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Date: Wed, 2 Dec 2020 10:55:47 +0100 From: Christoph Hellwig <hch@....de> To: Christian Brauner <christian.brauner@...ntu.com> Cc: Christoph Hellwig <hch@....de>, Alexander Viro <viro@...iv.linux.org.uk>, Christoph Hellwig <hch@...radead.org>, linux-fsdevel@...r.kernel.org, John Johansen <john.johansen@...onical.com>, James Morris <jmorris@...ei.org>, Mimi Zohar <zohar@...ux.ibm.com>, Dmitry Kasatkin <dmitry.kasatkin@...il.com>, Stephen Smalley <stephen.smalley.work@...il.com>, Casey Schaufler <casey@...aufler-ca.com>, Arnd Bergmann <arnd@...db.de>, Andreas Dilger <adilger.kernel@...ger.ca>, OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>, Geoffrey Thomas <geofft@...reload.com>, Mrunal Patel <mpatel@...hat.com>, Josh Triplett <josh@...htriplett.org>, Andy Lutomirski <luto@...nel.org>, Theodore Tso <tytso@....edu>, Alban Crequy <alban@...volk.io>, Tycho Andersen <tycho@...ho.ws>, David Howells <dhowells@...hat.com>, James Bottomley <James.Bottomley@...senpartnership.com>, Seth Forshee <seth.forshee@...onical.com>, Stéphane Graber <stgraber@...ntu.com>, Aleksa Sarai <cyphar@...har.com>, Lennart Poettering <lennart@...ttering.net>, "Eric W. Biederman" <ebiederm@...ssion.com>, smbarber@...omium.org, Phil Estes <estesp@...il.com>, Serge Hallyn <serge@...lyn.com>, Kees Cook <keescook@...omium.org>, Todd Kjos <tkjos@...gle.com>, Paul Moore <paul@...l-moore.com>, Jonathan Corbet <corbet@....net>, containers@...ts.linux-foundation.org, fstests@...r.kernel.org, linux-security-module@...r.kernel.org, linux-api@...r.kernel.org, linux-ext4@...r.kernel.org, linux-integrity@...r.kernel.org, selinux@...r.kernel.org Subject: Re: [PATCH v3 04/38] fs: add mount_setattr() On Wed, Dec 02, 2020 at 10:47:51AM +0100, Christoph Hellwig wrote: > On Wed, Dec 02, 2020 at 10:42:18AM +0100, Christian Brauner wrote: > > > > + if (upper_32_bits(attr->attr_set)) > > > > + return -EINVAL; > > > > + if (build_attr_flags(lower_32_bits(attr->attr_set), &kattr->attr_set)) > > > > + return -EINVAL; > > > > + > > > > + if (upper_32_bits(attr->attr_clr)) > > > > + return -EINVAL; > > > > + if (build_attr_flags(lower_32_bits(attr->attr_clr), &kattr->attr_clr)) > > > > + return -EINVAL; > > > > > > What is so magic about the upper and lower 32 bits? > > > > Nothing apart from the fact that they arent't currently valid. I can > > think about reworking these lines. Or do you already have a preferred > > way of doing this in mind? > > Just turn the attr_flags argument to build_attr_flags into a u64 and > the first sanity check there will catch all invalid flags, no matter > where they are places. That should also generate more efficient code. And while we're at it: the check for valid flags in the current code is a little weird, given that build_attr_flags checks for them, and but sys_fsmount also has its own slightly narrower checks. I think it might make sense to split the validity check out of build_attr_flags. E.g. something like: static unsigned int attr_flags_to_mnt_flags(u64 attr_flags) { unsigned int mnt_flags = 0; if (attr_flags & MOUNT_ATTR_RDONLY) mnt_flags |= MNT_READONLY; if (attr_flags & MOUNT_ATTR_NOSUID) mnt_flags |= MNT_NOSUID; if (attr_flags & MOUNT_ATTR_NODEV) mnt_flags |= MNT_NODEV; if (attr_flags & MOUNT_ATTR_NOEXEC) mnt_flags |= MNT_NOEXEC; if (attr_flags & MOUNT_ATTR_NODIRATIME) mnt_flags |= MNT_NODIRATIME; return mnt_flags; } #define MOUNT_SETATTR_VALID_FLAGS \ (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \ MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \ MOUNT_ATTR_IDMAP) static int build_mount_kattr(const struct mount_attr *attr, size_t usize, struct mount_kattr *kattr, unsigned int flags) { ... if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS) return -EINVAL; kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set); kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr); ... }
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