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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, Pan Bian <bianpan2016@163.com>,
        Christoph Hellwig <hch@lst.de>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Bob Peterson <rpeterso@redhat.com>
Subject: [PATCH 4.20 33/65] gfs2: Get rid of potential double-freeing in gfs2_create_inode
Date:   Fri, 11 Jan 2019 15:15:19 +0100
Message-Id: <20190111131100.894748678@linuxfoundation.org>
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References: <20190111131055.331350141@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andreas Gruenbacher <agruenba@redhat.com>

commit 6ff9b09e00a441599f3aacdf577254455a048bc9 upstream.

In gfs2_create_inode, after setting and releasing the acl / default_acl, the
acl / default_acl pointers are not set to NULL as they should be.  In that
state, when the function reaches label fail_free_acls, gfs2_create_inode will
try to release the same acls again.

Fix that by setting the pointers to NULL after releasing the acls.  Slightly
simplify the logic.  Also, posix_acl_release checks for NULL already, so
there is no need to duplicate those checks here.

Fixes: e01580bf9e4d ("gfs2: use generic posix ACL infrastructure")
Reported-by: Pan Bian <bianpan2016@163.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/gfs2/inode.c |   18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -744,17 +744,19 @@ static int gfs2_create_inode(struct inod
 			       the gfs2 structures. */
 	if (default_acl) {
 		error = __gfs2_set_acl(inode, default_acl, ACL_TYPE_DEFAULT);
+		if (error)
+			goto fail_gunlock3;
 		posix_acl_release(default_acl);
+		default_acl = NULL;
 	}
 	if (acl) {
-		if (!error)
-			error = __gfs2_set_acl(inode, acl, ACL_TYPE_ACCESS);
+		error = __gfs2_set_acl(inode, acl, ACL_TYPE_ACCESS);
+		if (error)
+			goto fail_gunlock3;
 		posix_acl_release(acl);
+		acl = NULL;
 	}
 
-	if (error)
-		goto fail_gunlock3;
-
 	error = security_inode_init_security(&ip->i_inode, &dip->i_inode, name,
 					     &gfs2_initxattrs, NULL);
 	if (error)
@@ -789,10 +791,8 @@ fail_free_inode:
 	}
 	gfs2_rsqa_delete(ip, NULL);
 fail_free_acls:
-	if (default_acl)
-		posix_acl_release(default_acl);
-	if (acl)
-		posix_acl_release(acl);
+	posix_acl_release(default_acl);
+	posix_acl_release(acl);
 fail_gunlock:
 	gfs2_dir_no_add(&da);
 	gfs2_glock_dq_uninit(ghs);