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From:   Fedor Pchelkin <pchelkin@ispras.ru>
To:     Eric Van Hensbergen <ericvh@kernel.org>
Cc:     Fedor Pchelkin <pchelkin@ispras.ru>,
        Latchesar Ionkov <lucho@ionkov.net>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Christian Schoenebeck <linux_oss@crudebyte.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, v9fs@lists.linux.dev,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Alexey Khoroshilov <khoroshilov@ispras.ru>,
        lvc-project@linuxtesting.org
Subject: [PATCH] net: 9p: avoid freeing uninit memory in p9pdu_vreadf
Date:   Tue,  5 Dec 2023 11:05:22 +0300
Message-ID: <20231205080524.6635-1-pchelkin@ispras.ru>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

If an error occurs while processing an array of strings in p9pdu_vreadf
then uninitialized members of *wnames array are freed.

Fix this by iterating over only lower indices of the array.

Found by Linux Verification Center (linuxtesting.org).

Fixes: ace51c4dd2f9 ("9p: add new protocol support code")
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
---
 net/9p/protocol.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index 4e3a2a1ffcb3..d33387e74a66 100644
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -393,6 +393,7 @@ p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
 		case 'T':{
 				uint16_t *nwname = va_arg(ap, uint16_t *);
 				char ***wnames = va_arg(ap, char ***);
+				int i;
 
 				errcode = p9pdu_readf(pdu, proto_version,
 								"w", nwname);
@@ -406,8 +407,6 @@ p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
 				}
 
 				if (!errcode) {
-					int i;
-
 					for (i = 0; i < *nwname; i++) {
 						errcode =
 						    p9pdu_readf(pdu,
@@ -421,9 +420,7 @@ p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
 
 				if (errcode) {
 					if (*wnames) {
-						int i;
-
-						for (i = 0; i < *nwname; i++)
+						while (--i >= 0)
 							kfree((*wnames)[i]);
 					}
 					kfree(*wnames);
-- 
2.43.0