linux-kernel - [PATCH 4.4 09/91] Btrfs: ensure path name is null terminated at btrfs_control

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Date:   Tue, 11 Dec 2018 16:40:28 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Anand Jain <anand.jain@...cle.com>,
        Filipe Manana <fdmanana@...e.com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 4.4 09/91] Btrfs: ensure path name is null terminated at btrfs_control_ioctl

4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Filipe Manana <fdmanana@...e.com>

commit f505754fd6599230371cb01b9332754ddc104be1 upstream.

We were using the path name received from user space without checking that
it is null terminated. While btrfs-progs is well behaved and does proper
validation and null termination, someone could call the ioctl and pass
a non-null terminated patch, leading to buffer overrun problems in the
kernel.  The ioctl is protected by CAP_SYS_ADMIN.

So just set the last byte of the path to a null character, similar to what
we do in other ioctls (add/remove/resize device, snapshot creation, etc).

CC: stable@...r.kernel.org # 4.4+
Reviewed-by: Anand Jain <anand.jain@...cle.com>
Signed-off-by: Filipe Manana <fdmanana@...e.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2104,6 +2104,7 @@ static long btrfs_control_ioctl(struct f
 	vol = memdup_user((void __user *)arg, sizeof(*vol));
 	if (IS_ERR(vol))
 		return PTR_ERR(vol);
+	vol->name[BTRFS_PATH_NAME_MAX] = '\0';

 	switch (cmd) {
 	case BTRFS_IOC_SCAN_DEV: