linux-kernel - [PATCH] net/9p/client.c: put refcount of trans_mod in error case in parse

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Date:   Fri, 6 Jul 2018 17:42:56 +0800
From:   piaojun <piaojun@...wei.com>
To:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        <ericvh@...il.com>, <rminnich@...dia.gov>, <lucho@...kov.net>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        <v9fs-developer@...ts.sourceforge.net>,
        Jiangyiwen <jiangyiwen@...wei.com>
Subject: [PATCH] net/9p/client.c: put refcount of trans_mod in error case in
 parse_opts()

>From my test, the second mount will fail after umounting successfully.
The reason is that we put refcount of trans_mod in the correct case rather
than the error case in parse_opts() at last. That will cause the refcount
decrease to -1, and when we try to get trans_mod again in
try_module_get(), we could only increase refcount to 0 which will cause
failure as follows:
parse_opts
  v9fs_get_trans_by_name
    try_module_get : return NULL to caller which cause error

So we should put refcount of trans_mod in error case.

Fixes: 9421c3e64137ec ("net/9p/client.c: fix potential refcnt problem of trans module")

Signed-off-by: Jun Piao <piaojun@...wei.com>
---
 net/9p/client.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index 18c5271..5c13431 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -225,7 +225,8 @@ static int parse_opts(char *opts, struct p9_client *clnt)
 	}

 free_and_return:
-	v9fs_put_trans(clnt->trans_mod);
+	if (ret)
+		v9fs_put_trans(clnt->trans_mod);
 	kfree(tmp_options);
 	return ret;
 }
--