From 805611157d684b46473cd343e0c95e888918d8c4 Mon Sep 17 00:00:00 2001
From: Fedor Pchelkin <pchelkin@ispras.ru>
Date: Wed, 6 Dec 2023 23:09:13 +0300
Subject: [PATCH] net: 9p: avoid freeing uninit memory in p9pdu_vreadf

commit ff49bf1867578f23a5ffdd38f927f6e1e16796c4 upstream.

If some of p9pdu_readf() calls inside case 'T' in p9pdu_vreadf() fails,
the error path is not handled properly. *wnames or members of *wnames
array may be left uninitialized and invalidly freed.

Initialize *wnames to NULL in beginning of case 'T'. Initialize the first
*wnames array element to NULL and nullify the failing *wnames element so
that the error path freeing loop stops on the first NULL element and
doesn't proceed further.

Found by Linux Verification Center (linuxtesting.org).

Fixes: ace51c4dd2f9 ("9p: add new protocol support code")
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Message-ID: <20231206200913.16135-1-pchelkin@ispras.ru>
Cc: stable@vger.kernel.org
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/9p/protocol.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index 4e3a2a1ffcb3..0e6603b1ec90 100644
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -394,6 +394,8 @@ p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
 				uint16_t *nwname = va_arg(ap, uint16_t *);
 				char ***wnames = va_arg(ap, char ***);
 
+				*wnames = NULL;
+
 				errcode = p9pdu_readf(pdu, proto_version,
 								"w", nwname);
 				if (!errcode) {
@@ -403,6 +405,8 @@ p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
 							  GFP_NOFS);
 					if (!*wnames)
 						errcode = -ENOMEM;
+					else
+						(*wnames)[0] = NULL;
 				}
 
 				if (!errcode) {
@@ -414,8 +418,10 @@ p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
 								proto_version,
 								"s",
 								&(*wnames)[i]);
-						if (errcode)
+						if (errcode) {
+							(*wnames)[i] = NULL;
 							break;
+						}
 					}
 				}
 
@@ -423,11 +429,14 @@ p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
 					if (*wnames) {
 						int i;
 
-						for (i = 0; i < *nwname; i++)
+						for (i = 0; i < *nwname; i++) {
+							if (!(*wnames)[i])
+								break;
 							kfree((*wnames)[i]);
+						}
+						kfree(*wnames);
+						*wnames = NULL;
 					}
-					kfree(*wnames);
-					*wnames = NULL;
 				}
 			}
 			break;