After applying this patch I'm unable to use perf passing perf_event
again like this:
# perf record -a -e evt=cycles -e
./test_config_map.c/maps.pmu_map.event=evt/ --exclude-perf ls
With -v it output:
...
adding perf_bpf_probe:func_write
adding perf_bpf_probe:func_write to 0x367d6a0
add bpf event perf_bpf_probe:func_write_return and attach bpf program 6
adding perf_bpf_probe:func_write_return
adding perf_bpf_probe:func_write_return to 0x3a7fc40
mmap size 528384B
ERROR: failed to insert value to pmu_map[0]
ERROR: Apply config to BPF failed: Invalid option for map, add -v to see
detail
Opening /sys/kernel/debug/tracing//kprobe_events write=
...
Looks like perf sets attr.inherit for cycles? I'll look into this problem.
Thank you.
On 2015/10/22 6:58, Alexei Starovoitov wrote:
Fix safety checks for bpf_perf_event_read():
- only non-inherited events can be added to perf_event_array map
(do this check statically at map insertion time)
- dynamically check that event is local and !pmu->count
Otherwise buggy bpf program can cause kernel splat.
Fixes: 35578d798400 ("bpf: Implement function bpf_perf_event_read() that get the
selected hardware PMU conuter")
Signed-off-by: Alexei Starovoitov <a...@kernel.org>
---
v1->v2: fix compile in case of !CONFIG_PERF_EVENTS
This patch is on top of
http://patchwork.ozlabs.org/patch/533585/
to avoid conflicts.
Even in the worst case the crash is not possible.
Only warn_on_once, so imo net-next is ok.
kernel/bpf/arraymap.c | 9 +++++----
kernel/events/core.c | 16 ++++++++++------
2 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index e3cfe46b074f..75529cc94304 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -294,10 +294,11 @@ static void *perf_event_fd_array_get_ptr(struct bpf_map
*map, int fd)
if (IS_ERR(attr))
return (void *)attr;
- if (attr->type != PERF_TYPE_RAW &&
- !(attr->type == PERF_TYPE_SOFTWARE &&
- attr->config == PERF_COUNT_SW_BPF_OUTPUT) &&
- attr->type != PERF_TYPE_HARDWARE) {
+ if ((attr->type != PERF_TYPE_RAW &&
+ !(attr->type == PERF_TYPE_SOFTWARE &&
+ attr->config == PERF_COUNT_SW_BPF_OUTPUT) &&
+ attr->type != PERF_TYPE_HARDWARE) ||
+ attr->inherit) {
perf_event_release_kernel(event);
return ERR_PTR(-EINVAL);
}
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 64754bfecd70..0b6333265872 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3258,7 +3258,7 @@ static inline u64 perf_event_count(struct perf_event
*event)
u64 perf_event_read_local(struct perf_event *event)
{
unsigned long flags;
- u64 val;
+ u64 val = -EINVAL;
/*
* Disabling interrupts avoids all counter scheduling (context
@@ -3267,12 +3267,14 @@ u64 perf_event_read_local(struct perf_event *event)
local_irq_save(flags);
/* If this is a per-task event, it must be for current */
- WARN_ON_ONCE((event->attach_state & PERF_ATTACH_TASK) &&
- event->hw.target != current);
+ if ((event->attach_state & PERF_ATTACH_TASK) &&
+ event->hw.target != current)
+ goto out;
/* If this is a per-CPU event, it must be for this CPU */
- WARN_ON_ONCE(!(event->attach_state & PERF_ATTACH_TASK) &&
- event->cpu != smp_processor_id());
+ if (!(event->attach_state & PERF_ATTACH_TASK) &&
+ event->cpu != smp_processor_id())
+ goto out;
/*
* It must not be an event with inherit set, we cannot read
@@ -3284,7 +3286,8 @@ u64 perf_event_read_local(struct perf_event *event)
* It must not have a pmu::count method, those are not
* NMI safe.
*/
- WARN_ON_ONCE(event->pmu->count);
+ if (event->pmu->count)
+ goto out;
/*
* If the event is currently on this CPU, its either a per-task event,
@@ -3295,6 +3298,7 @@ u64 perf_event_read_local(struct perf_event *event)
event->pmu->read(event);
val = local64_read(&event->count);
+out:
local_irq_restore(flags);
return val;
--
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