Re: [bitops] 0e862838f2: BUG:KASAN:wild-memory-access_in_dmar_parse_one_rhsa

Alexander Lobakin
2022-07-11T16:15:26Z

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: Fri, 8 Jul 2022 15:17:40 +0300

> On Thu, Jul 07, 2022 at 10:10:20PM +0800, kernel test robot wrote:
> >
> > (please be noted we reported
> > "[bitops] 001bea109d: BUG:KASAN:wild-memory-access_in_dmar_parse_one_rhsa"
> > on
> > https://lore.kernel.org/all/YrnGLtDXAveqXGok@xsang-OptiPlex-9020/
> > now we noticed this commit has already been merged into linux-next/master,
> > and the issue is still existing. report again FYI)
> >
> > Greeting,
> >
> > FYI, we noticed the following commit (built with gcc-11):
> >
> > commit: 0e862838f290147ea9c16db852d8d494b552d38d ("bitops: unify non-atomic bitops prototypes across architectures")
> > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> >
> > in testcase: xfstests
> > version: xfstests-x86_64-c1144bf-1_20220627
> > with following parameters:
> >
> > disk: 2pmem
> > fs: ext4
> > test: ext4-dax
> > ucode: 0x700001c
> >
> > test-description: xfstests is a regression test suite for xfs and other files ystems.
> > test-url: git://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git
> >
> >
> > on test machine: 16 threads 1 sockets Intel(R) Xeon(R) CPU D-1541 @ 2.10GHz with 48G memory
> >
> > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> >
> >
> >
> > If you fix the issue, kindly add following tag
> > Reported-by: kernel test robot <oliver.sang@intel.com>
> >
> >
> > [ 4.668325][ T0] BUG: KASAN: wild-memory-access in dmar_parse_one_rhsa (arch/x86/include/asm/bitops.h:214 arch/x86/include/asm/bitops.h:226 include/asm-generic/bitops/instrumented-non-atomic.h:142 include/linux/nodemask.h:415 drivers/iommu/intel/dmar.c:497)
> > [ 4.676149][ T0] Read of size 8 at addr 1fffffff85115558 by task swapper/0/0
> > [ 4.683454][ T0]
> > [ 4.685638][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.19.0-rc3-00004-g0e862838f290 #1
> > [ 4.694331][ T0] Hardware name: Supermicro SYS-5018D-FN4T/X10SDV-8C-TLN4F, BIOS 1.1 03/02/2016
> > [ 4.703196][ T0] Call Trace:
> > [ 4.706334][ T0] <TASK>
> > [ 4.709133][ T0] ? dmar_parse_one_rhsa (arch/x86/include/asm/bitops.h:214 arch/x86/include/asm/bitops.h:226 include/asm-generic/bitops/instrumented-non-atomic.h:142 include/linux/nodemask.h:415 drivers/iommu/intel/dmar.c:497)
> > [ 4.714272][ T0] dump_stack_lvl (lib/dump_stack.c:107 (discriminator 1))
> > [ 4.718632][ T0] kasan_report (mm/kasan/report.c:162 mm/kasan/report.c:493)
> > [ 4.722903][ T0] ? dmar_parse_one_rhsa (arch/x86/include/asm/bitops.h:214 arch/x86/include/asm/bitops.h:226 include/asm-generic/bitops/instrumented-non-atomic.h:142 include/linux/nodemask.h:415 drivers/iommu/intel/dmar.c:497)
> > [ 4.728042][ T0] kasan_check_range (mm/kasan/generic.c:190)
> > [ 4.732750][ T0] dmar_parse_one_rhsa (arch/x86/include/asm/bitops.h:214 arch/x86/include/asm/bitops.h:226 include/asm-generic/bitops/instrumented-non-atomic.h:142 include/linux/nodemask.h:415 drivers/iommu/intel/dmar.c:497)
> > [ 4.737715][ T0] dmar_walk_remapping_entries (drivers/iommu/intel/dmar.c:609)
> > [ 4.743375][ T0] parse_dmar_table (drivers/iommu/intel/dmar.c:671)
> > [ 4.748079][ T0] ? dmar_table_detect (drivers/iommu/intel/dmar.c:633)
> > [ 4.752872][ T0] ? dmar_free_dev_scope (drivers/iommu/intel/dmar.c:408)
> > [ 4.758010][ T0] ? init_dmars (drivers/iommu/intel/iommu.c:3359)
> > [ 4.762370][ T0] ? iommu_resume (drivers/iommu/intel/iommu.c:3419)
> > [ 4.766903][ T0] ? dmar_walk_dsm_resource+0x300/0x300
> > [ 4.772909][ T0] ? dmar_acpi_insert_dev_scope (drivers/iommu/intel/dmar.c:466)
> > [ 4.778655][ T0] ? dmar_check_one_atsr (drivers/iommu/intel/iommu.c:3521)
> > [ 4.783795][ T0] dmar_table_init (drivers/iommu/intel/dmar.c:846)
> > [ 4.788239][ T0] intel_prepare_irq_remapping (drivers/iommu/intel/irq_remapping.c:742)
> > [ 4.793811][ T0] irq_remapping_prepare (drivers/iommu/irq_remapping.c:102)
> > [ 4.798778][ T0] enable_IR_x2apic (arch/x86/kernel/apic/apic.c:1928)
> > [ 4.803395][ T0] default_setup_apic_routing (arch/x86/kernel/apic/probe_64.c:25 (discriminator 1))
> > [ 4.808883][ T0] apic_intr_mode_init (arch/x86/kernel/apic/apic.c:1446)
> > [ 4.813761][ T0] x86_late_time_init (arch/x86/kernel/time.c:101)
> > [ 4.818467][ T0] start_kernel (init/main.c:1101)
> > [ 4.822827][ T0] secondary_startup_64_no_verify (arch/x86/kernel/head_64.S:358)
>
> Seems like related to nodemask APIs.

It points to arch_test_bit() (node_online() -> test_bit()),
converted from a macro to a function, more precisely, to
variable_test_bit(), which I didn't touch.

...oh ok I got it!

pxm_to_node() can return %NUMA_NO_NODE which equals to -1. The
mentioned commit converts the macro to the function which now takes
`unsigned long` as @nr (bit number). So I guess it gets converted to
%ULONG_MAX - 1.

Now the question is: what should a bitop do if we have negative bit
number? Because there are 2 solutions:

1. (I prefer it) A caller must check that bitop arguments are valid.
UB for negative (== too big) bit numbers.
dmar_parse_one_rhsa() must be fixed so that it will check return
value of pxm_to_node():

int node = pxm_to_node(rhsa->proximity_domain);

- if (!node_online(node))
+ if (node != NUMA_NO_NODE && !node_online(node))
node = NUMA_NO_NODE;

2. My code is broken, I shouldn't change `long` to `unsigned long`
or should change it for {constant,variable}_test_bit() as well
or do something else and let it behave as it was previously
(it wasn't crashing probably due to a good luck or...).

>
> --
> With Best Regards,
> Andy Shevchenko

Thanks,
Olek