From: Yonghong Song
mainline inclusion
from mainline-v5.13-rc1
commit b910eaaaa4b89976ef02e5d6448f3f73dc671d91
category: bugfix
issue: #I3ZXZF
CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
-------------------------------------------------
Jiri Olsa reported a bug ([1]) in kernel where cgroup local
storage pointer may be NULL in bpf_get_local_storage() helper.
There are two issues uncovered by this bug:
(1). kprobe or tracepoint prog incorrectly sets cgroup local storage
before prog run,
(2). due to change from preempt_disable to migrate_disable,
preemption is possible and percpu storage might be overwritten
by other tasks.
This issue (1) is fixed in [2]. This patch tried to address issue (2).
The following shows how things can go wrong:
task 1: bpf_cgroup_storage_set() for percpu local storage
preemption happens
task 2: bpf_cgroup_storage_set() for percpu local storage
preemption happens
task 1: run bpf program
task 1 will effectively use the percpu local storage setting by task 2
which will be either NULL or incorrect ones.
Instead of just one common local storage per cpu, this patch fixed
the issue by permitting 8 local storages per cpu and each local
storage is identified by a task_struct pointer. This way, we
allow at most 8 nested preemption between bpf_cgroup_storage_set()
and bpf_cgroup_storage_unset(). The percpu local storage slot
is released (calling bpf_cgroup_storage_unset()) by the same task
after bpf program finished running.
bpf_test_run() is also fixed to use the new bpf_cgroup_storage_set()
interface.
The patch is tested on top of [2] with reproducer in [1].
Without this patch, kernel will emit error in 2-3 minutes.
With this patch, after one hour, still no error.
[1] https://lore.kernel.org/bpf/CAKH8qBuXCfUz=w8L+Fj74OaUpbosO29niYwTki7e3Ag044_...
[2] https://lore.kernel.org/bpf/20210309185028.3763817-1-yhs@fb.com
Signed-off-by: Yonghong Song
Signed-off-by: Alexei Starovoitov
Acked-by: Roman Gushchin
Link: https://lore.kernel.org/bpf/20210323055146.3334476-1-yhs@fb.com
Conflicts:
include/linux/bpf.h
net/bpf/test_run.c
Signed-off-by: Pu Lehui
Reviewed-by: Kuohai Xu
Signed-off-by: Chen Jun
Signed-off-by: Yu Changchun
---
include/linux/bpf-cgroup.h | 57 ++++++++++++++++++++++++++++++++------
include/linux/bpf.h | 43 ++++++++++++++++++++++++++--
kernel/bpf/helpers.c | 15 +++++++---
kernel/bpf/local_storage.c | 5 ++--
net/bpf/test_run.c | 6 +++-
5 files changed, 108 insertions(+), 18 deletions(-)
diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index ed71bd1a0825..53f14e8827cc 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -20,14 +20,25 @@ struct bpf_sock_ops_kern;
struct bpf_cgroup_storage;
struct ctl_table;
struct ctl_table_header;
+struct task_struct;
#ifdef CONFIG_CGROUP_BPF
extern struct static_key_false cgroup_bpf_enabled_key;
#define cgroup_bpf_enabled static_branch_unlikely(&cgroup_bpf_enabled_key)
-DECLARE_PER_CPU(struct bpf_cgroup_storage*,
- bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
+#define BPF_CGROUP_STORAGE_NEST_MAX 8
+
+struct bpf_cgroup_storage_info {
+ struct task_struct *task;
+ struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE];
+};
+
+/* For each cpu, permit maximum BPF_CGROUP_STORAGE_NEST_MAX number of tasks
+ * to use bpf cgroup storage simultaneously.
+ */
+DECLARE_PER_CPU(struct bpf_cgroup_storage_info,
+ bpf_cgroup_storage_info[BPF_CGROUP_STORAGE_NEST_MAX]);
#define for_each_cgroup_storage_type(stype) \
for (stype = 0; stype < MAX_BPF_CGROUP_STORAGE_TYPE; stype++)
@@ -156,13 +167,42 @@ static inline enum bpf_cgroup_storage_type cgroup_storage_type(
return BPF_CGROUP_STORAGE_SHARED;
}
-static inline void bpf_cgroup_storage_set(struct bpf_cgroup_storage
- *storage[MAX_BPF_CGROUP_STORAGE_TYPE])
+static inline int bpf_cgroup_storage_set(struct bpf_cgroup_storage
+ *storage[MAX_BPF_CGROUP_STORAGE_TYPE])
{
enum bpf_cgroup_storage_type stype;
+ int i, err = 0;
+
+ preempt_disable();
+ for (i = 0; i < BPF_CGROUP_STORAGE_NEST_MAX; i++) {
+ if (unlikely(this_cpu_read(bpf_cgroup_storage_info[i].task) != NULL))
+ continue;
+
+ this_cpu_write(bpf_cgroup_storage_info[i].task, current);
+ for_each_cgroup_storage_type(stype)
+ this_cpu_write(bpf_cgroup_storage_info[i].storage[stype],
+ storage[stype]);
+ goto out;
+ }
+ err = -EBUSY;
+ WARN_ON_ONCE(1);
+
+out:
+ preempt_enable();
+ return err;
+}
+
+static inline void bpf_cgroup_storage_unset(void)
+{
+ int i;
+
+ for (i = 0; i < BPF_CGROUP_STORAGE_NEST_MAX; i++) {
+ if (unlikely(this_cpu_read(bpf_cgroup_storage_info[i].task) != current))
+ continue;
- for_each_cgroup_storage_type(stype)
- this_cpu_write(bpf_cgroup_storage[stype], storage[stype]);
+ this_cpu_write(bpf_cgroup_storage_info[i].task, NULL);
+ return;
+ }
}
struct bpf_cgroup_storage *
@@ -410,8 +450,9 @@ static inline int cgroup_bpf_prog_query(const union bpf_attr *attr,
return -EINVAL;
}
-static inline void bpf_cgroup_storage_set(
- struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE]) {}
+static inline int bpf_cgroup_storage_set(
+ struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE]) { return 0; }
+static inline void bpf_cgroup_storage_unset(void) {}
static inline int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux,
struct bpf_map *map) { return 0; }
static inline struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c3ccb242d199..39024b7677ea 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1076,6 +1076,38 @@ int bpf_prog_array_copy(struct bpf_prog_array *old_array,
struct bpf_prog *include_prog,
struct bpf_prog_array **new_array);
+/* For BPF_PROG_RUN_ARRAY_FLAGS and __BPF_PROG_RUN_ARRAY,
+ * if bpf_cgroup_storage_set() failed, the rest of programs
+ * will not execute. This should be a really rare scenario
+ * as it requires BPF_CGROUP_STORAGE_NEST_MAX number of
+ * preemptions all between bpf_cgroup_storage_set() and
+ * bpf_cgroup_storage_unset() on the same cpu.
+ */
+#define BPF_PROG_RUN_ARRAY_FLAGS(array, ctx, func, ret_flags) \
+ ({ \
+ struct bpf_prog_array_item *_item; \
+ struct bpf_prog *_prog; \
+ struct bpf_prog_array *_array; \
+ u32 _ret = 1; \
+ u32 func_ret; \
+ migrate_disable(); \
+ rcu_read_lock(); \
+ _array = rcu_dereference(array); \
+ _item = &_array->items[0]; \
+ while ((_prog = READ_ONCE(_item->prog))) { \
+ if (unlikely(bpf_cgroup_storage_set(_item->cgroup_storage))) \
+ break; \
+ func_ret = func(_prog, ctx); \
+ _ret &= (func_ret & 1); \
+ *(ret_flags) |= (func_ret >> 1); \
+ bpf_cgroup_storage_unset(); \
+ _item++; \
+ } \
+ rcu_read_unlock(); \
+ migrate_enable(); \
+ _ret; \
+ })
+
#define __BPF_PROG_RUN_ARRAY(array, ctx, func, check_non_null, set_cg_storage) \
({ \
struct bpf_prog_array_item *_item; \
@@ -1089,9 +1121,14 @@ int bpf_prog_array_copy(struct bpf_prog_array *old_array,
goto _out; \
_item = &_array->items[0]; \
while ((_prog = READ_ONCE(_item->prog))) { \
- if (set_cg_storage) \
- bpf_cgroup_storage_set(_item->cgroup_storage); \
- _ret &= func(_prog, ctx); \
+ if (!set_cg_storage) { \
+ _ret &= func(_prog, ctx); \
+ } else { \
+ if (unlikely(bpf_cgroup_storage_set(_item->cgroup_storage))) \
+ break; \
+ _ret &= func(_prog, ctx); \
+ bpf_cgroup_storage_unset(); \
+ } \
_item++; \
} \
_out: \
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index f7e99bb8c3b6..3bd7fbd8c543 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -372,8 +372,8 @@ const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto = {
};
#ifdef CONFIG_CGROUP_BPF
-DECLARE_PER_CPU(struct bpf_cgroup_storage*,
- bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
+DECLARE_PER_CPU(struct bpf_cgroup_storage_info,
+ bpf_cgroup_storage_info[BPF_CGROUP_STORAGE_NEST_MAX]);
BPF_CALL_2(bpf_get_local_storage, struct bpf_map *, map, u64, flags)
{
@@ -382,10 +382,17 @@ BPF_CALL_2(bpf_get_local_storage, struct bpf_map *, map, u64, flags)
* verifier checks that its value is correct.
*/
enum bpf_cgroup_storage_type stype = cgroup_storage_type(map);
- struct bpf_cgroup_storage *storage;
+ struct bpf_cgroup_storage *storage = NULL;
void *ptr;
+ int i;
- storage = this_cpu_read(bpf_cgroup_storage[stype]);
+ for (i = 0; i < BPF_CGROUP_STORAGE_NEST_MAX; i++) {
+ if (unlikely(this_cpu_read(bpf_cgroup_storage_info[i].task) != current))
+ continue;
+
+ storage = this_cpu_read(bpf_cgroup_storage_info[i].storage[stype]);
+ break;
+ }
if (stype == BPF_CGROUP_STORAGE_SHARED)
ptr = &READ_ONCE(storage->buf)->data[0];
diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index 571bb351ed3b..b139247d2dd3 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -9,10 +9,11 @@
#include
#include
-DEFINE_PER_CPU(struct bpf_cgroup_storage*, bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
-
#ifdef CONFIG_CGROUP_BPF
+DEFINE_PER_CPU(struct bpf_cgroup_storage_info,
+ bpf_cgroup_storage_info[BPF_CGROUP_STORAGE_NEST_MAX]);
+
#include "../cgroup/cgroup-internal.h"
#define LOCAL_STORAGE_CREATE_FLAG_MASK \
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index e7cbd1b4a5e5..72d424a5a142 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -42,13 +42,17 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
migrate_disable();
time_start = ktime_get_ns();
for (i = 0; i < repeat; i++) {
- bpf_cgroup_storage_set(storage);
+ ret = bpf_cgroup_storage_set(storage);
+ if (ret)
+ break;
if (xdp)
*retval = bpf_prog_run_xdp(prog, ctx);
else
*retval = BPF_PROG_RUN(prog, ctx);
+ bpf_cgroup_storage_unset();
+
if (signal_pending(current)) {
ret = -EINTR;
break;
--
2.22.0
