For kuprobe and tracepoint bpf programs, kernel calls
trace_call_bpf() which calls BPF_PROG_RUN_ARRAY_CHECK()
to run the program array. Currently, BPF_PROG_RUN_ARRAY_CHECK()
also calls bpf_cgroup_storage_set() to set percpu
cgroup local storage with NULL value. This is
due to Commit 394e40a29788 ("bpf: extend bpf_prog_array to store
pointers to the cgroup storage") which modified
__BPF_PROG_RUN_ARRAY() to call bpf_cgroup_storage_set()
and this macro is also used by BPF_PROG_RUN_ARRAY_CHECK().
kuprobe and tracepoint programs are not allowed to call
bpf_get_local_storage() helper hence does not
access percpu cgroup local storage. Let us
change BPF_PROG_RUN_ARRAY_CHECK() not to
modify percpu cgroup local storage.
The issue is observed when I tried to debug [1] where
percpu data is overwritten due to
preempt_disable -> migration_disable
change. This patch does not fix the above issue,
which will be addressed separately.
[1] https://lore.kernel.org/bpf/CAKH8qBuXCfUz=w8L+Fj74OaUpbosO29niYwTki7e3Ag044_aww@xxxxxxxxxxxxxx/T
Cc: Roman Gushchin <guro@xxxxxx>
Fixes: 394e40a29788 ("bpf: extend bpf_prog_array to store pointers to the cgroup storage")
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
include/linux/bpf.h | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c931bc97019d..b037cb698fa6 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1110,7 +1110,7 @@ int bpf_prog_array_copy(struct bpf_prog_array *old_array,
_ret; \
})
-#define __BPF_PROG_RUN_ARRAY(array, ctx, func, check_non_null) \
+#define __BPF_PROG_RUN_ARRAY(array, ctx, func, check_non_null, set_cg_storage) \
({ \
struct bpf_prog_array_item *_item; \
struct bpf_prog *_prog; \
@@ -1123,7 +1123,9 @@ int bpf_prog_array_copy(struct bpf_prog_array *old_array,
goto _out; \
_item = &_array->items[0]; \
while ((_prog = READ_ONCE(_item->prog))) { \
- bpf_cgroup_storage_set(_item->cgroup_storage); \
+ if (set_cg_storage) { \
+ bpf_cgroup_storage_set(_item->cgroup_storage); \
+ } \
_ret &= func(_prog, ctx); \
_item++; \
} \
@@ -1170,10 +1172,10 @@ _out: \
})
#define BPF_PROG_RUN_ARRAY(array, ctx, func) \
- __BPF_PROG_RUN_ARRAY(array, ctx, func, false)
+ __BPF_PROG_RUN_ARRAY(array, ctx, func, false, true)
#define BPF_PROG_RUN_ARRAY_CHECK(array, ctx, func) \
- __BPF_PROG_RUN_ARRAY(array, ctx, func, true)
+ __BPF_PROG_RUN_ARRAY(array, ctx, func, true, false)
#ifdef CONFIG_BPF_SYSCALL
DECLARE_PER_CPU(int, bpf_prog_active);
--
2.24.1
