linux-kernel - Re: [PATCH v2] tracing: fix memory leak in tracing_read

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Date:   Mon, 7 Nov 2022 22:17:10 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     wangyufen <wangyufen@...wei.com>
Cc:     <linux-kernel@...r.kernel.org>, <rostedt@...dmis.org>,
        <mhiramat@...nel.org>
Subject: Re: [PATCH v2] tracing: fix memory leak in tracing_read_pipe

On Mon, 7 Nov 2022 19:45:04 +0800
wangyufen <wangyufen@...wei.com> wrote:

> 
> 在 2022/11/7 19:04, Wang Yufen 写道:
> > kmemleak reports this issue:
> >
> > unreferenced object 0xffff888105a18900 (size 128):
> >    comm "test_progs", pid 18933, jiffies 4336275356 (age 22801.766s)
> >    hex dump (first 32 bytes):
> >      25 73 00 90 81 88 ff ff 26 05 00 00 42 01 58 04  %s......&...B.X.
> >      03 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00  ................
> >    backtrace:
> >      [<00000000560143a1>] __kmalloc_node_track_caller+0x4a/0x140
> >      [<000000006af00822>] krealloc+0x8d/0xf0
> >      [<00000000c309be6a>] trace_iter_expand_format+0x99/0x150
> >      [<000000005a53bdb6>] trace_check_vprintf+0x1e0/0x11d0
> >      [<0000000065629d9d>] trace_event_printf+0xb6/0xf0
> >      [<000000009a690dc7>] trace_raw_output_bpf_trace_printk+0x89/0xc0
> >      [<00000000d22db172>] print_trace_line+0x73c/0x1480
> >      [<00000000cdba76ba>] tracing_read_pipe+0x45c/0x9f0
> >      [<0000000015b58459>] vfs_read+0x17b/0x7c0
> >      [<000000004aeee8ed>] ksys_read+0xed/0x1c0
> >      [<0000000063d3d898>] do_syscall_64+0x3b/0x90
> >      [<00000000a06dda7f>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> >
> > iter->fmt alloced in
> >    tracing_read_pipe() -> .. ->trace_iter_expand_format(), but not
> > freed, to fix, add free in tracing_release_pipe()
> Fixes: efbbdaa22bb7 ("tracing: Show real address for trace event arguments")

Oops, good catch!

Cc: stable@...r.kernel.org

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thank you,

> > Signed-off-by: Wang Yufen <wangyufen@...wei.com>
> > ---
> > v1 -> v2: del if (iter->fmt), free iter->fmt directly
> >   kernel/trace/trace.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 47a44b0..f9d98e7 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -6657,6 +6657,7 @@ static int tracing_release_pipe(struct inode *inode, struct file *file)
> >   	mutex_unlock(&trace_types_lock);
> >   
> >   	free_cpumask_var(iter->started);
> > +	kfree(iter->fmt);
> >   	mutex_destroy(&iter->mutex);
> >   	kfree(iter);
> >   


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>