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

[ Upstream commit 7ca1db21ef8e0e6725b4d25deed1ca196f7efb28 ]

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.

Link: http://lkml.kernel.org/r/20201012042404.2508-1-anant.thazhemadam@gmail.com
Reported-by: syzbot+75d51fe5bf4ebe988518@syzkaller.appspotmail.com
Tested-by: syzbot+75d51fe5bf4ebe988518@syzkaller.appspotmail.com
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index bad27b0ec65d6bef461f699b852b6e2c5f840bd0..33b317a25a2d510f6001d36e1cb00f4614c82241 100644 (file)
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -1013,7 +1013,7 @@ 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) {