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bpf: Do not disable preemption in bpf_test_run().

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The timer mode is initialized to NO_PREEMPT mode by default,
this disables preemption and force execution in atomic context
causing issue on PREEMPT_RT configurations when invoking
spin_lock_bh(), leading to the following warning:

BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6107, name: syz.0.17
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 1
Preemption disabled at:
[<ffffffff891fce58>] bpf_test_timer_enter+0xf8/0x140 net/bpf/test_run.c:42

Fix this, by removing NO_PREEMPT/NO_MIGRATE mode check.
Also, the test timer context no longer needs explicit calls to
migrate_disable()/migrate_enable() with rcu_read_lock()/rcu_read_unlock().
Use helpers rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate()
instead.

Reported-by: syzbot+1f1fbecb9413cdbfbef8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1f1fbecb9413cdbfbef8
Suggested-by: Yonghong Song <yonghong.song@linux.dev>
Suggested-by: Menglong Dong <menglong.dong@linux.dev>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Tested-by: syzbot+1f1fbecb9413cdbfbef8@syzkaller.appspotmail.com
Co-developed-by: Brahmajit Das <listout@listout.xyz>
Signed-off-by: Brahmajit Das <listout@listout.xyz>
Signed-off-by: Sahil Chandna <chandna.sahil@gmail.com>
Link: https://lore.kernel.org/r/20251014185635.10300-1-chandna.sahil@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Sahil Chandna
2025-10-15 00:26:35 +05:30
committed by Alexei Starovoitov
parent f6fddc6df3
commit 7c33e97a6e
1 changed files with 6 additions and 17 deletions
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23
net/bpf/test_run.c
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@@ -29,7 +29,6 @@
#include <trace/events/bpf_test_run.h>
struct bpf_test_timer {
enum { NO_PREEMPT, NO_MIGRATE } mode;
u32 i;
u64 time_start, time_spent;
};
@@ -37,12 +36,7 @@ struct bpf_test_timer {
static void bpf_test_timer_enter(struct bpf_test_timer *t)
__acquires(rcu)
{
rcu_read_lock();
if (t->mode == NO_PREEMPT)
preempt_disable();
else
migrate_disable();
rcu_read_lock_dont_migrate();
t->time_start = ktime_get_ns();
}
@@ -50,12 +44,7 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t)
__releases(rcu)
{
t->time_start = 0;
if (t->mode == NO_PREEMPT)
preempt_enable();
else
migrate_enable();
rcu_read_unlock();
rcu_read_unlock_migrate();
}
static bool bpf_test_timer_continue(struct bpf_test_timer *t, int iterations,
@@ -374,7 +363,7 @@ static int bpf_test_run_xdp_live(struct bpf_prog *prog, struct xdp_buff *ctx,
{
struct xdp_test_data xdp = { .batch_size = batch_size };
struct bpf_test_timer t = { .mode = NO_MIGRATE };
struct bpf_test_timer t = {};
int ret;
if (!repeat)
@@ -404,7 +393,7 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
struct bpf_prog_array_item item = {.prog = prog};
struct bpf_run_ctx *old_ctx;
struct bpf_cg_run_ctx run_ctx;
struct bpf_test_timer t = { NO_MIGRATE };
struct bpf_test_timer t = {};
enum bpf_cgroup_storage_type stype;
int ret;
@@ -1377,7 +1366,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
const union bpf_attr *kattr,
union bpf_attr __user *uattr)
{
struct bpf_test_timer t = { NO_PREEMPT };
struct bpf_test_timer t = {};
u32 size = kattr->test.data_size_in;
struct bpf_flow_dissector ctx = {};
u32 repeat = kattr->test.repeat;
@@ -1445,7 +1434,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kattr,
union bpf_attr __user *uattr)
{
struct bpf_test_timer t = { NO_PREEMPT };
struct bpf_test_timer t = {};
struct bpf_prog_array *progs = NULL;
struct bpf_sk_lookup_kern ctx = {};
u32 repeat = kattr->test.repeat;