diff options
Diffstat (limited to 'kernel/fs/attr.c')
| -rw-r--r-- | kernel/fs/attr.c | 278 |
1 files changed, 278 insertions, 0 deletions
diff --git a/kernel/fs/attr.c b/kernel/fs/attr.c new file mode 100644 index 000000000..6530ced19 --- /dev/null +++ b/kernel/fs/attr.c @@ -0,0 +1,278 @@ +/* + * 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/capability.h> +#include <linux/fsnotify.h> +#include <linux/fcntl.h> +#include <linux/security.h> +#include <linux/evm.h> +#include <linux/ima.h> + +/** + * inode_change_ok - check if attribute changes to an inode are allowed + * @inode: inode to check + * @attr: attributes to change + * + * Check if we are allowed to change the attributes contained in @attr + * in the given inode. This includes the normal unix access permission + * checks, as well as checks for rlimits and others. + * + * Should be called as the first thing in ->setattr implementations, + * possibly after taking additional locks. + */ +int inode_change_ok(const struct inode *inode, struct iattr *attr) +{ + 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) + return 0; + + /* Make sure a caller can chown. */ + if ((ia_valid & ATTR_UID) && + (!uid_eq(current_fsuid(), inode->i_uid) || + !uid_eq(attr->ia_uid, inode->i_uid)) && + !capable_wrt_inode_uidgid(inode, CAP_CHOWN)) + return -EPERM; + + /* Make sure caller can chgrp. */ + if ((ia_valid & ATTR_GID) && + (!uid_eq(current_fsuid(), inode->i_uid) || + (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) && + !capable_wrt_inode_uidgid(inode, CAP_CHOWN)) + 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; + } + + return 0; +} +EXPORT_SYMBOL(inode_change_ok); + +/** + * 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 + * @Returns: 0 on success, -ve errno on failure + * + * 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). + */ +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 = timespec_trunc(attr->ia_atime, + inode->i_sb->s_time_gran); + if (ia_valid & ATTR_MTIME) + inode->i_mtime = timespec_trunc(attr->ia_mtime, + inode->i_sb->s_time_gran); + if (ia_valid & ATTR_CTIME) + inode->i_ctime = timespec_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 + * @iattr: 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 timespec now; + unsigned int ia_valid = attr->ia_valid; + + WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex)); + + if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { + if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) + return -EPERM; + } + + 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_fs_time(inode->i_sb); + + 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) { + attr->ia_valid &= ~ATTR_KILL_PRIV; + ia_valid &= ~ATTR_KILL_PRIV; + error = security_inode_need_killpriv(dentry); + if (error > 0) + error = security_inode_killpriv(dentry); + if (error) + return error; + } + + /* + * 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; + + 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); |