Revision 72cd652b73dd77df6f26bd450e804ee29232669f authored by Athira Rajeev on 05 September 2022, 14:19:28 UTC, committed by Arnaldo Carvalho de Melo on 06 September 2022, 12:45:23 UTC
The affinity code in "affinity_set" function access array named "sched_cpus". The size for this array is allocated in affinity_setup function which is nothing but value from get_cpu_set_size. This is used to contain the cpumask value for each cpu. While setting bit for each cpu, it calls "set_bit" function which access index in sched_cpus array. If we provide a command-line option to -C which is more than the number of CPU's present in the system, the set_bit could access an array member which is out-of the array size. This is because currently, there is no boundary check for the CPU. This will result in seg fault: <<>> ./perf stat -C 12323431 ls Perf can support 2048 CPUs. Consider raising MAX_NR_CPUS Segmentation fault (core dumped) <<>> Fix this by adding boundary check for the array. After the fix from powerpc system: <<>> ./perf stat -C 12323431 ls 1>out Perf can support 2048 CPUs. Consider raising MAX_NR_CPUS Performance counter stats for 'CPU(s) 12323431': <not supported> msec cpu-clock <not supported> context-switches <not supported> cpu-migrations <not supported> page-faults <not supported> cycles <not supported> instructions <not supported> branches <not supported> branch-misses 0.001192373 seconds time elapsed <<>> Reported-by: Nageswara R Sastry <rnsastry@linux.ibm.com> Signed-off-by: Athira Jajeev <atrajeev@linux.vnet.ibm.com> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Tested-by: Nageswara R Sastry <rnsastry@linux.ibm.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Kajol Jain <kjain@linux.ibm.com> Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: linuxppc-dev@lists.ozlabs.org Link: https://lore.kernel.org/r/20220905141929.7171-1-atrajeev@linux.vnet.ibm.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
1 parent f0c86a2
test_fpu.c
// SPDX-License-Identifier: GPL-2.0+
/*
* Test cases for using floating point operations inside a kernel module.
*
* This tests kernel_fpu_begin() and kernel_fpu_end() functions, especially
* when userland has modified the floating point control registers. The kernel
* state might depend on the state set by the userland thread that was active
* before a syscall.
*
* To facilitate the test, this module registers file
* /sys/kernel/debug/selftest_helpers/test_fpu, which when read causes a
* sequence of floating point operations. If the operations fail, either the
* read returns error status or the kernel crashes.
* If the operations succeed, the read returns "1\n".
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/debugfs.h>
#include <asm/fpu/api.h>
static int test_fpu(void)
{
/*
* This sequence of operations tests that rounding mode is
* to nearest and that denormal numbers are supported.
* Volatile variables are used to avoid compiler optimizing
* the calculations away.
*/
volatile double a, b, c, d, e, f, g;
a = 4.0;
b = 1e-15;
c = 1e-310;
/* Sets precision flag */
d = a + b;
/* Result depends on rounding mode */
e = a + b / 2;
/* Denormal and very large values */
f = b / c;
/* Depends on denormal support */
g = a + c * f;
if (d > a && e > a && g > a)
return 0;
else
return -EINVAL;
}
static int test_fpu_get(void *data, u64 *val)
{
int status = -EINVAL;
kernel_fpu_begin();
status = test_fpu();
kernel_fpu_end();
*val = 1;
return status;
}
DEFINE_DEBUGFS_ATTRIBUTE(test_fpu_fops, test_fpu_get, NULL, "%lld\n");
static struct dentry *selftest_dir;
static int __init test_fpu_init(void)
{
selftest_dir = debugfs_create_dir("selftest_helpers", NULL);
if (!selftest_dir)
return -ENOMEM;
debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL,
&test_fpu_fops);
return 0;
}
static void __exit test_fpu_exit(void)
{
debugfs_remove(selftest_dir);
}
module_init(test_fpu_init);
module_exit(test_fpu_exit);
MODULE_LICENSE("GPL");
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