* [PATCH bpf] bpf: fix rcu warning in bpf_prog_run_pin_on_cpu()
@ 2021-07-28 17:23 Yonghong Song
2021-07-29 22:10 ` patchwork-bot+netdevbpf
0 siblings, 1 reply; 2+ messages in thread
From: Yonghong Song @ 2021-07-28 17:23 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Andrii Nakryiko, Daniel Borkmann,
kernel-team, syzbot+7ee5c2c09c284495371f
syzbot reported a RCU warning like below:
WARNING: suspicious RCU usage
...
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
task_css_set include/linux/cgroup.h:481 [inline]
task_dfl_cgroup include/linux/cgroup.h:550 [inline]
____bpf_get_current_cgroup_id kernel/bpf/helpers.c:356 [inline]
bpf_get_current_cgroup_id+0x1ce/0x210 kernel/bpf/helpers.c:354
bpf_prog_08c4887f705f20b8+0x10/0x824
bpf_dispatcher_nop_func include/linux/bpf.h:687 [inline]
bpf_prog_run_pin_on_cpu include/linux/filter.h:624 [inline]
bpf_prog_test_run_syscall+0x2cf/0x5f0 net/bpf/test_run.c:954
bpf_prog_test_run kernel/bpf/syscall.c:3207 [inline]
__sys_bpf+0x1993/0x53b0 kernel/bpf/syscall.c:4487
The warning is introduced by Commit 79a7f8bdb159d
("bpf: Introduce bpf_sys_bpf() helper and program type.").
The rcu_read_lock/unlock() is missing when calling
bpf_prog_run_pin_on_cpu().
Previously, bpf_prog_run_pin_on_cpu() is simply BPF_PROG_RUN
macro and if necessary functions using BPF_PROG_RUN all have proper
rcu_read_lock/unlock() protections.
Commit 3c58482a382ba ("bpf: Provide bpf_prog_run_pin_on_cpu() helper")
added bpf_prog_run_pin_on_cpu() helper in order to add
migrate_disable/enable() support.
Commit 79a7f8bdb159d later called bpf_prog_run_pin_on_cpu()
but didn't have rcu_read_lock/unlock() at the callsite which
triggered the reason.
I added rcu lock protection in bpf_prog_test_run_syscall()
which fixed the issue. Alternatively, rcu lock protection
could be added in bpf_prog_test_run_syscall() and some rcu
lock protection in bpf_prog_test_run_syscall() callers
can be removed. I feel the later is a bigger change for
bpf tree. So I picked the simpler solution.
Reported-by: syzbot+7ee5c2c09c284495371f@syzkaller.appspotmail.com
Fixes: 79a7f8bdb159d ("bpf: Introduce bpf_sys_bpf() helper and program type.")
Signed-off-by: Yonghong Song <yhs@fb.com>
---
net/bpf/test_run.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 1cc75c811e24..a350b185d9d2 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -951,7 +951,10 @@ int bpf_prog_test_run_syscall(struct bpf_prog *prog,
goto out;
}
}
+
+ rcu_read_lock();
retval = bpf_prog_run_pin_on_cpu(prog, ctx);
+ rcu_read_unlock();
if (copy_to_user(&uattr->test.retval, &retval, sizeof(u32))) {
err = -EFAULT;
--
2.30.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH bpf] bpf: fix rcu warning in bpf_prog_run_pin_on_cpu()
2021-07-28 17:23 [PATCH bpf] bpf: fix rcu warning in bpf_prog_run_pin_on_cpu() Yonghong Song
@ 2021-07-29 22:10 ` patchwork-bot+netdevbpf
0 siblings, 0 replies; 2+ messages in thread
From: patchwork-bot+netdevbpf @ 2021-07-29 22:10 UTC (permalink / raw)
To: Yonghong Song
Cc: bpf, ast, andrii, daniel, kernel-team, syzbot+7ee5c2c09c284495371f
Hello:
This patch was applied to bpf/bpf.git (refs/heads/master):
On Wed, 28 Jul 2021 10:23:07 -0700 you wrote:
> syzbot reported a RCU warning like below:
> WARNING: suspicious RCU usage
> ...
> Call Trace:
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
> task_css_set include/linux/cgroup.h:481 [inline]
> task_dfl_cgroup include/linux/cgroup.h:550 [inline]
> ____bpf_get_current_cgroup_id kernel/bpf/helpers.c:356 [inline]
> bpf_get_current_cgroup_id+0x1ce/0x210 kernel/bpf/helpers.c:354
> bpf_prog_08c4887f705f20b8+0x10/0x824
> bpf_dispatcher_nop_func include/linux/bpf.h:687 [inline]
> bpf_prog_run_pin_on_cpu include/linux/filter.h:624 [inline]
> bpf_prog_test_run_syscall+0x2cf/0x5f0 net/bpf/test_run.c:954
> bpf_prog_test_run kernel/bpf/syscall.c:3207 [inline]
> __sys_bpf+0x1993/0x53b0 kernel/bpf/syscall.c:4487
>
> [...]
Here is the summary with links:
- [bpf] bpf: fix rcu warning in bpf_prog_run_pin_on_cpu()
https://git.kernel.org/bpf/bpf/c/8118b11cb603
You are awesome, thank you!
--
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2021-07-28 17:23 [PATCH bpf] bpf: fix rcu warning in bpf_prog_run_pin_on_cpu() Yonghong Song
2021-07-29 22:10 ` patchwork-bot+netdevbpf
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