From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- fs/attr.c | 511 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 511 insertions(+) create mode 100644 fs/attr.c (limited to 'fs/attr.c') diff --git a/fs/attr.c b/fs/attr.c new file mode 100644 index 000000000..3172f57f7 --- /dev/null +++ b/fs/attr.c @@ -0,0 +1,511 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/fs/attr.c + * + * Copyright (C) 1991, 1992 Linus Torvalds + * changes by Thomas Schoebel-Theuer + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "internal.h" + +/** + * setattr_should_drop_sgid - determine whether the setgid bit needs to be + * removed + * @mnt_userns: user namespace 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 user_namespace *mnt_userns, + 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(mnt_userns, inode, + i_gid_into_vfsgid(mnt_userns, 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 + * @mnt_userns: user namespace 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 user_namespace *mnt_userns, + 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(mnt_userns, 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 + * @mnt_userns: user namespace 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 user namespace of + * the vfsmount must be passed through @mnt_userns. This function will then + * take care to map the inode according to @mnt_userns before checking + * permissions. On non-idmapped mounts or if permission checking is to be + * performed on the raw inode simply passs init_user_ns. + */ +static bool chown_ok(struct user_namespace *mnt_userns, + const struct inode *inode, vfsuid_t ia_vfsuid) +{ + vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns, inode); + if (vfsuid_eq_kuid(vfsuid, current_fsuid()) && + vfsuid_eq(ia_vfsuid, vfsuid)) + return true; + if (capable_wrt_inode_uidgid(mnt_userns, 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 + * @mnt_userns: user namespace 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 user namespace of + * the vfsmount must be passed through @mnt_userns. This function will then + * take care to map the inode according to @mnt_userns before checking + * permissions. On non-idmapped mounts or if permission checking is to be + * performed on the raw inode simply passs init_user_ns. + */ +static bool chgrp_ok(struct user_namespace *mnt_userns, + const struct inode *inode, vfsgid_t ia_vfsgid) +{ + vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode); + vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns, 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(mnt_userns, 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 + * @mnt_userns: user namespace 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 user namespace of + * the vfsmount must be passed through @mnt_userns. This function will then + * take care to map the inode according to @mnt_userns before checking + * permissions. On non-idmapped mounts or if permission checking is to be + * performed on the raw inode simply passs init_user_ns. + * + * Should be called as the first thing in ->setattr implementations, + * possibly after taking additional locks. + */ +int setattr_prepare(struct user_namespace *mnt_userns, 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(mnt_userns, inode, attr->ia_vfsuid)) + return -EPERM; + + /* Make sure caller can chgrp. */ + if ((ia_valid & ATTR_GID) && + !chgrp_ok(mnt_userns, 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(mnt_userns, inode)) + return -EPERM; + + if (ia_valid & ATTR_GID) + vfsgid = attr->ia_vfsgid; + else + vfsgid = i_gid_into_vfsgid(mnt_userns, inode); + + /* Also check the setgid bit! */ + if (!in_group_or_capable(mnt_userns, 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(mnt_userns, inode)) + return -EPERM; + } + +kill_priv: + /* User has permission for the change */ + if (ia_valid & ATTR_KILL_PRIV) { + int error; + + error = security_inode_killpriv(mnt_userns, 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 + * @mnt_userns: user namespace 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 user namespace of + * the vfsmount must be passed through @mnt_userns. This function will then + * take care to map the inode according to @mnt_userns before checking + * permissions. On non-idmapped mounts or if permission checking is to be + * performed on the raw inode simply passs init_user_ns. + * + * 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 user_namespace *mnt_userns, struct inode *inode, + const struct iattr *attr) +{ + unsigned int ia_valid = attr->ia_valid; + + i_uid_update(mnt_userns, attr, inode); + i_gid_update(mnt_userns, attr, inode); + 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; + if (ia_valid & ATTR_MODE) { + umode_t mode = attr->ia_mode; + if (!in_group_or_capable(mnt_userns, inode, + i_gid_into_vfsgid(mnt_userns, inode))) + mode &= ~S_ISGID; + inode->i_mode = mode; + } +} +EXPORT_SYMBOL(setattr_copy); + +int may_setattr(struct user_namespace *mnt_userns, 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(mnt_userns, inode)) { + error = inode_permission(mnt_userns, inode, MAY_WRITE); + if (error) + return error; + } + } + return 0; +} +EXPORT_SYMBOL(may_setattr); + +/** + * notify_change - modify attributes of a filesytem object + * @mnt_userns: user namespace 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 user namespace of + * the vfsmount must be passed through @mnt_userns. This function will then + * take care to map the inode according to @mnt_userns before checking + * permissions. On non-idmapped mounts or if permission checking is to be + * performed on the raw inode simply passs init_user_ns. + */ +int notify_change(struct user_namespace *mnt_userns, 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(mnt_userns, 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(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); -- cgit v1.2.3