netdev - Re: [PATCH] bpf: fix mem leak in error path of lwt bpf setup

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Message-ID: <9a07d958-a114-072f-0592-b48e0d3c50e5@iogearbox.net>
Date:   Mon, 21 May 2018 22:39:01 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Martin KaFai Lau <kafai@...com>,
        Mathieu Xhonneux <m.xhonneux@...il.com>
Cc:     netdev@...r.kernel.org, alexei.starovoitov@...il.com
Subject: Re: [PATCH] bpf: fix mem leak in error path of lwt bpf setup

On 05/21/2018 07:44 PM, Martin KaFai Lau wrote:
> On Sun, May 20, 2018 at 02:08:57PM +0100, Mathieu Xhonneux wrote:
>> In bpf_parse_prog, if bpf_prog_get_type fails, the function is
>> immediately terminated without freeing the previously allocated
>> prog->name.
>> This patch adds a kfree before the return.
>>
>> Signed-off-by: Mathieu Xhonneux <m.xhonneux@...il.com>
>> ---
>>  net/core/lwt_bpf.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/core/lwt_bpf.c b/net/core/lwt_bpf.c
>> index e7e626fb87bb..e142a7a32e46 100644
>> --- a/net/core/lwt_bpf.c
>> +++ b/net/core/lwt_bpf.c
>> @@ -223,8 +223,10 @@ static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog,
>>  
>>  	fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
>>  	p = bpf_prog_get_type(fd, type);
>> -	if (IS_ERR(p))
>> +	if (IS_ERR(p)) {
>> +		kfree(prog->name);
> I don't think it is needed.
> The caller, "bpf_build_state()", does bpf_destroy_state() during error
> out and it will eventually free up "name".

Agree, it's not needed in lwt/bpf due to call to destructor in error path.

>>  		return PTR_ERR(p);
>> +	}
>>  
>>  	prog->prog = p;
>>  
>> -- 
>> 2.16.1
>>