drm/panthor: Don't declare a queue blocked if deferred operations are pending

[drm/drm-misc.git] / fs / attr.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/attr.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  changes by Thomas Schoebel-Theuer
 */

#include <linux/export.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/sched/signal.h>
#include <linux/capability.h>
#include <linux/fsnotify.h>
#include <linux/fcntl.h>
#include <linux/filelock.h>
#include <linux/security.h>

/**
 * setattr_should_drop_sgid - determine whether the setgid bit needs to be
 *                            removed
 * @idmap:      idmap of the mount @inode was found from
 * @inode:      inode to check
 *
 * This function determines whether the setgid bit needs to be removed.
 * We retain backwards compatibility and require setgid bit to be removed
 * unconditionally if S_IXGRP is set. Otherwise we have the exact same
 * requirements as setattr_prepare() and setattr_copy().
 *
 * Return: ATTR_KILL_SGID if setgid bit needs to be removed, 0 otherwise.
 */
int setattr_should_drop_sgid(struct mnt_idmap *idmap,
                             const struct inode *inode)
{
        umode_t mode = inode->i_mode;

        if (!(mode & S_ISGID))
                return 0;
        if (mode & S_IXGRP)
                return ATTR_KILL_SGID;
        if (!in_group_or_capable(idmap, inode, i_gid_into_vfsgid(idmap, inode)))
                return ATTR_KILL_SGID;
        return 0;
}
EXPORT_SYMBOL(setattr_should_drop_sgid);

/**
 * setattr_should_drop_suidgid - determine whether the set{g,u}id bit needs to
 *                               be dropped
 * @idmap:      idmap of the mount @inode was found from
 * @inode:      inode to check
 *
 * This function determines whether the set{g,u}id bits need to be removed.
 * If the setuid bit needs to be removed ATTR_KILL_SUID is returned. If the
 * setgid bit needs to be removed ATTR_KILL_SGID is returned. If both
 * set{g,u}id bits need to be removed the corresponding mask of both flags is
 * returned.
 *
 * Return: A mask of ATTR_KILL_S{G,U}ID indicating which - if any - setid bits
 * to remove, 0 otherwise.
 */
int setattr_should_drop_suidgid(struct mnt_idmap *idmap,
                                struct inode *inode)
{
        umode_t mode = inode->i_mode;
        int kill = 0;

        /* suid always must be killed */
        if (unlikely(mode & S_ISUID))
                kill = ATTR_KILL_SUID;

        kill |= setattr_should_drop_sgid(idmap, inode);

        if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
                return kill;

        return 0;
}
EXPORT_SYMBOL(setattr_should_drop_suidgid);

/**
 * chown_ok - verify permissions to chown inode
 * @idmap:      idmap of the mount @inode was found from
 * @inode:      inode to check permissions on
 * @ia_vfsuid:  uid to chown @inode to
 *
 * If the inode has been found through an idmapped mount the idmap of
 * the vfsmount must be passed through @idmap. This function will then
 * take care to map the inode according to @idmap before checking
 * permissions. On non-idmapped mounts or if permission checking is to be
 * performed on the raw inode simply pass @nop_mnt_idmap.
 */
static bool chown_ok(struct mnt_idmap *idmap,
                     const struct inode *inode, vfsuid_t ia_vfsuid)
{
        vfsuid_t vfsuid = i_uid_into_vfsuid(idmap, inode);
        if (vfsuid_eq_kuid(vfsuid, current_fsuid()) &&
            vfsuid_eq(ia_vfsuid, vfsuid))
                return true;
        if (capable_wrt_inode_uidgid(idmap, inode, CAP_CHOWN))
                return true;
        if (!vfsuid_valid(vfsuid) &&
            ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
                return true;
        return false;
}

/**
 * chgrp_ok - verify permissions to chgrp inode
 * @idmap:      idmap of the mount @inode was found from
 * @inode:      inode to check permissions on
 * @ia_vfsgid:  gid to chown @inode to
 *
 * If the inode has been found through an idmapped mount the idmap of
 * the vfsmount must be passed through @idmap. This function will then
 * take care to map the inode according to @idmap before checking
 * permissions. On non-idmapped mounts or if permission checking is to be
 * performed on the raw inode simply pass @nop_mnt_idmap.
 */
static bool chgrp_ok(struct mnt_idmap *idmap,
                     const struct inode *inode, vfsgid_t ia_vfsgid)
{
        vfsgid_t vfsgid = i_gid_into_vfsgid(idmap, inode);
        vfsuid_t vfsuid = i_uid_into_vfsuid(idmap, inode);
        if (vfsuid_eq_kuid(vfsuid, current_fsuid())) {
                if (vfsgid_eq(ia_vfsgid, vfsgid))
                        return true;
                if (vfsgid_in_group_p(ia_vfsgid))
                        return true;
        }
        if (capable_wrt_inode_uidgid(idmap, inode, CAP_CHOWN))
                return true;
        if (!vfsgid_valid(vfsgid) &&
            ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
                return true;
        return false;
}

/**
 * setattr_prepare - check if attribute changes to a dentry are allowed
 * @idmap:      idmap of the mount the inode was found from
 * @dentry:     dentry to check
 * @attr:       attributes to change
 *
 * Check if we are allowed to change the attributes contained in @attr
 * in the given dentry.  This includes the normal unix access permission
 * checks, as well as checks for rlimits and others. The function also clears
 * SGID bit from mode if user is not allowed to set it. Also file capabilities
 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
 *
 * If the inode has been found through an idmapped mount the idmap of
 * the vfsmount must be passed through @idmap. This function will then
 * take care to map the inode according to @idmap before checking
 * permissions. On non-idmapped mounts or if permission checking is to be
 * performed on the raw inode simply pass @nop_mnt_idmap.
 *
 * Should be called as the first thing in ->setattr implementations,
 * possibly after taking additional locks.
 */
int setattr_prepare(struct mnt_idmap *idmap, struct dentry *dentry,
                    struct iattr *attr)
{
        struct inode *inode = d_inode(dentry);
        unsigned int ia_valid = attr->ia_valid;

        /*
         * First check size constraints.  These can't be overriden using
         * ATTR_FORCE.
         */
        if (ia_valid & ATTR_SIZE) {
                int error = inode_newsize_ok(inode, attr->ia_size);
                if (error)
                        return error;
        }

        /* If force is set do it anyway. */
        if (ia_valid & ATTR_FORCE)
                goto kill_priv;

        /* Make sure a caller can chown. */
        if ((ia_valid & ATTR_UID) &&
            !chown_ok(idmap, inode, attr->ia_vfsuid))
                return -EPERM;

        /* Make sure caller can chgrp. */
        if ((ia_valid & ATTR_GID) &&
            !chgrp_ok(idmap, inode, attr->ia_vfsgid))
                return -EPERM;

        /* Make sure a caller can chmod. */
        if (ia_valid & ATTR_MODE) {
                vfsgid_t vfsgid;

                if (!inode_owner_or_capable(idmap, inode))
                        return -EPERM;

                if (ia_valid & ATTR_GID)
                        vfsgid = attr->ia_vfsgid;
                else
                        vfsgid = i_gid_into_vfsgid(idmap, inode);

                /* Also check the setgid bit! */
                if (!in_group_or_capable(idmap, inode, vfsgid))
                        attr->ia_mode &= ~S_ISGID;
        }

        /* Check for setting the inode time. */
        if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
                if (!inode_owner_or_capable(idmap, inode))
                        return -EPERM;
        }

kill_priv:
        /* User has permission for the change */
        if (ia_valid & ATTR_KILL_PRIV) {
                int error;

                error = security_inode_killpriv(idmap, dentry);
                if (error)
                        return error;
        }

        return 0;
}
EXPORT_SYMBOL(setattr_prepare);

/**
 * inode_newsize_ok - may this inode be truncated to a given size
 * @inode:      the inode to be truncated
 * @offset:     the new size to assign to the inode
 *
 * inode_newsize_ok must be called with i_mutex held.
 *
 * inode_newsize_ok will check filesystem limits and ulimits to check that the
 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
 * when necessary. Caller must not proceed with inode size change if failure is
 * returned. @inode must be a file (not directory), with appropriate
 * permissions to allow truncate (inode_newsize_ok does NOT check these
 * conditions).
 *
 * Return: 0 on success, -ve errno on failure
 */
int inode_newsize_ok(const struct inode *inode, loff_t offset)
{
        if (offset < 0)
                return -EINVAL;
        if (inode->i_size < offset) {
                unsigned long limit;

                limit = rlimit(RLIMIT_FSIZE);
                if (limit != RLIM_INFINITY && offset > limit)
                        goto out_sig;
                if (offset > inode->i_sb->s_maxbytes)
                        goto out_big;
        } else {
                /*
                 * truncation of in-use swapfiles is disallowed - it would
                 * cause subsequent swapout to scribble on the now-freed
                 * blocks.
                 */
                if (IS_SWAPFILE(inode))
                        return -ETXTBSY;
        }

        return 0;
out_sig:
        send_sig(SIGXFSZ, current, 0);
out_big:
        return -EFBIG;
}
EXPORT_SYMBOL(inode_newsize_ok);

/**
 * setattr_copy - copy simple metadata updates into the generic inode
 * @idmap:      idmap of the mount the inode was found from
 * @inode:      the inode to be updated
 * @attr:       the new attributes
 *
 * setattr_copy must be called with i_mutex held.
 *
 * setattr_copy updates the inode's metadata with that specified
 * in attr on idmapped mounts. Necessary permission checks to determine
 * whether or not the S_ISGID property needs to be removed are performed with
 * the correct idmapped mount permission helpers.
 * Noticeably missing is inode size update, which is more complex
 * as it requires pagecache updates.
 *
 * If the inode has been found through an idmapped mount the idmap of
 * the vfsmount must be passed through @idmap. This function will then
 * take care to map the inode according to @idmap before checking
 * permissions. On non-idmapped mounts or if permission checking is to be
 * performed on the raw inode simply pass @nop_mnt_idmap.
 *
 * The inode is not marked as dirty after this operation. The rationale is
 * that for "simple" filesystems, the struct inode is the inode storage.
 * The caller is free to mark the inode dirty afterwards if needed.
 */
void setattr_copy(struct mnt_idmap *idmap, struct inode *inode,
                  const struct iattr *attr)
{
        unsigned int ia_valid = attr->ia_valid;

        i_uid_update(idmap, attr, inode);
        i_gid_update(idmap, attr, inode);
        if (ia_valid & ATTR_ATIME)
                inode_set_atime_to_ts(inode, attr->ia_atime);
        if (ia_valid & ATTR_MTIME)
                inode_set_mtime_to_ts(inode, attr->ia_mtime);
        if (ia_valid & ATTR_CTIME)
                inode_set_ctime_to_ts(inode, attr->ia_ctime);
        if (ia_valid & ATTR_MODE) {
                umode_t mode = attr->ia_mode;
                if (!in_group_or_capable(idmap, inode,
                                         i_gid_into_vfsgid(idmap, inode)))
                        mode &= ~S_ISGID;
                inode->i_mode = mode;
        }
}
EXPORT_SYMBOL(setattr_copy);

int may_setattr(struct mnt_idmap *idmap, struct inode *inode,
                unsigned int ia_valid)
{
        int error;

        if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
                if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
                        return -EPERM;
        }

        /*
         * If utimes(2) and friends are called with times == NULL (or both
         * times are UTIME_NOW), then we need to check for write permission
         */
        if (ia_valid & ATTR_TOUCH) {
                if (IS_IMMUTABLE(inode))
                        return -EPERM;

                if (!inode_owner_or_capable(idmap, inode)) {
                        error = inode_permission(idmap, inode, MAY_WRITE);
                        if (error)
                                return error;
                }
        }
        return 0;
}
EXPORT_SYMBOL(may_setattr);

/**
 * notify_change - modify attributes of a filesystem object
 * @idmap:      idmap of the mount the inode was found from
 * @dentry:     object affected
 * @attr:       new attributes
 * @delegated_inode: returns inode, if the inode is delegated
 *
 * The caller must hold the i_mutex on the affected object.
 *
 * If notify_change discovers a delegation in need of breaking,
 * it will return -EWOULDBLOCK and return a reference to the inode in
 * delegated_inode.  The caller should then break the delegation and
 * retry.  Because breaking a delegation may take a long time, the
 * caller should drop the i_mutex before doing so.
 *
 * Alternatively, a caller may pass NULL for delegated_inode.  This may
 * be appropriate for callers that expect the underlying filesystem not
 * to be NFS exported.  Also, passing NULL is fine for callers holding
 * the file open for write, as there can be no conflicting delegation in
 * that case.
 *
 * If the inode has been found through an idmapped mount the idmap of
 * the vfsmount must be passed through @idmap. This function will then
 * take care to map the inode according to @idmap before checking
 * permissions. On non-idmapped mounts or if permission checking is to be
 * performed on the raw inode simply pass @nop_mnt_idmap.
 */
int notify_change(struct mnt_idmap *idmap, struct dentry *dentry,
                  struct iattr *attr, struct inode **delegated_inode)
{
        struct inode *inode = dentry->d_inode;
        umode_t mode = inode->i_mode;
        int error;
        struct timespec64 now;
        unsigned int ia_valid = attr->ia_valid;

        WARN_ON_ONCE(!inode_is_locked(inode));

        error = may_setattr(idmap, inode, ia_valid);
        if (error)
                return error;

        if ((ia_valid & ATTR_MODE)) {
                /*
                 * Don't allow changing the mode of symlinks:
                 *
                 * (1) The vfs doesn't take the mode of symlinks into account
                 *     during permission checking.
                 * (2) This has never worked correctly. Most major filesystems
                 *     did return EOPNOTSUPP due to interactions with POSIX ACLs
                 *     but did still updated the mode of the symlink.
                 *     This inconsistency led system call wrapper providers such
                 *     as libc to block changing the mode of symlinks with
                 *     EOPNOTSUPP already.
                 * (3) To even do this in the first place one would have to use
                 *     specific file descriptors and quite some effort.
                 */
                if (S_ISLNK(inode->i_mode))
                        return -EOPNOTSUPP;

                /* Flag setting protected by i_mutex */
                if (is_sxid(attr->ia_mode))
                        inode->i_flags &= ~S_NOSEC;
        }

        now = current_time(inode);

        attr->ia_ctime = now;
        if (!(ia_valid & ATTR_ATIME_SET))
                attr->ia_atime = now;
        else
                attr->ia_atime = timestamp_truncate(attr->ia_atime, inode);
        if (!(ia_valid & ATTR_MTIME_SET))
                attr->ia_mtime = now;
        else
                attr->ia_mtime = timestamp_truncate(attr->ia_mtime, inode);

        if (ia_valid & ATTR_KILL_PRIV) {
                error = security_inode_need_killpriv(dentry);
                if (error < 0)
                        return error;
                if (error == 0)
                        ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV;
        }

        /*
         * We now pass ATTR_KILL_S*ID to the lower level setattr function so
         * that the function has the ability to reinterpret a mode change
         * that's due to these bits. This adds an implicit restriction that
         * no function will ever call notify_change with both ATTR_MODE and
         * ATTR_KILL_S*ID set.
         */
        if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
            (ia_valid & ATTR_MODE))
                BUG();

        if (ia_valid & ATTR_KILL_SUID) {
                if (mode & S_ISUID) {
                        ia_valid = attr->ia_valid |= ATTR_MODE;
                        attr->ia_mode = (inode->i_mode & ~S_ISUID);
                }
        }
        if (ia_valid & ATTR_KILL_SGID) {
                if (mode & S_ISGID) {
                        if (!(ia_valid & ATTR_MODE)) {
                                ia_valid = attr->ia_valid |= ATTR_MODE;
                                attr->ia_mode = inode->i_mode;
                        }
                        attr->ia_mode &= ~S_ISGID;
                }
        }
        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(idmap, inode->i_sb->s_user_ns,
                                  attr->ia_vfsuid))
                return -EOVERFLOW;
        if (ia_valid & ATTR_GID &&
            !vfsgid_has_fsmapping(idmap, 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(idmap, inode)))
                return -EOVERFLOW;
        if (!(ia_valid & ATTR_GID) &&
            !vfsgid_valid(i_gid_into_vfsgid(idmap, inode)))
                return -EOVERFLOW;

        error = security_inode_setattr(idmap, dentry, attr);
        if (error)
                return error;

        /*
         * If ATTR_DELEG is set, then these attributes are being set on
         * behalf of the holder of a write delegation. We want to avoid
         * breaking the delegation in this case.
         */
        if (!(ia_valid & ATTR_DELEG)) {
                error = try_break_deleg(inode, delegated_inode);
                if (error)
                        return error;
        }

        if (inode->i_op->setattr)
                error = inode->i_op->setattr(idmap, dentry, attr);
        else
                error = simple_setattr(idmap, dentry, attr);

        if (!error) {
                fsnotify_change(dentry, ia_valid);
                security_inode_post_setattr(idmap, dentry, ia_valid);
        }

        return error;
}
EXPORT_SYMBOL(notify_change);