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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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SPDX-License-Identifier: GPL-2.0/* * /proc/sys support */#include <linux/init.h>#include <linux/sysctl.h>#include <linux/poll.h>#include <linux/proc_fs.h>#include <linux/printk.h>#include <linux/security.h>#include <linux/sched.h>#include <linux/cred.h>#include <linux/namei.h>#include <linux/mm.h>#include <linux/uio.h>#include <linux/module.h>#include <linux/bpf-cgroup.h>#include <linux/mount.h>#include <linux/kmemleak.h>#include <linux/lockdep.h>#include "internal.h"
#define list_for_each_table_entry(entry, header) \ entry = header->ctl_table; \ for (size_t i = 0 ; i < header->ctl_table_size; ++i, entry++)
static const struct dentry_operations proc_sys_dentry_operations;static const struct file_operations proc_sys_file_operations;static const struct inode_operations proc_sys_inode_operations;static const struct file_operations proc_sys_dir_file_operations;static const struct inode_operations proc_sys_dir_operations;
/* * Support for permanently empty directories. * Must be non-empty to avoid sharing an address with other tables. */static const struct ctl_table sysctl_mount_point[] = { { }};
/** * register_sysctl_mount_point() - registers a sysctl mount point * @path: path for the mount point * * Used to create a permanently empty directory to serve as mount point. * There are some subtle but important permission checks this allows in the * case of unprivileged mounts. */struct ctl_table_header *register_sysctl_mount_point(const char *path){ return register_sysctl_sz(path, sysctl_mount_point, 0);}EXPORT_SYMBOL(register_sysctl_mount_point);
#define sysctl_is_perm_empty_ctl_header(hptr) \ (hptr->type == SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)#define sysctl_set_perm_empty_ctl_header(hptr) \ (hptr->type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)#define sysctl_clear_perm_empty_ctl_header(hptr) \ (hptr->type = SYSCTL_TABLE_TYPE_DEFAULT)
void proc_sys_poll_notify(struct ctl_table_poll *poll){ if (!poll) return;
atomic_inc(&poll->event); wake_up_interruptible(&poll->wait);}
static const struct ctl_table root_table[] = { { .procname = "", .mode = S_IFDIR|S_IRUGO|S_IXUGO, },};static struct ctl_table_root sysctl_table_root = { .default_set.dir.header = { {{.count = 1, .nreg = 1, .ctl_table = root_table }}, .ctl_table_arg = root_table, .root = &sysctl_table_root, .set = &sysctl_table_root.default_set, },};
static DEFINE_SPINLOCK(sysctl_lock);
static void drop_sysctl_table(struct ctl_table_header *header);static int sysctl_follow_link(struct ctl_table_header **phead, const struct ctl_table **pentry);static int insert_links(struct ctl_table_header *head);static void put_links(struct ctl_table_header *header);
static void sysctl_print_dir(struct ctl_dir *dir){ if (dir->header.parent) sysctl_print_dir(dir->header.parent); pr_cont("%s/", dir->header.ctl_table[0].procname);}
static int namecmp(const char *name1, int len1, const char *name2, int len2){ int cmp;
cmp = memcmp(name1, name2, min(len1, len2)); if (cmp == 0) cmp = len1 - len2; return cmp;}
static const struct ctl_table *find_entry(struct ctl_table_header **phead, struct ctl_dir *dir, const char *name, int namelen){ struct ctl_table_header *head; const struct ctl_table *entry; struct rb_node *node = dir->root.rb_node;
lockdep_assert_held(&sysctl_lock);
while (node) { struct ctl_node *ctl_node; const char *procname; int cmp;
ctl_node = rb_entry(node, struct ctl_node, node); head = ctl_node->header; entry = &head->ctl_table[ctl_node - head->node]; procname = entry->procname;
cmp = namecmp(name, namelen, procname, strlen(procname)); if (cmp < 0) node = node->rb_left; else if (cmp > 0) node = node->rb_right; else { *phead = head; return entry; } } return NULL;}
static int insert_entry(struct ctl_table_header *head, const struct ctl_table *entry){ struct rb_node *node = &head->node[entry - head->ctl_table].node; struct rb_node **p = &head->parent->root.rb_node; struct rb_node *parent = NULL; const char *name = entry->procname; int namelen = strlen(name);
while (*p) { struct ctl_table_header *parent_head; const struct ctl_table *parent_entry; struct ctl_node *parent_node; const char *parent_name; int cmp;
parent = *p; parent_node = rb_entry(parent, struct ctl_node, node); parent_head = parent_node->header; parent_entry = &parent_head->ctl_table[parent_node - parent_head->node]; parent_name = parent_entry->procname;
cmp = namecmp(name, namelen, parent_name, strlen(parent_name)); if (cmp < 0) p = &(*p)->rb_left; else if (cmp > 0) p = &(*p)->rb_right; else { pr_err("sysctl duplicate entry: "); sysctl_print_dir(head->parent); pr_cont("%s\n", entry->procname); return -EEXIST; } }
rb_link_node(node, parent, p); rb_insert_color(node, &head->parent->root); return 0;}
static void erase_entry(struct ctl_table_header *head, const struct ctl_table *entry){ struct rb_node *node = &head->node[entry - head->ctl_table].node;
rb_erase(node, &head->parent->root);}
static void init_header(struct ctl_table_header *head, struct ctl_table_root *root, struct ctl_table_set *set, struct ctl_node *node, const struct ctl_table *table, size_t table_size){ head->ctl_table = table; head->ctl_table_size = table_size; head->ctl_table_arg = table; head->used = 0; head->count = 1; head->nreg = 1; head->unregistering = NULL; head->root = root; head->set = set; head->parent = NULL; head->node = node; INIT_HLIST_HEAD(&head->inodes); if (node) { const struct ctl_table *entry;
list_for_each_table_entry(entry, head) { node->header = head; node++; } } if (table == sysctl_mount_point) sysctl_set_perm_empty_ctl_header(head);}
static void erase_header(struct ctl_table_header *head){ const struct ctl_table *entry;
list_for_each_table_entry(entry, head) erase_entry(head, entry);}
static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header){ const struct ctl_table *entry; struct ctl_table_header *dir_h = &dir->header; int err;
/* Is this a permanently empty directory? */ if (sysctl_is_perm_empty_ctl_header(dir_h)) return -EROFS;
/* Am I creating a permanently empty directory? */ if (sysctl_is_perm_empty_ctl_header(header)) { if (!RB_EMPTY_ROOT(&dir->root)) return -EINVAL; sysctl_set_perm_empty_ctl_header(dir_h); }
dir_h->nreg++; header->parent = dir; err = insert_links(header); if (err) goto fail_links; list_for_each_table_entry(entry, header) { err = insert_entry(header, entry); if (err) goto fail; } return 0;fail: erase_header(header); put_links(header);fail_links: if (header->ctl_table == sysctl_mount_point) sysctl_clear_perm_empty_ctl_header(dir_h); header->parent = NULL; drop_sysctl_table(dir_h); return err;}
static int use_table(struct ctl_table_header *p){ lockdep_assert_held(&sysctl_lock);
if (unlikely(p->unregistering)) return 0; p->used++; return 1;}
static void unuse_table(struct ctl_table_header *p){ lockdep_assert_held(&sysctl_lock);
if (!--p->used) if (unlikely(p->unregistering)) complete(p->unregistering);}
static void proc_sys_invalidate_dcache(struct ctl_table_header *head){ proc_invalidate_siblings_dcache(&head->inodes, &sysctl_lock);}
static void start_unregistering(struct ctl_table_header *p){ /* will reacquire if has to wait */ lockdep_assert_held(&sysctl_lock);
/* * if p->used is 0, nobody will ever touch that entry again; * we'll eliminate all paths to it before dropping sysctl_lock */ if (unlikely(p->used)) { struct completion wait; init_completion(&wait); p->unregistering = &wait; spin_unlock(&sysctl_lock); wait_for_completion(&wait); } else { /* anything non-NULL; we'll never dereference it */ p->unregistering = ERR_PTR(-EINVAL); spin_unlock(&sysctl_lock); } /* * Invalidate dentries for unregistered sysctls: namespaced sysctls * can have duplicate names and contaminate dcache very badly. */ proc_sys_invalidate_dcache(p); /* * do not remove from the list until nobody holds it; walking the * list in do_sysctl() relies on that. */ spin_lock(&sysctl_lock); erase_header(p);}
static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head){ BUG_ON(!head); spin_lock(&sysctl_lock); if (!use_table(head)) head = ERR_PTR(-ENOENT); spin_unlock(&sysctl_lock); return head;}
static void sysctl_head_finish(struct ctl_table_header *head){ if (!head) return; spin_lock(&sysctl_lock); unuse_table(head); spin_unlock(&sysctl_lock);}
static struct ctl_table_set *lookup_header_set(struct ctl_table_root *root){ struct ctl_table_set *set = &root->default_set; if (root->lookup) set = root->lookup(root); return set;}
static const struct ctl_table *lookup_entry(struct ctl_table_header **phead, struct ctl_dir *dir, const char *name, int namelen){ struct ctl_table_header *head; const struct ctl_table *entry;
spin_lock(&sysctl_lock); entry = find_entry(&head, dir, name, namelen); if (entry && use_table(head)) *phead = head; else entry = NULL; spin_unlock(&sysctl_lock); return entry;}
static struct ctl_node *first_usable_entry(struct rb_node *node){ struct ctl_node *ctl_node;
for (;node; node = rb_next(node)) { ctl_node = rb_entry(node, struct ctl_node, node); if (use_table(ctl_node->header)) return ctl_node; } return NULL;}
static void first_entry(struct ctl_dir *dir, struct ctl_table_header **phead, const struct ctl_table **pentry){ struct ctl_table_header *head = NULL; const struct ctl_table *entry = NULL; struct ctl_node *ctl_node;
spin_lock(&sysctl_lock); ctl_node = first_usable_entry(rb_first(&dir->root)); spin_unlock(&sysctl_lock); if (ctl_node) { head = ctl_node->header; entry = &head->ctl_table[ctl_node - head->node]; } *phead = head; *pentry = entry;}
static void next_entry(struct ctl_table_header **phead, const struct ctl_table **pentry){ struct ctl_table_header *head = *phead; const struct ctl_table *entry = *pentry; struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
spin_lock(&sysctl_lock); unuse_table(head);
ctl_node = first_usable_entry(rb_next(&ctl_node->node)); spin_unlock(&sysctl_lock); head = NULL; if (ctl_node) { head = ctl_node->header; entry = &head->ctl_table[ctl_node - head->node]; } *phead = head; *pentry = entry;}
/* * sysctl_perm does NOT grant the superuser all rights automatically, because * some sysctl variables are readonly even to root. */
static int test_perm(int mode, int op){ if (uid_eq(current_euid(), GLOBAL_ROOT_UID)) mode >>= 6; else if (in_egroup_p(GLOBAL_ROOT_GID)) mode >>= 3; if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0) return 0; return -EACCES;}
static int sysctl_perm(struct ctl_table_header *head, const struct ctl_table *table, int op){ struct ctl_table_root *root = head->root; int mode;
if (root->permissions) mode = root->permissions(head, table); else mode = table->mode;
return test_perm(mode, op);}
static struct inode *proc_sys_make_inode(struct super_block *sb, struct ctl_table_header *head, const struct ctl_table *table){ struct ctl_table_root *root = head->root; struct inode *inode; struct proc_inode *ei;
inode = new_inode(sb); if (!inode) return ERR_PTR(-ENOMEM);
inode->i_ino = get_next_ino();
ei = PROC_I(inode);
spin_lock(&sysctl_lock); if (unlikely(head->unregistering)) { spin_unlock(&sysctl_lock); iput(inode); return ERR_PTR(-ENOENT); } ei->sysctl = head; ei->sysctl_entry = table; hlist_add_head_rcu(&ei->sibling_inodes, &head->inodes); head->count++; spin_unlock(&sysctl_lock);
simple_inode_init_ts(inode); inode->i_mode = table->mode; if (!S_ISDIR(table->mode)) { inode->i_mode |= S_IFREG; inode->i_op = &proc_sys_inode_operations; inode->i_fop = &proc_sys_file_operations; } else { inode->i_mode |= S_IFDIR; inode->i_op = &proc_sys_dir_operations; inode->i_fop = &proc_sys_dir_file_operations; if (sysctl_is_perm_empty_ctl_header(head)) make_empty_dir_inode(inode); }
inode->i_uid = GLOBAL_ROOT_UID; inode->i_gid = GLOBAL_ROOT_GID; if (root->set_ownership) root->set_ownership(head, &inode->i_uid, &inode->i_gid);
return inode;}
void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head){ spin_lock(&sysctl_lock); hlist_del_init_rcu(&PROC_I(inode)->sibling_inodes); if (!--head->count) kfree_rcu(head, rcu); spin_unlock(&sysctl_lock);}
static struct ctl_table_header *grab_header(struct inode *inode){ struct ctl_table_header *head = PROC_I(inode)->sysctl; if (!head) head = &sysctl_table_root.default_set.dir.header; return sysctl_head_grab(head);}
static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags){ struct ctl_table_header *head = grab_header(dir); struct ctl_table_header *h = NULL; const struct qstr *name = &dentry->d_name; const struct ctl_table *p; struct inode *inode; struct dentry *err = ERR_PTR(-ENOENT); struct ctl_dir *ctl_dir; int ret;
if (IS_ERR(head)) return ERR_CAST(head);
ctl_dir = container_of(head, struct ctl_dir, header);
p = lookup_entry(&h, ctl_dir, name->name, name->len); if (!p) goto out;
if (S_ISLNK(p->mode)) { ret = sysctl_follow_link(&h, &p); err = ERR_PTR(ret); if (ret) goto out; }
inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p); err = d_splice_alias_ops(inode, dentry, &proc_sys_dentry_operations);
out: if (h) sysctl_head_finish(h); sysctl_head_finish(head); return err;}
static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter, int write){ struct inode *inode = file_inode(iocb->ki_filp); struct ctl_table_header *head = grab_header(inode); const struct ctl_table *table = PROC_I(inode)->sysctl_entry; size_t count = iov_iter_count(iter); char *kbuf; ssize_t error;
if (IS_ERR(head)) return PTR_ERR(head);
/* * At this point we know that the sysctl was not unregistered * and won't be until we finish. */ error = -EPERM; if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ)) goto out;
/* if that can happen at all, it should be -EINVAL, not -EISDIR */ error = -EINVAL; if (!table->proc_handler) goto out;
/* don't even try if the size is too large */ error = -ENOMEM; if (count >= KMALLOC_MAX_SIZE) goto out; kbuf = kvzalloc(count + 1, GFP_KERNEL); if (!kbuf) goto out;
if (write) { error = -EFAULT; if (!copy_from_iter_full(kbuf, count, iter)) goto out_free_buf; kbuf[count] = '\0'; }
error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count, &iocb->ki_pos); if (error) goto out_free_buf;
/* careful: calling conventions are nasty here */ error = table->proc_handler(table, write, kbuf, &count, &iocb->ki_pos); if (error) goto out_free_buf;
if (!write) { error = -EFAULT; if (copy_to_iter(kbuf, count, iter) < count) goto out_free_buf; }
error = count;out_free_buf: kvfree(kbuf);out: sysctl_head_finish(head);
return error;}
static ssize_t proc_sys_read(struct kiocb *iocb, struct iov_iter *iter){ return proc_sys_call_handler(iocb, iter, 0);}
static ssize_t proc_sys_write(struct kiocb *iocb, struct iov_iter *iter){ return proc_sys_call_handler(iocb, iter, 1);}
static int proc_sys_open(struct inode *inode, struct file *filp){ struct ctl_table_header *head = grab_header(inode); const struct ctl_table *table = PROC_I(inode)->sysctl_entry;
/* sysctl was unregistered */ if (IS_ERR(head)) return PTR_ERR(head);
if (table->poll) filp->private_data = proc_sys_poll_event(table->poll);
sysctl_head_finish(head);
return 0;}
static __poll_t proc_sys_poll(struct file *filp, poll_table *wait){ struct inode *inode = file_inode(filp); struct ctl_table_header *head = grab_header(inode); const struct ctl_table *table = PROC_I(inode)->sysctl_entry; __poll_t ret = DEFAULT_POLLMASK; unsigned long event;
/* sysctl was unregistered */ if (IS_ERR(head)) return EPOLLERR | EPOLLHUP;
if (!table->proc_handler) goto out;
if (!table->poll) goto out;
event = (unsigned long)filp->private_data; poll_wait(filp, &table->poll->wait, wait);
if (event != atomic_read(&table->poll->event)) { filp->private_data = proc_sys_poll_event(table->poll); ret = EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI; }
out: sysctl_head_finish(head);
return ret;}
static bool proc_sys_fill_cache(struct file *file, struct dir_context *ctx, struct ctl_table_header *head, const struct ctl_table *table){ struct dentry *child, *dir = file->f_path.dentry; struct inode *inode; struct qstr qname; ino_t ino = 0; unsigned type = DT_UNKNOWN;
qname.name = table->procname; qname.len = strlen(table->procname); qname.hash = full_name_hash(dir, qname.name, qname.len);
child = d_lookup(dir, &qname); if (!child) { child = d_alloc_parallel(dir, &qname); if (IS_ERR(child)) return false; if (d_in_lookup(child)) { struct dentry *res; inode = proc_sys_make_inode(dir->d_sb, head, table); res = d_splice_alias_ops(inode, child, &proc_sys_dentry_operations); d_lookup_done(child); if (unlikely(res)) { dput(child);
if (IS_ERR(res)) return false;
child = res; } } } inode = d_inode(child); ino = inode->i_ino; type = inode->i_mode >> 12; dput(child); return dir_emit(ctx, qname.name, qname.len, ino, type);}
static bool proc_sys_link_fill_cache(struct file *file, struct dir_context *ctx, struct ctl_table_header *head, const struct ctl_table *table){ bool ret = true;
head = sysctl_head_grab(head); if (IS_ERR(head)) return false;
/* It is not an error if we can not follow the link ignore it */ if (sysctl_follow_link(&head, &table)) goto out;
ret = proc_sys_fill_cache(file, ctx, head, table);out: sysctl_head_finish(head); return ret;}
static int scan(struct ctl_table_header *head, const struct ctl_table *table, unsigned long *pos, struct file *file, struct dir_context *ctx){ bool res;
if ((*pos)++ < ctx->pos) return true;
if (unlikely(S_ISLNK(table->mode))) res = proc_sys_link_fill_cache(file, ctx, head, table); else res = proc_sys_fill_cache(file, ctx, head, table);
if (res) ctx->pos = *pos;
return res;}
static int proc_sys_readdir(struct file *file, struct dir_context *ctx){ struct ctl_table_header *head = grab_header(file_inode(file)); struct ctl_table_header *h = NULL; const struct ctl_table *entry; struct ctl_dir *ctl_dir; unsigned long pos;
if (IS_ERR(head)) return PTR_ERR(head);
ctl_dir = container_of(head, struct ctl_dir, header);
if (!dir_emit_dots(file, ctx)) goto out;
pos = 2;
for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) { if (!scan(h, entry, &pos, file, ctx)) { sysctl_head_finish(h); break; } }out: sysctl_head_finish(head); return 0;}
static int proc_sys_permission(struct mnt_idmap *idmap, struct inode *inode, int mask){ /* * sysctl entries that are not writeable, * are _NOT_ writeable, capabilities or not. */ struct ctl_table_header *head; const struct ctl_table *table; int error;
/* Executable files are not allowed under /proc/sys/ */ if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode)) return -EACCES;
head = grab_header(inode); if (IS_ERR(head)) return PTR_ERR(head);
table = PROC_I(inode)->sysctl_entry; if (!table) /* global root - r-xr-xr-x */ error = mask & MAY_WRITE ? -EACCES : 0; else /* Use the permissions on the sysctl table entry */ error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
sysctl_head_finish(head); return error;}
static int proc_sys_setattr(struct mnt_idmap *idmap, struct dentry *dentry, struct iattr *attr){ struct inode *inode = d_inode(dentry); int error;
if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) return -EPERM;
error = setattr_prepare(&nop_mnt_idmap, dentry, attr); if (error) return error;
setattr_copy(&nop_mnt_idmap, inode, attr); return 0;}
static int proc_sys_getattr(struct mnt_idmap *idmap, const struct path *path, struct kstat *stat, u32 request_mask, unsigned int query_flags){ struct inode *inode = d_inode(path->dentry); struct ctl_table_header *head = grab_header(inode); const struct ctl_table *table = PROC_I(inode)->sysctl_entry;
if (IS_ERR(head)) return PTR_ERR(head);
generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat); if (table) stat->mode = (stat->mode & S_IFMT) | table->mode;
sysctl_head_finish(head); return 0;}
static const struct file_operations proc_sys_file_operations = { .open = proc_sys_open, .poll = proc_sys_poll, .read_iter = proc_sys_read, .write_iter = proc_sys_write, .splice_read = copy_splice_read, .splice_write = iter_file_splice_write, .llseek = default_llseek,};
static const struct file_operations proc_sys_dir_file_operations = { .read = generic_read_dir, .iterate_shared = proc_sys_readdir, .llseek = generic_file_llseek,};
static const struct inode_operations proc_sys_inode_operations = { .permission = proc_sys_permission, .setattr = proc_sys_setattr, .getattr = proc_sys_getattr,};
static const struct inode_operations proc_sys_dir_operations = { .lookup = proc_sys_lookup, .permission = proc_sys_permission, .setattr = proc_sys_setattr, .getattr = proc_sys_getattr,};
static int proc_sys_revalidate(struct inode *dir, const struct qstr *name, struct dentry *dentry, unsigned int flags){ if (flags & LOOKUP_RCU) return -ECHILD; return !PROC_I(d_inode(dentry))->sysctl->unregistering;}
static int proc_sys_delete(const struct dentry *dentry){ return !!PROC_I(d_inode(dentry))->sysctl->unregistering;}
static int sysctl_is_seen(struct ctl_table_header *p){ struct ctl_table_set *set = p->set; int res; spin_lock(&sysctl_lock); if (p->unregistering) res = 0; else if (!set->is_seen) res = 1; else res = set->is_seen(set); spin_unlock(&sysctl_lock); return res;}
static int proc_sys_compare(const struct dentry *dentry, unsigned int len, const char *str, const struct qstr *name){ struct ctl_table_header *head; struct inode *inode;
if (name->len != len) return 1; if (memcmp(name->name, str, len)) return 1;
// false positive is fine here - we'll recheck anyway if (d_in_lookup(dentry)) return 0;
inode = d_inode_rcu(dentry); // we just might have run into dentry in the middle of __dentry_kill() if (!inode) return 1;
head = READ_ONCE(PROC_I(inode)->sysctl); return !head || !sysctl_is_seen(head);}
static const struct dentry_operations proc_sys_dentry_operations = { .d_revalidate = proc_sys_revalidate, .d_delete = proc_sys_delete, .d_compare = proc_sys_compare,};
static struct ctl_dir *find_subdir(struct ctl_dir *dir, const char *name, int namelen){ struct ctl_table_header *head; const struct ctl_table *entry;
entry = find_entry(&head, dir, name, namelen); if (!entry) return ERR_PTR(-ENOENT); if (!S_ISDIR(entry->mode)) return ERR_PTR(-ENOTDIR); return container_of(head, struct ctl_dir, header);}
static struct ctl_dir *new_dir(struct ctl_table_set *set, const char *name, int namelen){ struct ctl_table *table; struct ctl_dir *new; struct ctl_node *node; char *new_name;
new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) + sizeof(struct ctl_table) + namelen + 1, GFP_KERNEL); if (!new) return NULL;
node = (struct ctl_node *)(new + 1); table = (struct ctl_table *)(node + 1); new_name = (char *)(table + 1); memcpy(new_name, name, namelen); table[0].procname = new_name; table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO; init_header(&new->header, set->dir.header.root, set, node, table, 1);
return new;}
/** * get_subdir - find or create a subdir with the specified name. * @dir: Directory to create the subdirectory in * @name: The name of the subdirectory to find or create * @namelen: The length of name * * Takes a directory with an elevated reference count so we know that * if we drop the lock the directory will not go away. Upon success * the reference is moved from @dir to the returned subdirectory. * Upon error an error code is returned and the reference on @dir is * simply dropped. */static struct ctl_dir *get_subdir(struct ctl_dir *dir, const char *name, int namelen){ struct ctl_table_set *set = dir->header.set; struct ctl_dir *subdir, *new = NULL; int err;
spin_lock(&sysctl_lock); subdir = find_subdir(dir, name, namelen); if (!IS_ERR(subdir)) goto found; if (PTR_ERR(subdir) != -ENOENT) goto failed;
spin_unlock(&sysctl_lock); new = new_dir(set, name, namelen); spin_lock(&sysctl_lock); subdir = ERR_PTR(-ENOMEM); if (!new) goto failed;
/* Was the subdir added while we dropped the lock? */ subdir = find_subdir(dir, name, namelen); if (!IS_ERR(subdir)) goto found; if (PTR_ERR(subdir) != -ENOENT) goto failed;
/* Nope. Use the our freshly made directory entry. */ err = insert_header(dir, &new->header); subdir = ERR_PTR(err); if (err) goto failed; subdir = new;found: subdir->header.nreg++;failed: if (IS_ERR(subdir)) { pr_err("sysctl could not get directory: "); sysctl_print_dir(dir); pr_cont("%*.*s %ld\n", namelen, namelen, name, PTR_ERR(subdir)); } drop_sysctl_table(&dir->header); if (new) drop_sysctl_table(&new->header); spin_unlock(&sysctl_lock); return subdir;}
static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir){ struct ctl_dir *parent; const char *procname; if (!dir->header.parent) return &set->dir; parent = xlate_dir(set, dir->header.parent); if (IS_ERR(parent)) return parent; procname = dir->header.ctl_table[0].procname; return find_subdir(parent, procname, strlen(procname));}
static int sysctl_follow_link(struct ctl_table_header **phead, const struct ctl_table **pentry){ struct ctl_table_header *head; const struct ctl_table *entry; struct ctl_table_root *root; struct ctl_table_set *set; struct ctl_dir *dir; int ret;
spin_lock(&sysctl_lock); root = (*pentry)->data; set = lookup_header_set(root); dir = xlate_dir(set, (*phead)->parent); if (IS_ERR(dir)) ret = PTR_ERR(dir); else { const char *procname = (*pentry)->procname; head = NULL; entry = find_entry(&head, dir, procname, strlen(procname)); ret = -ENOENT; if (entry && use_table(head)) { unuse_table(*phead); *phead = head; *pentry = entry; ret = 0; } }
spin_unlock(&sysctl_lock); return ret;}
static int sysctl_err(const char *path, const struct ctl_table *table, char *fmt, ...){ struct va_format vaf; va_list args;
va_start(args, fmt); vaf.fmt = fmt; vaf.va = &args;
pr_err("sysctl table check failed: %s/%s %pV\n", path, table->procname, &vaf);
va_end(args); return -EINVAL;}
static int sysctl_check_table_array(const char *path, const struct ctl_table *table){ unsigned int extra; int err = 0;
if ((table->proc_handler == proc_douintvec) || (table->proc_handler == proc_douintvec_minmax)) { if (table->maxlen != sizeof(unsigned int)) err |= sysctl_err(path, table, "array not allowed"); }
if (table->proc_handler == proc_dou8vec_minmax) { if (table->maxlen != sizeof(u8)) err |= sysctl_err(path, table, "array not allowed");
if (table->extra1) { extra = *(unsigned int *) table->extra1; if (extra > 255U) err |= sysctl_err(path, table, "range value too large for proc_dou8vec_minmax"); } if (table->extra2) { extra = *(unsigned int *) table->extra2; if (extra > 255U) err |= sysctl_err(path, table, "range value too large for proc_dou8vec_minmax"); } }
if (table->proc_handler == proc_dobool) { if (table->maxlen != sizeof(bool)) err |= sysctl_err(path, table, "array not allowed"); }
return err;}
static int sysctl_check_table(const char *path, struct ctl_table_header *header){ const struct ctl_table *entry; int err = 0; list_for_each_table_entry(entry, header) { if (!entry->procname) err |= sysctl_err(path, entry, "procname is null"); if ((entry->proc_handler == proc_dostring) || (entry->proc_handler == proc_dobool) || (entry->proc_handler == proc_dointvec) || (entry->proc_handler == proc_douintvec) || (entry->proc_handler == proc_douintvec_minmax) || (entry->proc_handler == proc_dointvec_minmax) || (entry->proc_handler == proc_dou8vec_minmax) || (entry->proc_handler == proc_dointvec_jiffies) || (entry->proc_handler == proc_dointvec_userhz_jiffies) || (entry->proc_handler == proc_dointvec_ms_jiffies) || (entry->proc_handler == proc_doulongvec_minmax) || (entry->proc_handler == proc_doulongvec_ms_jiffies_minmax)) { if (!entry->data) err |= sysctl_err(path, entry, "No data"); if (!entry->maxlen) err |= sysctl_err(path, entry, "No maxlen"); else err |= sysctl_check_table_array(path, entry); } if (!entry->proc_handler) err |= sysctl_err(path, entry, "No proc_handler");
if ((entry->mode & (S_IRUGO|S_IWUGO)) != entry->mode) err |= sysctl_err(path, entry, "bogus .mode 0%o", entry->mode); } return err;}
static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table_header *head){ struct ctl_table *link_table, *link; struct ctl_table_header *links; const struct ctl_table *entry; struct ctl_node *node; char *link_name; int name_bytes;
name_bytes = 0; list_for_each_table_entry(entry, head) { name_bytes += strlen(entry->procname) + 1; }
links = kzalloc(sizeof(struct ctl_table_header) + sizeof(struct ctl_node)*head->ctl_table_size + sizeof(struct ctl_table)*head->ctl_table_size + name_bytes, GFP_KERNEL);
if (!links) return NULL;
node = (struct ctl_node *)(links + 1); link_table = (struct ctl_table *)(node + head->ctl_table_size); link_name = (char *)(link_table + head->ctl_table_size); link = link_table;
list_for_each_table_entry(entry, head) { int len = strlen(entry->procname) + 1; memcpy(link_name, entry->procname, len); link->procname = link_name; link->mode = S_IFLNK|S_IRWXUGO; link->data = head->root; link_name += len; link++; } init_header(links, dir->header.root, dir->header.set, node, link_table, head->ctl_table_size); links->nreg = head->ctl_table_size;
return links;}
static bool get_links(struct ctl_dir *dir, struct ctl_table_header *header, struct ctl_table_root *link_root){ struct ctl_table_header *tmp_head; const struct ctl_table *entry, *link;
if (header->ctl_table_size == 0 || sysctl_is_perm_empty_ctl_header(header)) return true;
/* Are there links available for every entry in table? */ list_for_each_table_entry(entry, header) { const char *procname = entry->procname; link = find_entry(&tmp_head, dir, procname, strlen(procname)); if (!link) return false; if (S_ISDIR(link->mode) && S_ISDIR(entry->mode)) continue; if (S_ISLNK(link->mode) && (link->data == link_root)) continue; return false; }
/* The checks passed. Increase the registration count on the links */ list_for_each_table_entry(entry, header) { const char *procname = entry->procname; link = find_entry(&tmp_head, dir, procname, strlen(procname)); tmp_head->nreg++; } return true;}
static int insert_links(struct ctl_table_header *head){ struct ctl_table_set *root_set = &sysctl_table_root.default_set; struct ctl_dir *core_parent; struct ctl_table_header *links; int err;
if (head->set == root_set) return 0;
core_parent = xlate_dir(root_set, head->parent); if (IS_ERR(core_parent)) return 0;
if (get_links(core_parent, head, head->root)) return 0;
core_parent->header.nreg++; spin_unlock(&sysctl_lock);
links = new_links(core_parent, head);
spin_lock(&sysctl_lock); err = -ENOMEM; if (!links) goto out;
err = 0; if (get_links(core_parent, head, head->root)) { kfree(links); goto out; }
err = insert_header(core_parent, links); if (err) kfree(links);out: drop_sysctl_table(&core_parent->header); return err;}
/* Find the directory for the ctl_table. If one is not found create it. */static struct ctl_dir *sysctl_mkdir_p(struct ctl_dir *dir, const char *path){ const char *name, *nextname;
for (name = path; name; name = nextname) { int namelen; nextname = strchr(name, '/'); if (nextname) { namelen = nextname - name; nextname++; } else { namelen = strlen(name); } if (namelen == 0) continue;
/* * namelen ensures if name is "foo/bar/yay" only foo is * registered first. We traverse as if using mkdir -p and * return a ctl_dir for the last directory entry. */ dir = get_subdir(dir, name, namelen); if (IS_ERR(dir)) break; } return dir;}
/** * __register_sysctl_table - register a leaf sysctl table * @set: Sysctl tree to register on * @path: The path to the directory the sysctl table is in. * * @table: the top-level table structure. This table should not be free'd * after registration. So it should not be used on stack. It can either * be a global or dynamically allocated by the caller and free'd later * after sysctl unregistration. * @table_size : The number of elements in table * * Register a sysctl table hierarchy. @table should be a filled in ctl_table * array. * * The members of the &struct ctl_table structure are used as follows: * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not * enter a sysctl file * data - a pointer to data for use by proc_handler * maxlen - the maximum size in bytes of the data * mode - the file permissions for the /proc/sys file * type - Defines the target type (described in struct definition) * proc_handler - the text handler routine (described below) * * extra1, extra2 - extra pointers usable by the proc handler routines * XXX: we should eventually modify these to use long min / max [0] * [0] https://lkml.kernel.org/87zgpte9o4.fsf@email.froward.int.ebiederm.org * * Leaf nodes in the sysctl tree will be represented by a single file * under /proc; non-leaf nodes are not allowed. * * There must be a proc_handler routine for any terminal nodes. * Several default handlers are available to cover common cases - * * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(), * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(), * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax() * * It is the handler's job to read the input buffer from user memory * and process it. The handler should return 0 on success. * * This routine returns %NULL on a failure to register, and a pointer * to the table header on success. */struct ctl_table_header *__register_sysctl_table( struct ctl_table_set *set, const char *path, const struct ctl_table *table, size_t table_size){ struct ctl_table_root *root = set->dir.header.root; struct ctl_table_header *header; struct ctl_dir *dir; struct ctl_node *node;
header = kzalloc(sizeof(struct ctl_table_header) + sizeof(struct ctl_node)*table_size, GFP_KERNEL_ACCOUNT); if (!header) return NULL;
node = (struct ctl_node *)(header + 1); init_header(header, root, set, node, table, table_size); if (sysctl_check_table(path, header)) goto fail;
spin_lock(&sysctl_lock); dir = &set->dir; /* Reference moved down the directory tree get_subdir */ dir->header.nreg++; spin_unlock(&sysctl_lock);
dir = sysctl_mkdir_p(dir, path); if (IS_ERR(dir)) goto fail; spin_lock(&sysctl_lock); if (insert_header(dir, header)) goto fail_put_dir_locked;
drop_sysctl_table(&dir->header); spin_unlock(&sysctl_lock);
return header;
fail_put_dir_locked: drop_sysctl_table(&dir->header); spin_unlock(&sysctl_lock);fail: kfree(header); return NULL;}
/** * register_sysctl_sz - register a sysctl table * @path: The path to the directory the sysctl table is in. If the path * doesn't exist we will create it for you. * @table: the table structure. The calller must ensure the life of the @table * will be kept during the lifetime use of the syctl. It must not be freed * until unregister_sysctl_table() is called with the given returned table * with this registration. If your code is non modular then you don't need * to call unregister_sysctl_table() and can instead use something like * register_sysctl_init() which does not care for the result of the syctl * registration. * @table_size: The number of elements in table. * * Register a sysctl table. @table should be a filled in ctl_table * array. A completely 0 filled entry terminates the table. * * See __register_sysctl_table for more details. */struct ctl_table_header *register_sysctl_sz(const char *path, const struct ctl_table *table, size_t table_size){ return __register_sysctl_table(&sysctl_table_root.default_set, path, table, table_size);}EXPORT_SYMBOL(register_sysctl_sz);
/** * __register_sysctl_init() - register sysctl table to path * @path: path name for sysctl base. If that path doesn't exist we will create * it for you. * @table: This is the sysctl table that needs to be registered to the path. * The caller must ensure the life of the @table will be kept during the * lifetime use of the sysctl. * @table_name: The name of sysctl table, only used for log printing when * registration fails * @table_size: The number of elements in table * * The sysctl interface is used by userspace to query or modify at runtime * a predefined value set on a variable. These variables however have default * values pre-set. Code which depends on these variables will always work even * if register_sysctl() fails. If register_sysctl() fails you'd just loose the * ability to query or modify the sysctls dynamically at run time. Chances of * register_sysctl() failing on init are extremely low, and so for both reasons * this function does not return any error as it is used by initialization code. * * Context: if your base directory does not exist it will be created for you. */void __init __register_sysctl_init(const char *path, const struct ctl_table *table, const char *table_name, size_t table_size){ struct ctl_table_header *hdr = register_sysctl_sz(path, table, table_size);
if (unlikely(!hdr)) { pr_err("failed when register_sysctl_sz %s to %s\n", table_name, path); return; } kmemleak_not_leak(hdr);}
static void put_links(struct ctl_table_header *header){ struct ctl_table_set *root_set = &sysctl_table_root.default_set; struct ctl_table_root *root = header->root; struct ctl_dir *parent = header->parent; struct ctl_dir *core_parent; const struct ctl_table *entry;
if (header->set == root_set) return;
core_parent = xlate_dir(root_set, parent); if (IS_ERR(core_parent)) return;
list_for_each_table_entry(entry, header) { struct ctl_table_header *link_head; const struct ctl_table *link; const char *name = entry->procname;
link = find_entry(&link_head, core_parent, name, strlen(name)); if (link && ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) || (S_ISLNK(link->mode) && (link->data == root)))) { drop_sysctl_table(link_head); } else { pr_err("sysctl link missing during unregister: "); sysctl_print_dir(parent); pr_cont("%s\n", name); } }}
static void drop_sysctl_table(struct ctl_table_header *header){ struct ctl_dir *parent = header->parent;
if (--header->nreg) return;
if (parent) { put_links(header); start_unregistering(header); }
if (!--header->count) kfree_rcu(header, rcu);
if (parent) drop_sysctl_table(&parent->header);}
/** * unregister_sysctl_table - unregister a sysctl table hierarchy * @header: the header returned from register_sysctl or __register_sysctl_table * * Unregisters the sysctl table and all children. proc entries may not * actually be removed until they are no longer used by anyone. */void unregister_sysctl_table(struct ctl_table_header * header){ might_sleep();
if (header == NULL) return;
spin_lock(&sysctl_lock); drop_sysctl_table(header); spin_unlock(&sysctl_lock);}EXPORT_SYMBOL(unregister_sysctl_table);
void setup_sysctl_set(struct ctl_table_set *set, struct ctl_table_root *root, int (*is_seen)(struct ctl_table_set *)){ memset(set, 0, sizeof(*set)); set->is_seen = is_seen; init_header(&set->dir.header, root, set, NULL, root_table, 1);}
void retire_sysctl_set(struct ctl_table_set *set){ WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));}
int __init proc_sys_init(void){ struct proc_dir_entry *proc_sys_root;
proc_sys_root = proc_mkdir("sys", NULL); proc_sys_root->proc_iops = &proc_sys_dir_operations; proc_sys_root->proc_dir_ops = &proc_sys_dir_file_operations; proc_sys_root->nlink = 0;
return sysctl_init_bases();}
struct sysctl_alias { const char *kernel_param; const char *sysctl_param;};
/* * Historically some settings had both sysctl and a command line parameter. * With the generic sysctl. parameter support, we can handle them at a single * place and only keep the historical name for compatibility. This is not meant * to add brand new aliases. When adding existing aliases, consider whether * the possibly different moment of changing the value (e.g. from early_param * to the moment do_sysctl_args() is called) is an issue for the specific * parameter. */static const struct sysctl_alias sysctl_aliases[] = { {"hardlockup_all_cpu_backtrace", "kernel.hardlockup_all_cpu_backtrace" }, {"hung_task_panic", "kernel.hung_task_panic" }, {"numa_zonelist_order", "vm.numa_zonelist_order" }, {"softlockup_all_cpu_backtrace", "kernel.softlockup_all_cpu_backtrace" }, { }};
static const char *sysctl_find_alias(char *param){ const struct sysctl_alias *alias;
for (alias = &sysctl_aliases[0]; alias->kernel_param != NULL; alias++) { if (strcmp(alias->kernel_param, param) == 0) return alias->sysctl_param; }
return NULL;}
bool sysctl_is_alias(char *param){ const char *alias = sysctl_find_alias(param);
return alias != NULL;}
/* Set sysctl value passed on kernel command line. */static int process_sysctl_arg(char *param, char *val, const char *unused, void *arg){ char *path; struct vfsmount **proc_mnt = arg; struct file_system_type *proc_fs_type; struct file *file; int len; int err; loff_t pos = 0; ssize_t wret;
if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) { param += sizeof("sysctl") - 1;
if (param[0] != '/' && param[0] != '.') return 0;
param++; } else { param = (char *) sysctl_find_alias(param); if (!param) return 0; }
if (!val) return -EINVAL; len = strlen(val); if (len == 0) return -EINVAL;
/* * To set sysctl options, we use a temporary mount of proc, look up the * respective sys/ file and write to it. To avoid mounting it when no * options were given, we mount it only when the first sysctl option is * found. Why not a persistent mount? There are problems with a * persistent mount of proc in that it forces userspace not to use any * proc mount options. */ if (!*proc_mnt) { proc_fs_type = get_fs_type("proc"); if (!proc_fs_type) { pr_err("Failed to find procfs to set sysctl from command line\n"); return 0; } *proc_mnt = kern_mount(proc_fs_type); put_filesystem(proc_fs_type); if (IS_ERR(*proc_mnt)) { pr_err("Failed to mount procfs to set sysctl from command line\n"); return 0; } }
path = kasprintf(GFP_KERNEL, "sys/%s", param); if (!path) panic("%s: Failed to allocate path for %s\n", __func__, param); strreplace(path, '.', '/');
file = file_open_root_mnt(*proc_mnt, path, O_WRONLY, 0); if (IS_ERR(file)) { err = PTR_ERR(file); if (err == -ENOENT) pr_err("Failed to set sysctl parameter '%s=%s': parameter not found\n", param, val); else if (err == -EACCES) pr_err("Failed to set sysctl parameter '%s=%s': permission denied (read-only?)\n", param, val); else pr_err("Error %pe opening proc file to set sysctl parameter '%s=%s'\n", file, param, val); goto out; } wret = kernel_write(file, val, len, &pos); if (wret < 0) { err = wret; if (err == -EINVAL) pr_err("Failed to set sysctl parameter '%s=%s': invalid value\n", param, val); else pr_err("Error %pe writing to proc file to set sysctl parameter '%s=%s'\n", ERR_PTR(err), param, val); } else if (wret != len) { pr_err("Wrote only %zd bytes of %d writing to proc file %s to set sysctl parameter '%s=%s\n", wret, len, path, param, val); }
err = filp_close(file, NULL); if (err) pr_err("Error %pe closing proc file to set sysctl parameter '%s=%s\n", ERR_PTR(err), param, val);out: kfree(path); return 0;}
void do_sysctl_args(void){ char *command_line; struct vfsmount *proc_mnt = NULL;
command_line = kstrdup(saved_command_line, GFP_KERNEL); if (!command_line) panic("%s: Failed to allocate copy of command line\n", __func__);
parse_args("Setting sysctl args", command_line, NULL, 0, -1, -1, &proc_mnt, process_sysctl_arg);
if (proc_mnt) kern_unmount(proc_mnt);
kfree(command_line);}