From: Florent Revest <revest@chromium.org>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
kpsingh@kernel.org, jackmanb@google.com,
linux-kernel@vger.kernel.org,
Florent Revest <revest@chromium.org>,
kernel test robot <lkp@intel.com>
Subject: [PATCH bpf 2/2] bpf: Avoid using ARRAY_SIZE on an uninitialized pointer
Date: Mon, 17 May 2021 11:28:30 +0200 [thread overview]
Message-ID: <20210517092830.1026418-2-revest@chromium.org> (raw)
In-Reply-To: <20210517092830.1026418-1-revest@chromium.org>
The cppcheck static code analysis reported the following error:
>> helpers.c:713:43: warning: Uninitialized variable: bufs [uninitvar]
if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(bufs->tmp_bufs))) {
^
ARRAY_SIZE is a macro that expands to sizeofs, so bufs is not actually
dereferenced at runtime, and the code is actually safe. But to keep
things tidy, this patch removes the need for a call to ARRAY_SIZE by
extracting the size of the array into a macro. Cppcheck should no longer
be confused and the code ends up being a bit cleaner.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Florent Revest <revest@chromium.org>
---
kernel/bpf/helpers.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 3a5ab614cbb0..73443498d88f 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -698,8 +698,9 @@ static int bpf_trace_copy_string(char *buf, void *unsafe_ptr, char fmt_ptype,
#define MAX_BPRINTF_BUF_LEN 512
/* Support executing three nested bprintf helper calls on a given CPU */
+#define MAX_BPRINTF_NEST_LEVEL 3
struct bpf_bprintf_buffers {
- char tmp_bufs[3][MAX_BPRINTF_BUF_LEN];
+ char tmp_bufs[MAX_BPRINTF_NEST_LEVEL][MAX_BPRINTF_BUF_LEN];
};
static DEFINE_PER_CPU(struct bpf_bprintf_buffers, bpf_bprintf_bufs);
static DEFINE_PER_CPU(int, bpf_bprintf_nest_level);
@@ -711,7 +712,7 @@ static int try_get_fmt_tmp_buf(char **tmp_buf)
preempt_disable();
nest_level = this_cpu_inc_return(bpf_bprintf_nest_level);
- if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(bufs->tmp_bufs))) {
+ if (WARN_ON_ONCE(nest_level > MAX_BPRINTF_NEST_LEVEL)) {
this_cpu_dec(bpf_bprintf_nest_level);
preempt_enable();
return -EBUSY;
--
2.31.1.751.gd2f1c929bd-goog
next prev parent reply other threads:[~2021-05-17 9:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-17 9:28 [PATCH bpf 1/2] bpf: Clarify a bpf_bprintf_prepare macro Florent Revest
2021-05-17 9:28 ` Florent Revest [this message]
2021-05-17 17:54 ` [PATCH bpf 2/2] bpf: Avoid using ARRAY_SIZE on an uninitialized pointer Song Liu
2021-05-17 17:54 ` [PATCH bpf 1/2] bpf: Clarify a bpf_bprintf_prepare macro Song Liu
2021-05-17 18:10 ` patchwork-bot+netdevbpf
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