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Subject[PATCH 3.16 201/305] Btrfs: ensure path name is null terminated at btrfs_control_ioctl
3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Filipe Manana <fdmanana@suse.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).

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/btrfs/super.c | 1 +
1 file changed, 1 insertion(+)

--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1771,6 +1771,7 @@ 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:
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