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Date: Wed, 10 Feb 2021 16:51:04 -0500
From: George Kennedy <george.kennedy@...cle.com>
To: Dmitry Vyukov <dvyukov@...gle.com>,
Konrad Rzeszutek Wilk <konrad@...nok.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
kasan-dev <kasan-dev@...glegroups.com>,
Alexander Potapenko <glider@...gle.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>, pjones@...hat.com,
konrad@...nel.org, LKML <linux-kernel@...r.kernel.org>,
Dan Carpenter <dan.carpenter@...cle.com>,
Dhaval Giani <dhaval.giani@...cle.com>
Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in
ibft_init()
On 2/3/2021 2:35 PM, Dmitry Vyukov wrote:
> On Wed, Feb 3, 2021 at 8:29 PM Konrad Rzeszutek Wilk <konrad@...nok.org> wrote:
>> Hey Dmitry, Rafael, George, please see below..
>>
>> On Wed, Jan 27, 2021 at 10:10:07PM +0100, Dmitry Vyukov wrote:
>>> On Wed, Jan 27, 2021 at 9:01 PM George Kennedy
>>> <george.kennedy@...cle.com> wrote:
>>>> Hi Dmitry,
>>>>
>>>> On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
>>>>
>>>> On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
>>>> <konrad.wilk@...cle.com> wrote:
>>>>
>>>> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
>>>>
>>>> During boot of kernel with CONFIG_KASAN the following KASAN false
>>>> positive failure will occur when ibft_init() reads the
>>>> ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
>>>>
>>>> The ACPI iBFT table is not allocated, and the iscsi driver uses
>>>> a pointer to it to calculate checksum, etc. KASAN complains
>>>> about this pointer with use-after-free, which this is not.
>>>>
>>>> Andrey, Alexander, Dmitry,
>>>>
>>>> I think this is the right way for this, but was wondering if you have
>>>> other suggestions?
>>>>
>>>> Thanks!
>>>>
>>>> Hi George, Konrad,
>>>>
>>>> Please provide a sample KASAN report and kernel version to match line numbers.
>>>>
>>>> 5.4.17-2102.200.0.0.20210106_0000
>>>>
>>>> [ 24.413536] iBFT detected.
>>>> [ 24.414074]
>>>> ==================================================================
>>>> [ 24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
>>>> [ 24.407342] Read of size 4 at addr ffff8880be452004 by task swapper/0/1
>>>> [ 24.407342]
>>>> [ 24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>> [ 24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
>>>> [ 24.407342] Call Trace:
>>>> [ 24.407342] dump_stack+0xd4/0x119
>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>> [ 24.407342] print_address_description.constprop.6+0x20/0x220
>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>> [ 24.407342] __kasan_report.cold.9+0x37/0x77
>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>> [ 24.407342] kasan_report+0x14/0x1b
>>>> [ 24.407342] __asan_report_load_n_noabort+0xf/0x11
>>>> [ 24.407342] ibft_init+0x134/0xb8b
>>>> [ 24.407342] ? dmi_sysfs_init+0x1a5/0x1a5
>>>> [ 24.407342] ? dmi_walk+0x72/0x89
>>>> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
>>>> [ 24.407342] ? rvt_init_port+0x110/0x101
>>>> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
>>>> [ 24.407342] do_one_initcall+0xc3/0x44d
>>>> [ 24.407342] ? perf_trace_initcall_level+0x410/0x405
>>>> [ 24.407342] kernel_init_freeable+0x551/0x673
>>>> [ 24.407342] ? start_kernel+0x94b/0x94b
>>>> [ 24.407342] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>> [ 24.407342] ? __kasan_check_write+0x14/0x16
>>>> [ 24.407342] ? rest_init+0xe6/0xe6
>>>> [ 24.407342] kernel_init+0x16/0x1bd
>>>> [ 24.407342] ? rest_init+0xe6/0xe6
>>>> [ 24.407342] ret_from_fork+0x2b/0x36
>>>> [ 24.407342]
>>>> [ 24.407342] The buggy address belongs to the page:
>>>> [ 24.407342] page:ffffea0002f91480 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1
>>>> [ 24.407342] flags: 0xfffffc0000000()
>>>> [ 24.407342] raw: 000fffffc0000000 ffffea0002fca588 ffffea0002fb1a88 0000000000000000
>>>> [ 24.407342] raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
>>>> [ 24.407342] page dumped because: kasan: bad access detected
>>>> [ 24.407342]
>>>> [ 24.407342] Memory state around the buggy address:
>>>> [ 24.407342] ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342] ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342] ^
>>>> [ 24.407342] ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342] ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342]
>>>> ==================================================================
>>>> [ 24.407342] Disabling lock debugging due to kernel taint
>>>> [ 24.451021] Kernel panic - not syncing: panic_on_warn set ...
>>>> [ 24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>> [ 24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
>>>> [ 24.452002] Call Trace:
>>>> [ 24.452002] dump_stack+0xd4/0x119
>>>> [ 24.452002] ? ibft_init+0x102/0xb8b
>>>> [ 24.452002] panic+0x28f/0x6e0
>>>> [ 24.452002] ? __warn_printk+0xe0/0xe0
>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>> [ 24.452002] ? add_taint+0x68/0xb3
>>>> [ 24.452002] ? add_taint+0x68/0xb3
>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>> [ 24.452002] end_report+0x4c/0x54
>>>> [ 24.452002] __kasan_report.cold.9+0x55/0x77
>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>> [ 24.452002] kasan_report+0x14/0x1b
>>>> [ 24.452002] __asan_report_load_n_noabort+0xf/0x11
>>>> [ 24.452002] ibft_init+0x134/0xb8b
>>>> [ 24.452002] ? dmi_sysfs_init+0x1a5/0x1a5
>>>> [ 24.452002] ? dmi_walk+0x72/0x89
>>>> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
>>>> [ 24.452002] ? rvt_init_port+0x110/0x101
>>>> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
>>>> [ 24.452002] do_one_initcall+0xc3/0x44d
>>>> [ 24.452002] ? perf_trace_initcall_level+0x410/0x405
>>>> [ 24.452002] kernel_init_freeable+0x551/0x673
>>>> [ 24.452002] ? start_kernel+0x94b/0x94b
>>>> [ 24.452002] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>> [ 24.452002] ? __kasan_check_write+0x14/0x16
>>>> [ 24.452002] ? rest_init+0xe6/0xe6
>>>> [ 24.452002] kernel_init+0x16/0x1bd
>>>> [ 24.452002] ? rest_init+0xe6/0xe6
>>>> [ 24.452002] ret_from_fork+0x2b/0x36
>>>> [ 24.452002] Dumping ftrace buffer:
>>>> [ 24.452002] ---------------------------------
>>>> [ 24.452002] swapper/-1 1.... 24564337us : rdmaip_init: 2924: rdmaip_init: Active Bonding is DISABLED
>>>> [ 24.452002] ---------------------------------
>>>> [ 24.452002] Kernel Offset: disabled
>>>> [ 24.452002] Rebooting in 1 seconds..
>>>>
>>>> Why does KASAN think the address is freed? For that to happen that
>>>> memory should have been freed. I don't remember any similar false
>>>> positives from KASAN, so this looks a bit suspicious.
>>>>
>>>> I'm not sure why KASAN thinks the address is freed. There are other modules where KASAN/KCOV is disabled on boot.
>>>> Could this be for a similar reason?
>>> Most of these files are disabled because they cause recursion in
>>> instrumentation, or execute too early in bootstrap process (before
>>> kasan_init).
>>>
>>> Somehow the table pointer in ibft_init points to a freed page. I
>>> tracked it down to here:
>>> https://elixir.bootlin.com/linux/v5.4.17/source/drivers/acpi/acpica/tbutils.c#L399
>>> but I can't find where this table_desc->pointer comes from. Perhaps it
>> It is what the BIOS generated. It usually points to some memory
>> location in right under 4GB and the BIOS stashes the DSDT, iBFT, and
>> other tables in there.
>>
>>> uses some allocation method that's not supported by KASAN? However,
>>> it's the only such case that I've seen, so it's a bit weird. Could it
>>> use something like memblock_alloc? Or maybe that page was in fact
>>> freed?... Too bad KASAN does not print free stack for pages, maybe
>>> it's not too hard to do if CONFIG_PAGE_OWNER is enabled...
>> Hm, there is a comment in the acpi_get_table speaking about the
>> requirement of having a acpi_put_table and:
>>
>>
>> * DESCRIPTION: Finds and verifies an ACPI table. Table must be in the
>> * RSDT/XSDT.
>> * Note that an early stage acpi_get_table() call must be paired
>> * with an early stage acpi_put_table() call. otherwise the table
>> * pointer mapped by the early stage mapping implementation may be
>> * erroneously unmapped by the late stage unmapping implementation
>> * in an acpi_put_table() invoked during the late stage.
>> *
>>
>> Which would imply that I should use acpi_put_table in the error path
>> (see below a patch), but also copy the structure instead of depending
>> on ACPI keeping it mapped for me. I think.
> Hi Konrad,
>
> Thanks for looking into this.
> If ACPI unmaps this page, that would perfectly explain the KASAN report.
>
> George, does this patch eliminate the KASAN report for you?
Hi Dmitry,
No luck with the patch. Tried high level bisect instead. Here are the
results:
BUG: KASAN: use-after-free in ibft_init+0x134/0xc49
Bisect status:
v5.11-rc6 Sun Jan 31 13:50:09 2021 -0800 Failed
v5.11-rc1 Sun Dec 27 15:30:22 2020 -0800 Failed
v5.10 Sun Dec 13 14:41:30 2020 -0800 Failed
v5.10-rc6 Sun Nov 29 15:50:50 2020 -0800 Failed
v5.10-rc5 Sun Nov 22 15:36:08 2020 -0800 Failed
v5.10-rc4 Sun Nov 15 16:44:31 2020 -0800 Failed
v5.10-rc3 Sun Nov 8 16:10:16 2020 -0800 Failed
v5.10-rc2 Sun Nov 1 14:43:52 2020 -0800 Failed
v5.10-rc1 Sun Oct 25 15:14:11 2020 -0700 Failed
v5.9 Sun Oct 11 14:15:50 2020 -0700 OK - 10 reboots so far
w/o kasan failure
So, will look at what changed between v5.9 and v5.10-rc1
Failure is intermittent, so takes a lot of retries.
Thank you,
George
>
>
>> CC-ing Rafeal.
>>
>>
>> From c37da50fdfc62cd4f7b23562b55661478c90a17d Mon Sep 17 00:00:00 2001
>> From: Konrad Rzeszutek Wilk <konrad@...nok.org>
>> Date: Tue, 2 Feb 2021 17:28:28 +0000
>> Subject: [PATCH] ibft: Put ibft_addr back
>>
>> Signed-off-by: Konrad Rzeszutek Wilk <konrad@...nok.org>
>> ---
>> drivers/firmware/iscsi_ibft.c | 19 +++++++++++++------
>> 1 file changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/firmware/iscsi_ibft.c b/drivers/firmware/iscsi_ibft.c
>> index 7127a04..2a1a033 100644
>> --- a/drivers/firmware/iscsi_ibft.c
>> +++ b/drivers/firmware/iscsi_ibft.c
>> @@ -811,6 +811,10 @@ static void ibft_cleanup(void)
>> ibft_unregister();
>> iscsi_boot_destroy_kset(boot_kset);
>> }
>> + if (ibft_addr) {
>> + acpi_put_table((struct acpi_table_header *)ibft_addr);
>> + ibft_addr = NULL;
>> + }
>> }
>>
>> static void __exit ibft_exit(void)
>> @@ -835,13 +839,15 @@ static void __init acpi_find_ibft_region(void)
>> {
>> int i;
>> struct acpi_table_header *table = NULL;
>> + acpi_status status;
>>
>> if (acpi_disabled)
>> return;
>>
>> for (i = 0; i < ARRAY_SIZE(ibft_signs) && !ibft_addr; i++) {
>> - acpi_get_table(ibft_signs[i].sign, 0, &table);
>> - ibft_addr = (struct acpi_table_ibft *)table;
>> + status = acpi_get_table(ibft_signs[i].sign, 0, &table);
>> + if (ACPI_SUCCESS(status))
>> + ibft_addr = (struct acpi_table_ibft *)table;
>> }
>> }
>> #else
>> @@ -870,12 +876,13 @@ static int __init ibft_init(void)
>>
>> rc = ibft_check_device();
>> if (rc)
>> - return rc;
>> + goto out_free;
>>
>> boot_kset = iscsi_boot_create_kset("ibft");
>> - if (!boot_kset)
>> - return -ENOMEM;
>> -
>> + if (!boot_kset) {
>> + rc = -ENOMEM;
>> + goto out_free;
>> + }
>> /* Scan the IBFT for data and register the kobjects. */
>> rc = ibft_register_kobjects(ibft_addr);
>> if (rc)
>> --
>> 1.8.3.1
>>
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