linux-kernel - Re: [PATCH] tracing/probe: fix memleak in fetch_op

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Date:   Tue, 16 Jun 2020 17:41:06 +0900
From:   Masami Hiramatsu <masami.hiramatsu@...il.com>
To:     Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>
Cc:     rostedt@...dmis.org, mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/probe: fix memleak in fetch_op_data operations

On Mon, 15 Jun 2020 20:00:38 +0530
Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com> wrote:

> kmemleak report:
>     [<57dcc2ca>] __kmalloc_track_caller+0x139/0x2b0
>     [<f1c45d0f>] kstrndup+0x37/0x80
>     [<f9761eb0>] parse_probe_arg.isra.7+0x3cc/0x630
>     [<055bf2ba>] traceprobe_parse_probe_arg+0x2f5/0x810
>     [<655a7766>] trace_kprobe_create+0x2ca/0x950
>     [<4fc6a02a>] create_or_delete_trace_kprobe+0xf/0x30
>     [<6d1c8a52>] trace_run_command+0x67/0x80
>     [<be812cc0>] trace_parse_run_command+0xa7/0x140
>     [<aecfe401>] probes_write+0x10/0x20
>     [<2027641c>] __vfs_write+0x30/0x1e0
>     [<6a4aeee1>] vfs_write+0x96/0x1b0
>     [<3517fb7d>] ksys_write+0x53/0xc0
>     [<dad91db7>] __ia32_sys_write+0x15/0x20
>     [<da347f64>] do_syscall_32_irqs_on+0x3d/0x260
>     [<fd0b7e7d>] do_fast_syscall_32+0x39/0xb0
>     [<ea5ae810>] entry_SYSENTER_32+0xaf/0x102
> 
> Post parse_probe_arg(), the FETCH_OP_DATA operation type is overwritten
> to FETCH_OP_ST_STRING, as a result memory is never freed since
> traceprobe_free_probe_arg() iterates only over SYMBOL and DATA op types
> 
> Setup fetch string operation correctly after fetch_op_data operation.
> 

Oops, Good catch! (I've commented it but not coded...)

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

And,

Fixes: a42e3c4de964 ("tracing/probe: Add immediate string parameter support")
Cc: stable@...r.kernel.org

Thank you!

> Signed-off-by: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>
> ---
>  kernel/trace/trace_probe.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index b8a928e..d2867cc 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -639,8 +639,8 @@ static int traceprobe_parse_probe_arg_body(char *arg, ssize_t *size,
>  			ret = -EINVAL;
>  			goto fail;
>  		}
> -		if ((code->op == FETCH_OP_IMM || code->op == FETCH_OP_COMM) ||
> -		     parg->count) {
> +		if ((code->op == FETCH_OP_IMM || code->op == FETCH_OP_COMM ||
> +		     code->op == FETCH_OP_DATA) || parg->count) {
>  			/*
>  			 * IMM, DATA and COMM is pointing actual address, those
>  			 * must be kept, and if parg->count != 0, this is an
> -- 
> 2.7.4
> 


-- 
Masami Hiramatsu