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Message-ID: <ZTpTU8-1zn_P22QX@codewreck.org>
Date: Thu, 26 Oct 2023 20:53:55 +0900
From: asmadeus@...ewreck.org
To: Hangyu Hua <hbh25y@...il.com>
Cc: ericvh@...nel.org, lucho@...kov.net, linux_oss@...debyte.com,
davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, jvrao@...ux.vnet.ibm.com, v9fs@...ts.linux.dev,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: 9p: fix possible memory leak in p9_check_errors()
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.
This cannot break anything so I'll push this to -next tomorrow and
submit to Linus next week
> 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@...il.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.
> goto out_err;
> + }
>
> if (p9_is_proto_dotu(c) && ecode < 512)
> err = -ecode;
--
Dominique Martinet | Asmadeus
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