Messages in this thread Patch in this message | | | Date | Mon, 31 Aug 2020 08:50:37 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [rcuperf] 4e88ec4a9e: UBSAN:division-overflow_in_arch/x86/include/asm/div64.h |
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On Mon, Aug 31, 2020 at 08:01:22PM +0800, kernel test robot wrote: > Greeting, > > FYI, we noticed the following commit (built with gcc-9): > > commit: 4e88ec4a9eb17527e640b063f79e5b875733eb53 ("rcuperf: Change rcuperf to rcuscale") > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master > > > in testcase: trinity > with following parameters: > > runtime: 300s > > test-description: Trinity is a linux system call fuzz tester. > test-url: http://codemonkey.org.uk/projects/trinity/ > > > on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 8G > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): > > > +---------------------------------------------------------+------------+------------+ > | | 65bd77f554 | 4e88ec4a9e | > +---------------------------------------------------------+------------+------------+ > | boot_successes | 13 | 0 | > | boot_failures | 0 | 14 | > | UBSAN:division-overflow_in_arch/x86/include/asm/div64.h | 0 | 14 | > | error:#[##] | 0 | 14 | > | EIP:main_func.cold | 0 | 14 | > | Kernel_panic-not_syncing:Fatal_exception | 0 | 14 | > +---------------------------------------------------------+------------+------------+ > > > If you fix the issue, kindly add following tag > Reported-by: kernel test robot <lkp@intel.com>
Does the patch below fix this for you?
Thanx, Paul
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commit d301e320e952e2e604d83d9540e52510b0eb3d94 Author: Paul E. McKenney <paulmck@kernel.org> Date: Thu Aug 27 09:58:19 2020 -0700
refscale: Bounds-check module parameters The default value for refscale.nreaders is -1, which results in the code setting the value to three-quarters of the number of CPUs. On single-CPU systems, this results in three-quarters of the value one, which the C language's integer arithmetic rounds to zero. This in turn results in a divide-by-zero error. This commit therefore adds bounds checking to the refscale module parameters, so that if they are less than one, they are set to the value one. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index 952595c..fb5f20d 100644 --- a/kernel/rcu/refscale.c +++ b/kernel/rcu/refscale.c @@ -681,6 +681,12 @@ ref_scale_init(void) // Reader tasks (default to ~75% of online CPUs). if (nreaders < 0) nreaders = (num_online_cpus() >> 1) + (num_online_cpus() >> 2); + if (WARN_ONCE(loops <= 0, "%s: loops = %ld, adjusted to 1\n", __func__, loops)) + loops = 1; + if (WARN_ONCE(nreaders <= 0, "%s: nreaders = %d, adjusted to 1\n", __func__, nreaders)) + nreaders = 1; + if (WARN_ONCE(nruns <= 0, "%s: nruns = %d, adjusted to 1\n", __func__, nruns)) + nruns = 1; reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]), GFP_KERNEL); if (!reader_tasks) {
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