On 8/15/2012 10:07 AM, Andy Whitcroft wrote: > On Wed, Aug 15, 2012 at 09:59:51AM -0700, Casey Schaufler wrote: >> On 8/15/2012 8:48 AM, Miklos Szeredi wrote: >>> From: Andy Whitcroft <apw@xxxxxxxxxxxxx> >>> >>> When checking permissions on an overlayfs inode we do not take into >>> account either device cgroup restrictions nor security permissions. >>> This allows a user to mount an overlayfs layer over a restricted device >>> directory and by pass those permissions to open otherwise restricted >>> files. >> Why is this a good idea? Either you're not including enough context >> about the conditions under which this can occur, or you're suggesting >> the introduction of a trivial mechanism for bypassing all file access >> controls. This does not seem right. > It is stating that the unprotected case is how things was before this > patch switches us over to __inode_permisssions. The patch is closing > the hole indicated. Well, that's good then. Carry on. > > -apw >>> Switch over to __inode_permissions. >>> >>> Signed-off-by: Andy Whitcroft <apw@xxxxxxxxxxxxx> >>> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx> >>> --- >>> fs/overlayfs/inode.c | 12 +----------- >>> 1 files changed, 1 insertions(+), 11 deletions(-) >>> >>> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c >>> index e854720..f3a534f 100644 >>> --- a/fs/overlayfs/inode.c >>> +++ b/fs/overlayfs/inode.c >>> @@ -100,19 +100,9 @@ int ovl_permission(struct inode *inode, int mask) >>> if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && >>> (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) >>> goto out_dput; >>> - >>> - /* >>> - * Nobody gets write access to an immutable file. >>> - */ >>> - err = -EACCES; >>> - if (IS_IMMUTABLE(realinode)) >>> - goto out_dput; >>> } >>> >>> - if (realinode->i_op->permission) >>> - err = realinode->i_op->permission(realinode, mask); >>> - else >>> - err = generic_permission(realinode, mask); >>> + err = __inode_permission(realinode, mask); >>> out_dput: >>> dput(alias); >>> return err; > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
