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 <l...@intel.com>
Does the patch below fix this for you?
Thanx, Paul
------------------------------------------------------------------------
commit d301e320e952e2e604d83d9540e52510b0eb3d94
Author: Paul E. McKenney <paul...@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 <l...@intel.com>
Signed-off-by: Paul E. McKenney <paul...@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) {
