[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20221114214649.ecc18c3ee3f74377ce80e66d@kernel.org>
Date: Mon, 14 Nov 2022 21:46:49 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Zheng Yejian <zhengyejian1@...wei.com>
Cc: <rostedt@...dmis.org>, <linux-kernel@...r.kernel.org>,
<linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: Fix potential null-pointer-access of entry in
list 'tr->err_log'
On Mon, 14 Nov 2022 18:46:32 +0800
Zheng Yejian <zhengyejian1@...wei.com> wrote:
> Entries in list 'tr->err_log' will be reused after entry number
> exceed TRACING_LOG_ERRS_MAX.
>
> The cmd string of the to be reused entry will be freed first then
> allocated a new one. If the allocation failed, then the entry will
> still be in list 'tr->err_log' but its 'cmd' field is set to be NULL,
> later access of 'cmd' is risky.
>
> Currently above problem can cause the loss of 'cmd' information of first
> entry in 'tr->err_log'. When execute `cat /sys/kernel/tracing/error_log`,
> reproduce logs like:
> [ 37.495100] trace_kprobe: error: Maxactive is not for kprobe(null) ^
> [ 38.412517] trace_kprobe: error: Maxactive is not for kprobe
> Command: p4:myprobe2 do_sys_openat2
> ^
This looks good to me.
Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
BTW, I'm interested in how did you reproduce it. Did you inject a memory
allocation failure to reproduce it?
Thank you,
>
> Fixes: 1581a884b7ca ("tracing: Remove size restriction on tracing_log_err cmd strings")
> Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
> ---
> kernel/trace/trace.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 47a44b055a1d..5ae776598106 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -7802,6 +7802,7 @@ static struct tracing_log_err *get_tracing_log_err(struct trace_array *tr,
> int len)
> {
> struct tracing_log_err *err;
> + char *cmd;
>
> if (tr->n_err_log_entries < TRACING_LOG_ERRS_MAX) {
> err = alloc_tracing_log_err(len);
> @@ -7810,12 +7811,12 @@ static struct tracing_log_err *get_tracing_log_err(struct trace_array *tr,
>
> return err;
> }
> -
> + cmd = kzalloc(len, GFP_KERNEL);
> + if (!cmd)
> + return ERR_PTR(-ENOMEM);
> err = list_first_entry(&tr->err_log, struct tracing_log_err, list);
> kfree(err->cmd);
> - err->cmd = kzalloc(len, GFP_KERNEL);
> - if (!err->cmd)
> - return ERR_PTR(-ENOMEM);
> + err->cmd = cmd;
> list_del(&err->list);
>
> return err;
> --
> 2.25.1
>
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
Powered by blists - more mailing lists