linux-kernel - [PATCH 5.2 124/124] vfs: Fix refcounting of filenames in fs

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Message-Id: <20190919214823.713060325@linuxfoundation.org>
Date:   Fri, 20 Sep 2019 00:03:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, David Howells <dhowells@...hat.com>
Subject: [PATCH 5.2 124/124] vfs: Fix refcounting of filenames in fs_parser

From: David Howells <dhowells@...hat.com>

commit 7cdfa44227b0d8842d46a775cebe4311150cb8f2 upstream.

Fix an overput in which filename_lookup() unconditionally drops a ref to
the filename it was given, but this isn't taken account of in the caller,
fs_lookup_param().

Addresses-Coverity-ID: 1443811 ("Use after free")
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/fs_parser.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -264,6 +264,7 @@ int fs_lookup_param(struct fs_context *f
 		return invalf(fc, "%s: not usable as path", param->key);
 	}
 
+	f->refcnt++; /* filename_lookup() drops our ref. */
 	ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
 	if (ret < 0) {
 		errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);