48 89 e5 48 83 ec 30 48 89 5d e8 4c 89 65 f0
>> 48 89 fb 4c 89 6d f8 4c 8b 42 08 49 89 f5 49 89 d4 49 39 f0 75 31 <4d>
>> 8b 45 00 4d 39 c4 75 6f 4c 39 e3 74 45 4c 39 eb 74 40 49 89
>> RIP [<ffffffff81317c66>] __list_add+0x26/0xd0
>> RSP <ffffc90008a7f8c8>
>> CR2: 0000000000000000
>> ---[ end trace fbf11c880e8c4c52 ]---
>
> Ciao
> Stephan