[PATCH v3] 9p: client_create/destroy: only call trans_mod->close after create

[Dominique Martinet]

destroy code would incorrectly call close() if trans_mod exists after some
hasty code cleanup: we need to make sure we only call close after create

Link: https://lkml.kernel.org/r/20220928214417.1749609-1-asmadeus@xxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/00000000000015ac7905e97ebaed@xxxxxxxxxx
Reported-by: syzbot+67d13108d855f451cafc@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: Leon Romanovsky <leon@xxxxxxxxxx>
Fixes: 3ff51294a055 ("9p: p9_client_create: use p9_client_destroy on failure")
Signed-off-by: Dominique Martinet <asmadeus@xxxxxxxxxxxxx>
---
v1->v2: also reset trans on create error
v2->v3: fix silly compile errors

Sorry for the multiple mails, that's what I get for not even doing basic
tests before talking...

 net/9p/client.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index bfa80f01992e..41e825a8da7c 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -971,6 +971,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 	spin_lock_init(&clnt->lock);
 	idr_init(&clnt->fids);
 	idr_init(&clnt->reqs);
+	clnt->trans = ERR_PTR(-EINVAL);
 
 	err = parse_opts(options, clnt);
 	if (err < 0)
@@ -990,8 +991,14 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 		 clnt, clnt->trans_mod, clnt->msize, clnt->proto_version);
 
 	err = clnt->trans_mod->create(clnt, dev_name, options);
-	if (err)
+	// ensure clnt->trans is initialized to call close() on destroy
+	// if and only if create succeeded
+	if (err < 0) {
+		clnt->trans = ERR_PTR(err);
 		goto out;
+	}
+	if (IS_ERR(clnt->trans))
+		clnt->trans = NULL;
 
 	if (clnt->msize > clnt->trans_mod->maxsize) {
 		clnt->msize = clnt->trans_mod->maxsize;
@@ -1036,7 +1043,7 @@ void p9_client_destroy(struct p9_client *clnt)
 
 	p9_debug(P9_DEBUG_MUX, "clnt %p\n", clnt);
 
-	if (clnt->trans_mod)
+	if (clnt->trans_mod && !IS_ERR(clnt->trans))
 		clnt->trans_mod->close(clnt);
 
 	v9fs_put_trans(clnt->trans_mod);
-- 
2.35.1