From 073931017b49d9458aa351605b43a7e34598caef Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Mon, 19 Sep 2016 17:39:09 +0200 Subject: posix_acl: Clear SGID bit when setting file permissions When file permissions are modified via chmod(2) and the user is not in the owning group or capable of CAP_FSETID, the setgid bit is cleared in inode_change_ok(). Setting a POSIX ACL via setxattr(2) sets the file permissions as well as the new ACL, but doesn't clear the setgid bit in a similar way; this allows to bypass the check in chmod(2). Fix that. References: CVE-2016-7097 Reviewed-by: Christoph Hellwig Reviewed-by: Jeff Layton Signed-off-by: Jan Kara Signed-off-by: Andreas Gruenbacher --- fs/btrfs/acl.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'fs/btrfs/acl.c') diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c index 53bb7af4e5f0..247b8dfaf6e5 100644 --- a/fs/btrfs/acl.c +++ b/fs/btrfs/acl.c @@ -79,11 +79,9 @@ static int __btrfs_set_acl(struct btrfs_trans_handle *trans, case ACL_TYPE_ACCESS: name = XATTR_NAME_POSIX_ACL_ACCESS; if (acl) { - ret = posix_acl_equiv_mode(acl, &inode->i_mode); - if (ret < 0) + ret = posix_acl_update_mode(inode, &inode->i_mode, &acl); + if (ret) return ret; - if (ret == 0) - acl = NULL; } ret = 0; break; -- cgit v1.2.3