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Date: Thu, 9 Nov 2017 12:38:27 -0600
From: Corey Minyard <minyard@....org>
To: Andrew Banman <abanman@....com>
Cc: Dimitri Sivanich <sivanich@....com>,
"Anderson, Russ" <russ.anderson@....com>,
Mike Travis <mike.travis@....com>,
openipmi-developer@...ts.sourceforge.net,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/char/ipmi_si: prevent null deref during module
exit
On 11/09/2017 12:02 PM, Andrew Banman wrote:
> On 11/8/17 2:00 PM, Corey Minyard wrote:
>> On 11/08/2017 11:11 AM, Andrew Banman wrote:
>>> On 11/8/17 11:06 AM, Andrew Banman wrote:
>>>> If there are uninitialized SMIs in the smi_infos list, i.e. with no
>>>> handlers set, then disable_si_irq() in cleanup_smi_one() will hit a null
>>>> pointer dereference when the former attempts to start the check enables
>>>> transaction. Thus, we panic during module exit.
>>> I think this points to a broader problem of holding uninitialized smi_info
>>> structs in smi_infos list. There are many places where handlers and other struct
>>> members are assumed. Maybe a better design would be to remove SMIs from the list
>>> if we have no intention of initializing them?
>>>
>> This begs the question: How did you produce this? From what I can tell,
>> there is no way you can get to this code if you don't have a working and
>> initialized smi_info structure, and that's not the only place this would
>> have to be fixed if it wasn't. So it's not what you assume, I don't think
>> it's an uninitialized smi_info structure on the list.
> My kernel is missing 0944d889a2, wherein the dmi handling moved to a platform
> device. Without this commit the driver discovers both ACPI and SMBIOS records
> but only initializes the former; this is visible in the tracebacks below.
>
> Is there a case for pushing a similar patch to stable releases predating 0944d889a2
> to prevent this crash?
It looks like you are using a Redhat 3.10 kernel. Is that right?
-corey
> Thank you for your time,
>
> Andrew
>
>> As usual with these sorts of things, please send tracebacks and reproduction
>> procedures.
> # dmesg | grep -i ipmi
> [ 14.883554] ipmi message handler version 39.2
> [ 14.905543] ipmi device interface
> [ 14.931149] ipmi_si IPI0001:00: ipmi_si: probing via ACPI
> [ 14.937254] ipmi_si IPI0001:00: [io 0x0ce4-0x0ce6] regsize 1 spacing 1 irq 6
> [ 14.946767] ipmi_si: Adding ACPI-specified bt state machine
> [ 14.954621] IPMI System Interface driver.
> [ 14.975257] ipmi_si: probing via SMBIOS
> [ 14.980446] ipmi_si: SMBIOS: mem 0xce4 regsize 1 spacing 1 irq 6
> [ 14.987163] ipmi_si: Adding SMBIOS-specified bt state machine
> [ 14.996706] ipmi_si: probing via SPMI
> [ 15.002351] ipmi_si: SPMI: io 0xce4 regsize 1 spacing 1 irq 6
> [ 15.010320] ipmi_si: Adding SPMI-specified bt state machine duplicate interface
> [ 15.020056] ipmi_si: Trying ACPI-specified bt state machine at i/o address 0xce4, slave address 0x0, irq 6
> [ 15.066306] ipmi_si IPI0001:00: Using irq 6
> [ 15.077855] IPMI BT: req2rsp=2 secs retries=1
> [ 15.130045] ipmi_si IPI0001:00: Found new BMC (man_id: 0x000000, prod_id: 0x0101, dev_id: 0x20)
> [ 15.140472] ipmi_si IPI0001:00: IPMI bt interface initialized
> # rmmod ipmi_si
> [ 85.492578] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> [ 85.501346] IP: [<ffffffffc027840e>] start_check_enables+0x3e/0x80 [ipmi_si]
> [ 85.509233] PGD 7fb3875067 PUD 7fbc222067 PMD 0
> [ 85.514421] Oops: 0000 [#1] SMP
> [ 85.518056] Modules linked in: xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter dm_mirror dm_region_hash dm_log dm_mod iTCO_wdt iTCO_vendor_support intel_powerclamp coretemp vfat intel_rapl fat iosf_mbi kvm_intel kvm irqbypass crc32_pclmul ghash_clmulni_intel aesni_intel lrw i40e gf128mul glue_helper ablk_helper cryptd ptp pcspkr pps_core joydev sg i2c_i801 shpchp lpc_ich ipmi_si(-) wmi ipmi_devintf ipmi_msghandler nfit libnvdimm acpi_cpufreq nfsd auth_rpcgss nfs_acl lockd numatools(OE) grace hwperf(OE) binfmt_misc sunrpc ip_tables sr_mod cdrom xfs libcrc32c sd_mod crc_t10dif crct10dif_generic mgag200 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect crct10dif_pclmul crct10dif_common sysimgblt crc32c_intel fb_sys_fops ahci ttm libahci uas drm libata usb_storage i2c_core
> [ 85.616799] CPU: 241 PID: 5743 Comm: rmmod Tainted: G OE ------------ 3.10.0-693.el7.x86_64 #1
> [ 85.627674] Hardware name: HPE Superdome Flex/Superdome Flex, BIOS IP147.006.000.137.000.1711022001 11/02/2017
> [ 85.638843] task: ffff887fb8ac6eb0 ti: ffff887ffd30c000 task.ti: ffff887ffd30c000
> [ 85.647200] RIP: 0010:[<ffffffffc027840e>] [<ffffffffc027840e>] start_check_enables+0x3e/0x80 [ipmi_si]
> [ 85.657794] RSP: 0018:ffff887ffd30fea8 EFLAGS: 00010246
> [ 85.663723] RAX: 0000000000000000 RBX: ffff88016930b000 RCX: 0000000000000006
> [ 85.671688] RDX: 0000000000000002 RSI: ffff887ffd30feae RDI: 0000000000000000
> [ 85.679655] RBP: ffff887ffd30fec0 R08: ffff88016930b1a0 R09: 00000001820001fb
> [ 85.687623] R10: 00000000beb72001 R11: ffffea013efadc80 R12: ffffffffc02822c0
> [ 85.695589] R13: 0000000000000800 R14: 0000000001f222b0 R15: 0000000001f22010
> [ 85.703555] FS: 00007fb9a5c10740(0000) GS:ffff887fbea40000(0000) knlGS:0000000000000000
> [ 85.712587] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 85.719002] CR2: 0000000000000010 CR3: 0000007ffd2a5000 CR4: 00000000003407e0
> [ 85.726968] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 85.734936] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [ 85.742904] Stack:
> [ 85.745150] 2f18887ffd30fec0 000000007706aaa0 ffff88016930b000 ffff887ffd30fed8
> [ 85.753456] ffffffffc027ae19 ffffffffc0281ff0 ffff887ffd30fef0 ffffffffc027b9cb
> [ 85.761762] fffffffffffffff5 ffff887ffd30ff78 ffffffff810fe55b 0000000000000000
> [ 85.770063] Call Trace:
> [ 85.772797] [<ffffffffc027ae19>] cleanup_one_si+0x149/0x180 [ipmi_si]
> [ 85.780090] [<ffffffffc027b9cb>] cleanup_ipmi_si+0x6b/0xc0 [ipmi_si]
> [ 85.787293] [<ffffffff810fe55b>] SyS_delete_module+0x19b/0x300
> [ 85.793913] [<ffffffff816b4fc9>] system_call_fastpath+0x16/0x1b
> [ 85.800621] Code: ee 18 c6 45 ef 2f 65 48 8b 04 25 28 00 00 00 48 89 45 f0 31 c0 40 84 f6 75 33 48 8b 47 18 ba 02 00 00 00 48 8b 7f 10 48 8d 75 ee <ff> 50 10 48 8b 45 f0 65 48 33 04 25 28 00 00 00 c7 43 38 05 00
> [ 85.822638] RIP [<ffffffffc027840e>] start_check_enables+0x3e/0x80 [ipmi_si]
> [ 85.830611] RSP <ffff887ffd30fea8>
> [ 85.834504] CR2: 0000000000000010
>
>
> And with debug printks printing out some contents of the struct at the start of
> module exit:
>
> # rmmod ipmi_si; dmesg -c
> [ 1083.527776] smi_info ffff880fbb38f600
> [ 1083.527779] intf_num 0
> [ 1083.527779] intf ffff880fbb800000
> [ 1083.527780] *si_sm ffff880fbb144400
> [ 1083.527780] *handlers ffffffffa051bac0
> [ 1083.527780] si_type 2
>
> [ 1083.527782] smi_info ffff880fbb38f200
> [ 1083.527783] intf_num 0
> [ 1083.527783] intf (null)
> [ 1083.527784] *si_sm (null)
> [ 1083.527785] *handlers (null)
> [ 1083.527786] si_type 2
>
> @@ -3961,6 +3985,15 @@ static void cleanup_ipmi_si(void)
> if (!initialized)
> return;
>
> + list_for_each_entry_safe(e, tmp_e, &smi_infos, link) {
> + pr_crit("%20s %p\n", "smi_info", e);
> + pr_crit("%20s %d\n", "intf_num", e->intf_num);
> + pr_crit("%20s %p\n", "intf", e->intf);
> + pr_crit("%20s %p\n", "*si_sm", e->si_sm);
> + pr_crit("%20s %p\n", "*handlers", e->handlers);
> + pr_crit("%20s %d\n\n", "si_type", e->si_type);
> + }
> +
> #ifdef CONFIG_PCI
> if (pci_registered)
> pci_unregister_driver(&ipmi_pci_driver);
>> If you are removing the module and this happens, there may be a race
>> conditions, but this is the wrong fix. More likely that the structure gets
>> cleaned up and this function is called afterwards.
>>
>> -corey
>>
>>> Andrew
>>>
>>>> Avoid panicking when there are uninitialized SMIs by checking for a handler
>>>> pointer before starting the check enables transaction.
>>>>
>>>> Signed-off-by: Andrew Banman <abanman@....com>
>>>> ---
>>>> drivers/char/ipmi/ipmi_si_intf.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
>>>> index cb5719e..6c0b1b3 100644
>>>> --- a/drivers/char/ipmi/ipmi_si_intf.c
>>>> +++ b/drivers/char/ipmi/ipmi_si_intf.c
>>>> @@ -442,7 +442,7 @@ static void start_check_enables(struct smi_info
>>>> *smi_info, bool start_timer)
>>>>
>>>> if (start_timer)
>>>> start_new_msg(smi_info, msg, 2);
>>>> - else
>>>> + else if (smi_info->handlers)
>>>> smi_info->handlers->start_transaction(smi_info->si_sm, msg, 2);
>>>> smi_info->si_state = SI_CHECKING_ENABLES;
>>>> }
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