From f19a4050455aad847fb93f18dc1fe502eb60f989 Mon Sep 17 00:00:00 2001
From: Jiri Olsa <jolsa@kernel.org>
Date: Thu, 15 Dec 2022 22:44:29 +0100
Subject: [PATCH] bpf: Do cleanup in bpf_bprintf_cleanup only when needed
Currently we always cleanup/decrement bpf_bprintf_nest_level variable
in bpf_bprintf_cleanup if it's > 0.
There's possible scenario where this could cause a problem, when
bpf_bprintf_prepare does not get bin_args buffer (because num_args is 0)
and following bpf_bprintf_cleanup call decrements bpf_bprintf_nest_level
variable, like:
in task context:
bpf_bprintf_prepare(num_args != 0) increments 'bpf_bprintf_nest_level = 1'
-> first irq :
bpf_bprintf_prepare(num_args == 0)
bpf_bprintf_cleanup decrements 'bpf_bprintf_nest_level = 0'
-> second irq:
bpf_bprintf_prepare(num_args != 0) bpf_bprintf_nest_level = 1
gets same buffer as task context above
Adding check to bpf_bprintf_cleanup and doing the real cleanup only if we
got bin_args data in the first place.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221215214430.1336195-3-jolsa@kernel.org
---
include/linux/bpf.h | 2 +-
kernel/bpf/helpers.c | 16 +++++++++-------
kernel/trace/bpf_trace.c | 6 +++---
3 files changed, 13 insertions(+), 11 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index cc390ba32e707..656879385fbf5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2803,7 +2803,7 @@ struct bpf_bprintf_data {
int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
u32 num_args, struct bpf_bprintf_data *data);
-void bpf_bprintf_cleanup(void);
+void bpf_bprintf_cleanup(struct bpf_bprintf_data *data);
/* the implementation of the opaque uapi struct bpf_dynptr */
struct bpf_dynptr_kern {
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 7dbf6bb72cad8..9cca02e13f2e2 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -784,12 +784,14 @@ static int try_get_fmt_tmp_buf(char **tmp_buf)
return 0;
}
-void bpf_bprintf_cleanup(void)
+void bpf_bprintf_cleanup(struct bpf_bprintf_data *data)
{
- if (this_cpu_read(bpf_bprintf_nest_level)) {
- this_cpu_dec(bpf_bprintf_nest_level);
- preempt_enable();
- }
+ if (!data->bin_args)
+ return;
+ if (WARN_ON_ONCE(this_cpu_read(bpf_bprintf_nest_level) == 0))
+ return;
+ this_cpu_dec(bpf_bprintf_nest_level);
+ preempt_enable();
}
/*
@@ -1021,7 +1023,7 @@ nocopy_fmt:
err = 0;
out:
if (err)
- bpf_bprintf_cleanup();
+ bpf_bprintf_cleanup(data);
return err;
}
@@ -1047,7 +1049,7 @@ BPF_CALL_5(bpf_snprintf, char *, str, u32, str_size, char *, fmt,
err = bstr_printf(str, str_size, fmt, data.bin_args);
- bpf_bprintf_cleanup();
+ bpf_bprintf_cleanup(&data);
return err + 1;
}
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 3e849c3a7cc8e..2129f7c68bb58 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -396,7 +396,7 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
trace_bpf_trace_printk(buf);
raw_spin_unlock_irqrestore(&trace_printk_lock, flags);
- bpf_bprintf_cleanup();
+ bpf_bprintf_cleanup(&data);
return ret;
}
@@ -454,7 +454,7 @@ BPF_CALL_4(bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, args,
trace_bpf_trace_printk(buf);
raw_spin_unlock_irqrestore(&trace_printk_lock, flags);
- bpf_bprintf_cleanup();
+ bpf_bprintf_cleanup(&data);
return ret;
}
@@ -494,7 +494,7 @@ BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
seq_bprintf(m, fmt, data.bin_args);
- bpf_bprintf_cleanup();
+ bpf_bprintf_cleanup(&data);
return seq_has_overflowed(m) ? -EOVERFLOW : 0;
}
--
2.30.2