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5970e15dbc
The file locking definitions have lived in fs.h since the dawn of time, but they are only used by a small subset of the source files that include it. Move the file locking definitions to a new header file, and add the appropriate #include directives to the source files that need them. By doing this we trim down fs.h a bit and limit the amount of rebuilding that has to be done when we make changes to the file locking APIs. Reviewed-by: Xiubo Li <xiubli@redhat.com> Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: David Howells <dhowells@redhat.com> Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> Acked-by: Chuck Lever <chuck.lever@oracle.com> Acked-by: Joseph Qi <joseph.qi@linux.alibaba.com> Acked-by: Steve French <stfrench@microsoft.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Jeff Layton <jlayton@kernel.org>
495 lines
15 KiB
C
495 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/fs/attr.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* changes by Thomas Schoebel-Theuer
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*/
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#include <linux/export.h>
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#include <linux/time.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <linux/sched/signal.h>
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#include <linux/capability.h>
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#include <linux/fsnotify.h>
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#include <linux/fcntl.h>
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#include <linux/filelock.h>
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#include <linux/security.h>
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#include <linux/evm.h>
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#include <linux/ima.h>
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#include "internal.h"
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/**
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* setattr_should_drop_sgid - determine whether the setgid bit needs to be
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* removed
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* @mnt_userns: user namespace of the mount @inode was found from
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* @inode: inode to check
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*
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* This function determines whether the setgid bit needs to be removed.
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* We retain backwards compatibility and require setgid bit to be removed
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* unconditionally if S_IXGRP is set. Otherwise we have the exact same
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* requirements as setattr_prepare() and setattr_copy().
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*
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* Return: ATTR_KILL_SGID if setgid bit needs to be removed, 0 otherwise.
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*/
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int setattr_should_drop_sgid(struct user_namespace *mnt_userns,
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const struct inode *inode)
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{
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umode_t mode = inode->i_mode;
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if (!(mode & S_ISGID))
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return 0;
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if (mode & S_IXGRP)
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return ATTR_KILL_SGID;
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if (!in_group_or_capable(mnt_userns, inode,
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i_gid_into_vfsgid(mnt_userns, inode)))
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return ATTR_KILL_SGID;
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return 0;
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}
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/**
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* setattr_should_drop_suidgid - determine whether the set{g,u}id bit needs to
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* be dropped
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* @mnt_userns: user namespace of the mount @inode was found from
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* @inode: inode to check
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*
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* This function determines whether the set{g,u}id bits need to be removed.
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* If the setuid bit needs to be removed ATTR_KILL_SUID is returned. If the
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* setgid bit needs to be removed ATTR_KILL_SGID is returned. If both
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* set{g,u}id bits need to be removed the corresponding mask of both flags is
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* returned.
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*
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* Return: A mask of ATTR_KILL_S{G,U}ID indicating which - if any - setid bits
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* to remove, 0 otherwise.
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*/
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int setattr_should_drop_suidgid(struct user_namespace *mnt_userns,
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struct inode *inode)
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{
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umode_t mode = inode->i_mode;
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int kill = 0;
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/* suid always must be killed */
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if (unlikely(mode & S_ISUID))
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kill = ATTR_KILL_SUID;
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kill |= setattr_should_drop_sgid(mnt_userns, inode);
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if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
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return kill;
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return 0;
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}
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EXPORT_SYMBOL(setattr_should_drop_suidgid);
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/**
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* chown_ok - verify permissions to chown inode
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* @mnt_userns: user namespace of the mount @inode was found from
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* @inode: inode to check permissions on
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* @ia_vfsuid: uid to chown @inode to
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*
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* If the inode has been found through an idmapped mount the user namespace of
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* the vfsmount must be passed through @mnt_userns. This function will then
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* take care to map the inode according to @mnt_userns before checking
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* permissions. On non-idmapped mounts or if permission checking is to be
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* performed on the raw inode simply passs init_user_ns.
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*/
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static bool chown_ok(struct user_namespace *mnt_userns,
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const struct inode *inode, vfsuid_t ia_vfsuid)
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{
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vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
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if (vfsuid_eq_kuid(vfsuid, current_fsuid()) &&
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vfsuid_eq(ia_vfsuid, vfsuid))
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return true;
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if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_CHOWN))
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return true;
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if (!vfsuid_valid(vfsuid) &&
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ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
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return true;
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return false;
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}
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/**
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* chgrp_ok - verify permissions to chgrp inode
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* @mnt_userns: user namespace of the mount @inode was found from
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* @inode: inode to check permissions on
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* @ia_vfsgid: gid to chown @inode to
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*
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* If the inode has been found through an idmapped mount the user namespace of
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* the vfsmount must be passed through @mnt_userns. This function will then
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* take care to map the inode according to @mnt_userns before checking
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* permissions. On non-idmapped mounts or if permission checking is to be
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* performed on the raw inode simply passs init_user_ns.
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*/
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static bool chgrp_ok(struct user_namespace *mnt_userns,
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const struct inode *inode, vfsgid_t ia_vfsgid)
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{
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vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
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vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
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if (vfsuid_eq_kuid(vfsuid, current_fsuid())) {
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if (vfsgid_eq(ia_vfsgid, vfsgid))
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return true;
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if (vfsgid_in_group_p(ia_vfsgid))
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return true;
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}
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if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_CHOWN))
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return true;
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if (!vfsgid_valid(vfsgid) &&
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ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
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return true;
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return false;
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}
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/**
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* setattr_prepare - check if attribute changes to a dentry are allowed
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* @mnt_userns: user namespace of the mount the inode was found from
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* @dentry: dentry to check
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* @attr: attributes to change
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*
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* Check if we are allowed to change the attributes contained in @attr
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* in the given dentry. This includes the normal unix access permission
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* checks, as well as checks for rlimits and others. The function also clears
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* SGID bit from mode if user is not allowed to set it. Also file capabilities
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* and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
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*
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* If the inode has been found through an idmapped mount the user namespace of
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* the vfsmount must be passed through @mnt_userns. This function will then
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* take care to map the inode according to @mnt_userns before checking
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* permissions. On non-idmapped mounts or if permission checking is to be
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* performed on the raw inode simply passs init_user_ns.
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*
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* Should be called as the first thing in ->setattr implementations,
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* possibly after taking additional locks.
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*/
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int setattr_prepare(struct user_namespace *mnt_userns, struct dentry *dentry,
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struct iattr *attr)
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{
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struct inode *inode = d_inode(dentry);
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unsigned int ia_valid = attr->ia_valid;
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/*
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* First check size constraints. These can't be overriden using
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* ATTR_FORCE.
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*/
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if (ia_valid & ATTR_SIZE) {
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int error = inode_newsize_ok(inode, attr->ia_size);
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if (error)
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return error;
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}
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/* If force is set do it anyway. */
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if (ia_valid & ATTR_FORCE)
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goto kill_priv;
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/* Make sure a caller can chown. */
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if ((ia_valid & ATTR_UID) &&
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!chown_ok(mnt_userns, inode, attr->ia_vfsuid))
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return -EPERM;
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/* Make sure caller can chgrp. */
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if ((ia_valid & ATTR_GID) &&
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!chgrp_ok(mnt_userns, inode, attr->ia_vfsgid))
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return -EPERM;
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/* Make sure a caller can chmod. */
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if (ia_valid & ATTR_MODE) {
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vfsgid_t vfsgid;
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if (!inode_owner_or_capable(mnt_userns, inode))
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return -EPERM;
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if (ia_valid & ATTR_GID)
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vfsgid = attr->ia_vfsgid;
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else
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vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
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/* Also check the setgid bit! */
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if (!in_group_or_capable(mnt_userns, inode, vfsgid))
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attr->ia_mode &= ~S_ISGID;
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}
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/* Check for setting the inode time. */
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if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
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if (!inode_owner_or_capable(mnt_userns, inode))
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return -EPERM;
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}
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kill_priv:
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/* User has permission for the change */
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if (ia_valid & ATTR_KILL_PRIV) {
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int error;
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error = security_inode_killpriv(mnt_userns, dentry);
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if (error)
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return error;
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}
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return 0;
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}
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EXPORT_SYMBOL(setattr_prepare);
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/**
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* inode_newsize_ok - may this inode be truncated to a given size
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* @inode: the inode to be truncated
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* @offset: the new size to assign to the inode
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*
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* inode_newsize_ok must be called with i_mutex held.
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*
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* inode_newsize_ok will check filesystem limits and ulimits to check that the
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* new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
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* when necessary. Caller must not proceed with inode size change if failure is
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* returned. @inode must be a file (not directory), with appropriate
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* permissions to allow truncate (inode_newsize_ok does NOT check these
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* conditions).
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*
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* Return: 0 on success, -ve errno on failure
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*/
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int inode_newsize_ok(const struct inode *inode, loff_t offset)
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{
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if (offset < 0)
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return -EINVAL;
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if (inode->i_size < offset) {
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unsigned long limit;
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limit = rlimit(RLIMIT_FSIZE);
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if (limit != RLIM_INFINITY && offset > limit)
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goto out_sig;
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if (offset > inode->i_sb->s_maxbytes)
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goto out_big;
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} else {
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/*
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* truncation of in-use swapfiles is disallowed - it would
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* cause subsequent swapout to scribble on the now-freed
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* blocks.
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*/
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if (IS_SWAPFILE(inode))
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return -ETXTBSY;
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}
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return 0;
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out_sig:
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send_sig(SIGXFSZ, current, 0);
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out_big:
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return -EFBIG;
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}
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EXPORT_SYMBOL(inode_newsize_ok);
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/**
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* setattr_copy - copy simple metadata updates into the generic inode
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* @mnt_userns: user namespace of the mount the inode was found from
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* @inode: the inode to be updated
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* @attr: the new attributes
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*
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* setattr_copy must be called with i_mutex held.
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*
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* setattr_copy updates the inode's metadata with that specified
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* in attr on idmapped mounts. Necessary permission checks to determine
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* whether or not the S_ISGID property needs to be removed are performed with
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* the correct idmapped mount permission helpers.
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* Noticeably missing is inode size update, which is more complex
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* as it requires pagecache updates.
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*
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* If the inode has been found through an idmapped mount the user namespace of
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* the vfsmount must be passed through @mnt_userns. This function will then
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* take care to map the inode according to @mnt_userns before checking
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* permissions. On non-idmapped mounts or if permission checking is to be
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* performed on the raw inode simply passs init_user_ns.
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*
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* The inode is not marked as dirty after this operation. The rationale is
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* that for "simple" filesystems, the struct inode is the inode storage.
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* The caller is free to mark the inode dirty afterwards if needed.
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*/
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void setattr_copy(struct user_namespace *mnt_userns, struct inode *inode,
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const struct iattr *attr)
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{
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unsigned int ia_valid = attr->ia_valid;
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i_uid_update(mnt_userns, attr, inode);
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i_gid_update(mnt_userns, attr, inode);
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if (ia_valid & ATTR_ATIME)
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inode->i_atime = attr->ia_atime;
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if (ia_valid & ATTR_MTIME)
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inode->i_mtime = attr->ia_mtime;
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if (ia_valid & ATTR_CTIME)
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inode->i_ctime = attr->ia_ctime;
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if (ia_valid & ATTR_MODE) {
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umode_t mode = attr->ia_mode;
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if (!in_group_or_capable(mnt_userns, inode,
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i_gid_into_vfsgid(mnt_userns, inode)))
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mode &= ~S_ISGID;
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inode->i_mode = mode;
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}
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}
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EXPORT_SYMBOL(setattr_copy);
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int may_setattr(struct user_namespace *mnt_userns, struct inode *inode,
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unsigned int ia_valid)
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{
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int error;
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if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
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if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
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return -EPERM;
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}
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/*
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* If utimes(2) and friends are called with times == NULL (or both
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* times are UTIME_NOW), then we need to check for write permission
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*/
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if (ia_valid & ATTR_TOUCH) {
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if (IS_IMMUTABLE(inode))
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return -EPERM;
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if (!inode_owner_or_capable(mnt_userns, inode)) {
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error = inode_permission(mnt_userns, inode, MAY_WRITE);
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if (error)
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return error;
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}
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}
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return 0;
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}
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EXPORT_SYMBOL(may_setattr);
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/**
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* notify_change - modify attributes of a filesytem object
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* @mnt_userns: user namespace of the mount the inode was found from
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* @dentry: object affected
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* @attr: new attributes
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* @delegated_inode: returns inode, if the inode is delegated
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*
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* The caller must hold the i_mutex on the affected object.
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*
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* If notify_change discovers a delegation in need of breaking,
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* it will return -EWOULDBLOCK and return a reference to the inode in
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* delegated_inode. The caller should then break the delegation and
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* retry. Because breaking a delegation may take a long time, the
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* caller should drop the i_mutex before doing so.
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*
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* Alternatively, a caller may pass NULL for delegated_inode. This may
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* be appropriate for callers that expect the underlying filesystem not
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* to be NFS exported. Also, passing NULL is fine for callers holding
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* the file open for write, as there can be no conflicting delegation in
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* that case.
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*
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* If the inode has been found through an idmapped mount the user namespace of
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* the vfsmount must be passed through @mnt_userns. This function will then
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* take care to map the inode according to @mnt_userns before checking
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* permissions. On non-idmapped mounts or if permission checking is to be
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* performed on the raw inode simply passs init_user_ns.
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*/
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int notify_change(struct user_namespace *mnt_userns, struct dentry *dentry,
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struct iattr *attr, struct inode **delegated_inode)
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{
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struct inode *inode = dentry->d_inode;
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umode_t mode = inode->i_mode;
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int error;
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struct timespec64 now;
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unsigned int ia_valid = attr->ia_valid;
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WARN_ON_ONCE(!inode_is_locked(inode));
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error = may_setattr(mnt_userns, inode, ia_valid);
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if (error)
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return error;
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if ((ia_valid & ATTR_MODE)) {
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umode_t amode = attr->ia_mode;
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/* Flag setting protected by i_mutex */
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if (is_sxid(amode))
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inode->i_flags &= ~S_NOSEC;
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}
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now = current_time(inode);
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attr->ia_ctime = now;
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if (!(ia_valid & ATTR_ATIME_SET))
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attr->ia_atime = now;
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else
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attr->ia_atime = timestamp_truncate(attr->ia_atime, inode);
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if (!(ia_valid & ATTR_MTIME_SET))
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attr->ia_mtime = now;
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else
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attr->ia_mtime = timestamp_truncate(attr->ia_mtime, inode);
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if (ia_valid & ATTR_KILL_PRIV) {
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error = security_inode_need_killpriv(dentry);
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if (error < 0)
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return error;
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if (error == 0)
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ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV;
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}
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/*
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* We now pass ATTR_KILL_S*ID to the lower level setattr function so
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* that the function has the ability to reinterpret a mode change
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* that's due to these bits. This adds an implicit restriction that
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* no function will ever call notify_change with both ATTR_MODE and
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* ATTR_KILL_S*ID set.
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*/
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if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
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(ia_valid & ATTR_MODE))
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BUG();
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if (ia_valid & ATTR_KILL_SUID) {
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if (mode & S_ISUID) {
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ia_valid = attr->ia_valid |= ATTR_MODE;
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attr->ia_mode = (inode->i_mode & ~S_ISUID);
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}
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}
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if (ia_valid & ATTR_KILL_SGID) {
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if (mode & S_ISGID) {
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if (!(ia_valid & ATTR_MODE)) {
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ia_valid = attr->ia_valid |= ATTR_MODE;
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attr->ia_mode = inode->i_mode;
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}
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attr->ia_mode &= ~S_ISGID;
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}
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}
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if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
|
|
return 0;
|
|
|
|
/*
|
|
* Verify that uid/gid changes are valid in the target
|
|
* namespace of the superblock.
|
|
*/
|
|
if (ia_valid & ATTR_UID &&
|
|
!vfsuid_has_fsmapping(mnt_userns, inode->i_sb->s_user_ns,
|
|
attr->ia_vfsuid))
|
|
return -EOVERFLOW;
|
|
if (ia_valid & ATTR_GID &&
|
|
!vfsgid_has_fsmapping(mnt_userns, inode->i_sb->s_user_ns,
|
|
attr->ia_vfsgid))
|
|
return -EOVERFLOW;
|
|
|
|
/* Don't allow modifications of files with invalid uids or
|
|
* gids unless those uids & gids are being made valid.
|
|
*/
|
|
if (!(ia_valid & ATTR_UID) &&
|
|
!vfsuid_valid(i_uid_into_vfsuid(mnt_userns, inode)))
|
|
return -EOVERFLOW;
|
|
if (!(ia_valid & ATTR_GID) &&
|
|
!vfsgid_valid(i_gid_into_vfsgid(mnt_userns, inode)))
|
|
return -EOVERFLOW;
|
|
|
|
error = security_inode_setattr(mnt_userns, dentry, attr);
|
|
if (error)
|
|
return error;
|
|
error = try_break_deleg(inode, delegated_inode);
|
|
if (error)
|
|
return error;
|
|
|
|
if (inode->i_op->setattr)
|
|
error = inode->i_op->setattr(mnt_userns, dentry, attr);
|
|
else
|
|
error = simple_setattr(mnt_userns, dentry, attr);
|
|
|
|
if (!error) {
|
|
fsnotify_change(dentry, ia_valid);
|
|
ima_inode_post_setattr(mnt_userns, dentry);
|
|
evm_inode_post_setattr(dentry, ia_valid);
|
|
}
|
|
|
|
return error;
|
|
}
|
|
EXPORT_SYMBOL(notify_change);
|