[PATCH net] net: 9p: initialize sun_server.sun_path to have addr's value only when addr is valid

[Anant Thazhemadam]

In p9_fd_create_unix, checking is performed to see if the addr (passed
as an argument) is NULL or not.
However, no check is performed to see if addr is a valid address, i.e.,
it doesn't entirely consist of only 0's.
The initialization of sun_server.sun_path to be equal to this faulty
addr value leads to an uninitialized variable, as detected by KMSAN.
Checking for this (faulty addr) and returning a negative error number
appropriately, resolves this issue.

Reported-by: syzbot+75d51fe5bf4ebe988518@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+75d51fe5bf4ebe988518@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@xxxxxxxxx>
---
 net/9p/trans_fd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index c0762a302162..8f528e783a6c 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -1023,7 +1023,7 @@ p9_fd_create_unix(struct p9_client *client, const char *addr, char *args)
 
 	csocket = NULL;
 
-	if (addr == NULL)
+	if (!addr || !strlen(addr))
 		return -EINVAL;
 
 	if (strlen(addr) >= UNIX_PATH_MAX) {
-- 
2.25.1