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

[Alexander Lobakin]

From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
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@xxxxxxxxx>
> > 
> > 
> > [ 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