| // 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/security.h> |
| #include <linux/evm.h> |
| #include <linux/ima.h> |
| |
| static bool chown_ok(const struct inode *inode, kuid_t uid) |
| { |
| if (uid_eq(current_fsuid(), inode->i_uid) && |
| uid_eq(uid, inode->i_uid)) |
| return true; |
| if (capable_wrt_inode_uidgid(inode, CAP_CHOWN)) |
| return true; |
| if (uid_eq(inode->i_uid, INVALID_UID) && |
| ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN)) |
| return true; |
| return false; |
| } |
| |
| static bool chgrp_ok(const struct inode *inode, kgid_t gid) |
| { |
| if (uid_eq(current_fsuid(), inode->i_uid) && |
| (in_group_p(gid) || gid_eq(gid, inode->i_gid))) |
| return true; |
| if (capable_wrt_inode_uidgid(inode, CAP_CHOWN)) |
| return true; |
| if (gid_eq(inode->i_gid, INVALID_GID) && |
| 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 |
| * @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. |
| * |
| * Should be called as the first thing in ->setattr implementations, |
| * possibly after taking additional locks. |
| */ |
| int setattr_prepare(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(inode, attr->ia_uid)) |
| return -EPERM; |
| |
| /* Make sure caller can chgrp. */ |
| if ((ia_valid & ATTR_GID) && !chgrp_ok(inode, attr->ia_gid)) |
| return -EPERM; |
| |
| /* Make sure a caller can chmod. */ |
| if (ia_valid & ATTR_MODE) { |
| if (!inode_owner_or_capable(inode)) |
| return -EPERM; |
| /* Also check the setgid bit! */ |
| if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : |
| inode->i_gid) && |
| !capable_wrt_inode_uidgid(inode, CAP_FSETID)) |
| 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(inode)) |
| return -EPERM; |
| } |
| |
| kill_priv: |
| /* User has permission for the change */ |
| if (ia_valid & ATTR_KILL_PRIV) { |
| int error; |
| |
| error = security_inode_killpriv(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 (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 |
| * @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. Noticeably missing is inode size update, which is more complex |
| * as it requires pagecache updates. |
| * |
| * 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 inode *inode, const struct iattr *attr) |
| { |
| unsigned int ia_valid = attr->ia_valid; |
| |
| if (ia_valid & ATTR_UID) |
| inode->i_uid = attr->ia_uid; |
| if (ia_valid & ATTR_GID) |
| inode->i_gid = attr->ia_gid; |
| if (ia_valid & ATTR_ATIME) |
| inode->i_atime = timespec64_trunc(attr->ia_atime, |
| inode->i_sb->s_time_gran); |
| if (ia_valid & ATTR_MTIME) |
| inode->i_mtime = timespec64_trunc(attr->ia_mtime, |
| inode->i_sb->s_time_gran); |
| if (ia_valid & ATTR_CTIME) |
| inode->i_ctime = timespec64_trunc(attr->ia_ctime, |
| inode->i_sb->s_time_gran); |
| if (ia_valid & ATTR_MODE) { |
| umode_t mode = attr->ia_mode; |
| |
| if (!in_group_p(inode->i_gid) && |
| !capable_wrt_inode_uidgid(inode, CAP_FSETID)) |
| mode &= ~S_ISGID; |
| inode->i_mode = mode; |
| } |
| } |
| EXPORT_SYMBOL(setattr_copy); |
| |
| /** |
| * notify_change - modify attributes of a filesytem object |
| * @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. |
| */ |
| int notify_change(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)); |
| |
| 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(inode)) { |
| error = inode_permission(inode, MAY_WRITE); |
| if (error) |
| return error; |
| } |
| } |
| |
| if ((ia_valid & ATTR_MODE)) { |
| umode_t amode = attr->ia_mode; |
| /* Flag setting protected by i_mutex */ |
| if (is_sxid(amode)) |
| inode->i_flags &= ~S_NOSEC; |
| } |
| |
| now = current_time(inode); |
| |
| attr->ia_ctime = now; |
| if (!(ia_valid & ATTR_ATIME_SET)) |
| attr->ia_atime = now; |
| if (!(ia_valid & ATTR_MTIME_SET)) |
| attr->ia_mtime = now; |
| 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 | S_IXGRP)) == (S_ISGID | S_IXGRP)) { |
| 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 && |
| !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid)) |
| return -EOVERFLOW; |
| if (ia_valid & ATTR_GID && |
| !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid)) |
| 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) && !uid_valid(inode->i_uid)) |
| return -EOVERFLOW; |
| if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid)) |
| return -EOVERFLOW; |
| |
| error = security_inode_setattr(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(dentry, attr); |
| else |
| error = simple_setattr(dentry, attr); |
| |
| if (!error) { |
| fsnotify_change(dentry, ia_valid); |
| ima_inode_post_setattr(dentry); |
| evm_inode_post_setattr(dentry, ia_valid); |
| } |
| |
| return error; |
| } |
| EXPORT_SYMBOL(notify_change); |