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

Yury Norov
2022-07-11T18:24:58Z

On Mon, Jul 11, 2022 at 9:15 AM Alexander Lobakin
<alexandr.lobakin@intel.com> wrote:
>
> 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))

Would it make sense to check it inside node_online()?

> 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...).

This is definitely a NUMA problem. Bitmap has 2 kernel-wide users:
cpumasks and numa nodes. Both use negative indexes for their
reasons, which is dangerous, as we can see from here, because
bitmaps don't support them and don't handle it properly...

Can you please send a fix dmar_parse_one_rhsa() as you suggested,
so that I'll add the fix before the beginning of next merge window?

Regarding a general path, this is what I'm thinking on (for a while):
- #define NUMA_NO_NODE MAX_NUMNODES;
- stronger typechecking, like you did in your series;
- introduce CONFIG_DEBUG_BITMAP to catch bad arguments
on-the-fly;

I'm working on DEBUG_BITMAP, hopefully submit it for next merge
cycle.

Thanks,
Yury