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SubjectRe: UBSAN: Undefined behaviour in arch/x86/events/intel/p6.c:116:29
On Tue, Nov 26, 2019 at 07:55:08PM +0200, Meelis Roos wrote:
> While testing 5.4 on a Dell D600 (32-bit), I noticed the old UBSAN warnings from p6 perf events.
> I remember having seen these warnings on other p6 era computers too.
>
> [ 2.795167] ================================================================================
> [ 2.795206] UBSAN: Undefined behaviour in arch/x86/events/intel/p6.c:116:29
> [ 2.795235] index 8 is out of range for type 'u64 [8]'
> [ 2.795265] CPU: 0 PID: 1 Comm: swapper Not tainted 5.4.0-03419-g386403a115f9-dirty #18
> [ 2.795266] Hardware name: Dell Computer Corporation Latitude D600 /0X2034, BIOS A16 06/29/2005
> [ 2.795268] Call Trace:
> [ 2.795283] dump_stack+0x16/0x19
> [ 2.795290] ubsan_epilogue+0xb/0x29
> [ 2.795293] __ubsan_handle_out_of_bounds.cold+0x43/0x48
> [ 2.795299] ? sysfs_add_file_mode_ns+0xad/0x180
> [ 2.795304] p6_pmu_event_map+0x3b/0x50
> [ 2.795306] is_visible+0x25/0x30
> [ 2.795308] ? collect_events+0x150/0x150
> [ 2.795310] internal_create_group+0xd8/0x3e0
> [ 2.795312] ? collect_events+0x150/0x150
> [ 2.795314] internal_create_groups.part.0+0x34/0x80
> [ 2.795317] sysfs_create_groups+0x10/0x20
> [ 2.795321] device_add+0x536/0x5a0
> [ 2.795326] ? kvasprintf_const+0x59/0x90
> [ 2.795331] ? kfree_const+0xf/0x30
> [ 2.795334] ? kobject_set_name_vargs+0x6a/0xa0
> [ 2.795338] pmu_dev_alloc+0x8e/0xe0
> [ 2.795344] perf_event_sysfs_init+0x40/0x78
> [ 2.795346] ? stack_map_init+0x17/0x17
> [ 2.795347] do_one_initcall+0x7a/0x1b3
> [ 2.795351] ? do_early_param+0x75/0x75
> [ 2.795354] kernel_init_freeable+0x1ae/0x230
> [ 2.795357] ? rest_init+0x6d/0x6d
> [ 2.795359] kernel_init+0x9/0xf3
> [ 2.795361] ? rest_init+0x6d/0x6d
> [ 2.795363] ret_from_fork+0x2e/0x38
> [ 2.795364] ================================================================================

Does something like so fix it?

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 9a89d98c55bd..f0ab61cd2f68 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1642,9 +1642,12 @@ static struct attribute_group x86_pmu_format_group __ro_after_init = {

ssize_t events_sysfs_show(struct device *dev, struct device_attribute *attr, char *page)
{
- struct perf_pmu_events_attr *pmu_attr = \
+ struct perf_pmu_events_attr *pmu_attr =
container_of(attr, struct perf_pmu_events_attr, attr);
- u64 config = x86_pmu.event_map(pmu_attr->id);
+ u64 config = 0;
+
+ if (pmu_attr->id < x86_pmu.max_events)
+ config = x86_pmu.event_map(pmu_attr->id);

/* string trumps id */
if (pmu_attr->event_str)
\
 
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