Re: [PATCH v2 net-next] bpf: fix bpf_perf_event_read() helper

From: Wangnan (F)
Date: Thu Oct 22 2015 - 01:32:15 EST




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 <ast@xxxxxxxxxx>
---
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) {

This 'if' statement is so complex. What about using a inline function instead?

Thank you.

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