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From: Dominique Martinet <asmadeus@codewreck.org>
To: v9fs-developer@lists.sourceforge.net
Cc: Dominique Martinet <dominique.martinet@cea.fr>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	syzkaller-bugs@googlegroups.com,
	Eric Van Hensbergen <ericvh@gmail.com>,
	Latchesar Ionkov <lucho@ionkov.net>
Subject: [PATCH 2/2] 9p: clear dangling pointers in p9stat_free
Date: Tue, 28 Aug 2018 00:48:28 +0200
Message-ID: <1535410108-20650-2-git-send-email-asmadeus@codewreck.org> (raw)
In-Reply-To: <1535410108-20650-1-git-send-email-asmadeus@codewreck.org>

From: Dominique Martinet <dominique.martinet@cea.fr>

p9stat_free is more of a cleanup function than a 'free' function as it
only frees the content of the struct; there are chances of use-after-free
if it is improperly used (e.g. p9stat_free called twice as it used to be
possible to)

Clearing dangling pointers makes the function idempotent and safer to use.

Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Reported-by: syzbot+d4252148d198410b864f@syzkaller.appspotmail.com
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
---
 net/9p/protocol.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index 4a1e1dd30b52..ee32bbf12675 100644
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -46,10 +46,15 @@ p9pdu_writef(struct p9_fcall *pdu, int proto_version, const char *fmt, ...);
 void p9stat_free(struct p9_wstat *stbuf)
 {
 	kfree(stbuf->name);
+	stbuf->name = NULL;
 	kfree(stbuf->uid);
+	stbuf->uid = NULL;
 	kfree(stbuf->gid);
+	stbuf->gid = NULL;
 	kfree(stbuf->muid);
+	stbuf->muid = NULL;
 	kfree(stbuf->extension);
+	stbuf->extension = NULL;
 }
 EXPORT_SYMBOL(p9stat_free);
 
-- 
2.17.1


      reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-26 13:50 KASAN: invalid-free " syzbot
2018-08-27  5:24 ` Dominique Martinet
2018-08-27 14:25   ` Dmitry Vyukov
2018-08-27 22:40     ` Dominique Martinet
2018-08-27 22:48 ` [PATCH 1/2] v9fs_dir_readdir: fix double-free on p9stat_read error Dominique Martinet
2018-08-27 22:48   ` Dominique Martinet [this message]

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