linux-kernel - [PATCH v2 2/3] xen/blkback: don't free be structure too early

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 18 May 2017 17:28:48 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc:     konrad.wilk@...cle.com, roger.pau@...rix.com, netwiz@....id.au,
        Juergen Gross <jgross@...e.com>
Subject: [PATCH v2 2/3] xen/blkback: don't free be structure too early

The be structure must nor be freed when freeing the blkif structure
isn't done. Otherwise a use-after-free of be when unmapping the ring
used for communicating with the frontend will occur in case of a
late call of xenblk_disconnect() (e.g. due to an I/O still active
when trying to disconnect).

Signed-off-by: Juergen Gross <jgross@...e.com>
Tested-by: Steven Haigh <netwiz@....id.au>
Acked-by: Roger Pau Monné <roger.pau@...rix.com>
---
 drivers/block/xen-blkback/xenbus.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 998915174bb8..4cdf0490983e 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -315,9 +315,10 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
 
 static void xen_blkif_free(struct xen_blkif *blkif)
 {
-
-	xen_blkif_disconnect(blkif);
+	WARN_ON(xen_blkif_disconnect(blkif));
 	xen_vbd_free(&blkif->vbd);
+	kfree(blkif->be->mode);
+	kfree(blkif->be);
 
 	/* Make sure everything is drained before shutting down */
 	kmem_cache_free(xen_blkif_cachep, blkif);
@@ -514,8 +515,6 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
 		xen_blkif_put(be->blkif);
 	}
 
-	kfree(be->mode);
-	kfree(be);
 	return 0;
 }
 
-- 
2.12.0