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fs/attr.c
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// SPDX-License-Identifier: GPL-2.0 |
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/* * linux/fs/attr.c * * Copyright (C) 1991, 1992 Linus Torvalds * changes by Thomas Schoebel-Theuer */ |
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#include <linux/export.h> |
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#include <linux/time.h> #include <linux/mm.h> #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/security.h> |
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#include <linux/evm.h> |
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#include <linux/ima.h> |
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|
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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; } |
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/** |
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* setattr_prepare - check if attribute changes to a dentry are allowed * @dentry: dentry to check |
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* @attr: attributes to change * * 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 * 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. |
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* * Should be called as the first thing in ->setattr implementations, * possibly after taking additional locks. */ |
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int setattr_prepare(struct dentry *dentry, 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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/* * 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; } |
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/* If force is set do it anyway. */ 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) && !chown_ok(inode, attr->ia_uid)) |
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return -EPERM; |
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/* Make sure caller can chgrp. */ |
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if ((ia_valid & ATTR_GID) && !chgrp_ok(inode, attr->ia_gid)) |
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return -EPERM; |
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/* Make sure a caller can chmod. */ if (ia_valid & ATTR_MODE) { |
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if (!inode_owner_or_capable(inode)) |
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return -EPERM; |
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/* Also check the setgid bit! */ if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : |
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inode->i_gid) && |
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!capable_wrt_inode_uidgid(inode, CAP_FSETID)) |
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attr->ia_mode &= ~S_ISGID; } /* 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(inode)) |
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return -EPERM; |
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} |
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|
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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; } |
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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 * @inode: the inode to be truncated * @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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* 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). |
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* * Return: 0 on success, -ve errno on failure |
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*/ int inode_newsize_ok(const struct inode *inode, loff_t offset) { if (inode->i_size < offset) { unsigned long limit; |
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limit = rlimit(RLIMIT_FSIZE); |
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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); |
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/** |
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* setattr_copy - copy simple metadata updates into the generic inode |
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* @inode: the inode to be updated * @attr: the new attributes * |
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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. Noticeably missing is inode size update, which is more complex |
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* as it requires pagecache updates. |
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* * 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. */ |
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void setattr_copy(struct inode *inode, const struct iattr *attr) |
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{ unsigned int ia_valid = attr->ia_valid; |
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|
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if (ia_valid & ATTR_UID) inode->i_uid = attr->ia_uid; if (ia_valid & ATTR_GID) inode->i_gid = attr->ia_gid; |
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if (ia_valid & ATTR_ATIME) inode->i_atime = attr->ia_atime; if (ia_valid & ATTR_MTIME) inode->i_mtime = attr->ia_mtime; if (ia_valid & ATTR_CTIME) inode->i_ctime = attr->ia_ctime; |
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if (ia_valid & ATTR_MODE) { umode_t mode = attr->ia_mode; |
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if (!in_group_p(inode->i_gid) && |
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!capable_wrt_inode_uidgid(inode, CAP_FSETID)) |
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mode &= ~S_ISGID; inode->i_mode = mode; } |
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} |
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EXPORT_SYMBOL(setattr_copy); |
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|
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/** * notify_change - modify attributes of a filesytem object * @dentry: object affected |
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* @attr: new attributes |
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* @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. */ |
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int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode) |
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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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if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) return -EPERM; } |
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/* * 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)) { |
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error = inode_permission(inode, MAY_WRITE); |
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if (error) 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 */ if (is_sxid(amode)) inode->i_flags &= ~S_NOSEC; } |
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now = current_time(inode); |
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attr->ia_ctime = now; if (!(ia_valid & ATTR_ATIME_SET)) attr->ia_atime = now; |
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else attr->ia_atime = timestamp_truncate(attr->ia_atime, inode); |
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if (!(ia_valid & ATTR_MTIME_SET)) attr->ia_mtime = now; |
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else 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) ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV; |
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} |
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/* * 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(); |
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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; attr->ia_mode = (inode->i_mode & ~S_ISUID); |
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} } if (ia_valid & ATTR_KILL_SGID) { |
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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; } } |
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if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID))) |
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return 0; |
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/* * 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; |
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/* 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; |
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error = security_inode_setattr(dentry, attr); if (error) return error; |
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error = try_break_deleg(inode, delegated_inode); if (error) return error; |
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|
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if (inode->i_op->setattr) |
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error = inode->i_op->setattr(dentry, attr); |
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else error = simple_setattr(dentry, attr); |
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|
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if (!error) { |
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fsnotify_change(dentry, ia_valid); |
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ima_inode_post_setattr(dentry); |
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evm_inode_post_setattr(dentry, ia_valid); } |
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return error; } |
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EXPORT_SYMBOL(notify_change); |