From: Hangyu Hua <hbh25y@gmail.com>
To: asmadeus@codewreck.org
Cc: ericvh@kernel.org, lucho@ionkov.net, linux_oss@crudebyte.com,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, jvrao@linux.vnet.ibm.com,
v9fs@lists.linux.dev, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: 9p: fix possible memory leak in p9_check_errors()
Date: Fri, 27 Oct 2023 10:41:08 +0800 [thread overview]
Message-ID: <0f6ebc50-06d6-4e3d-b296-1045b0255c8a@gmail.com> (raw)
In-Reply-To: <ZTpTU8-1zn_P22QX@codewreck.org>
On 26/10/2023 19:53, asmadeus@codewreck.org wrote:
>
> Hangyu Hua wrote on Thu, Oct 26, 2023 at 05:23:51PM +0800:
>> When p9pdu_readf is called with "s?d" attribute, it allocates a pointer
>> that will store a string. But when p9pdu_readf() fails while handling "d"
>> then this pointer will not be freed in p9_check_errors.
>
> Right, that sounds correct to me.
>
> Out of curiosity how did you notice this? The leak shouldn't happen with
> any valid server.
I just found that any attributes that require memory allocation are
prone to errors when mixed with ordinary attributes.
>
> This cannot break anything so I'll push this to -next tomorrow and
> submit to Linus next week
Agreed.
>
>> Fixes: ca41bb3e21d7 ("[net/9p] Handle Zero Copy TREAD/RERROR case in !dotl case.")
>
> This commit moves this code a bit, but the p9pdu_readf call predates
> it -- in this case the Fixes tag is probably not useful; this affects
> all maintained kernels.
>
>> Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
>> ---
>> net/9p/client.c | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/9p/client.c b/net/9p/client.c
>> index 86bbc7147fc1..6c7cd765b714 100644
>> --- a/net/9p/client.c
>> +++ b/net/9p/client.c
>> @@ -540,12 +540,15 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
>> return 0;
>>
>> if (!p9_is_proto_dotl(c)) {
>> - char *ename;
>> + char *ename = NULL;
>>
>> err = p9pdu_readf(&req->rc, c->proto_version, "s?d",
>> &ename, &ecode);
>> - if (err)
>> + if (err) {
>> + if (ename != NULL)
>> + kfree(ename);
>
> Don't check for NULL before kfree - kfree does it.
> If that's the only remark you get I can fix it when applying the commit
> on my side.
I get it. I will revise it based on your and Christian's comments and
send a v2.
Thanks,
Hangyu
>
>
>> goto out_err;
>> + }
>>
>> if (p9_is_proto_dotu(c) && ecode < 512)
>> err = -ecode;
>
prev parent reply other threads:[~2023-10-27 2:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-26 9:23 [PATCH] net: 9p: fix possible memory leak in p9_check_errors() Hangyu Hua
2023-10-26 11:53 ` asmadeus
2023-10-26 13:18 ` Christian Schoenebeck
2023-10-27 2:41 ` Hangyu Hua [this message]
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