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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+75d51fe5bf4ebe988518@syzkaller.appspotmail.com,
        Anant Thazhemadam <anant.thazhemadam@gmail.com>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 079/214] net: 9p: initialize sun_server.sun_path to have addrs value only when addr is valid
Date:   Tue,  3 Nov 2020 21:35:27 +0100
Message-Id: <20201103203257.770567375@linuxfoundation.org>
In-Reply-To: <20201103203249.448706377@linuxfoundation.org>
References: <20201103203249.448706377@linuxfoundation.org>
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From: Anant Thazhemadam <anant.thazhemadam@gmail.com>

[ 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>
---
 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 12ecacf0c55fb..60eb9a2b209be 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) {
-- 
2.27.0