diff options
Diffstat (limited to 'kernel/sysctl.c')
-rw-r--r-- | kernel/sysctl.c | 141 |
1 files changed, 110 insertions, 31 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 8e56e249554..9990e10192e 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -169,7 +169,7 @@ struct file_operations proc_sys_file_operations = { extern struct proc_dir_entry *proc_sys_root; -static void register_proc_table(ctl_table *, struct proc_dir_entry *); +static void register_proc_table(ctl_table *, struct proc_dir_entry *, void *); static void unregister_proc_table(ctl_table *, struct proc_dir_entry *); #endif @@ -952,7 +952,7 @@ static ctl_table fs_table[] = { .data = &aio_nr, .maxlen = sizeof(aio_nr), .mode = 0444, - .proc_handler = &proc_dointvec, + .proc_handler = &proc_doulongvec_minmax, }, { .ctl_name = FS_AIO_MAX_NR, @@ -960,7 +960,7 @@ static ctl_table fs_table[] = { .data = &aio_max_nr, .maxlen = sizeof(aio_max_nr), .mode = 0644, - .proc_handler = &proc_dointvec, + .proc_handler = &proc_doulongvec_minmax, }, #ifdef CONFIG_INOTIFY { @@ -992,10 +992,51 @@ static ctl_table dev_table[] = { extern void init_irq_proc (void); +static DEFINE_SPINLOCK(sysctl_lock); + +/* called under sysctl_lock */ +static int use_table(struct ctl_table_header *p) +{ + if (unlikely(p->unregistering)) + return 0; + p->used++; + return 1; +} + +/* called under sysctl_lock */ +static void unuse_table(struct ctl_table_header *p) +{ + if (!--p->used) + if (unlikely(p->unregistering)) + complete(p->unregistering); +} + +/* called under sysctl_lock, will reacquire if has to wait */ +static void start_unregistering(struct ctl_table_header *p) +{ + /* + * 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); + spin_lock(&sysctl_lock); + } + /* + * do not remove from the list until nobody holds it; walking the + * list in do_sysctl() relies on that. + */ + list_del_init(&p->ctl_entry); +} + void __init sysctl_init(void) { #ifdef CONFIG_PROC_FS - register_proc_table(root_table, proc_sys_root); + register_proc_table(root_table, proc_sys_root, &root_table_header); init_irq_proc(); #endif } @@ -1004,6 +1045,7 @@ int do_sysctl(int __user *name, int nlen, void __user *oldval, size_t __user *ol void __user *newval, size_t newlen) { struct list_head *tmp; + int error = -ENOTDIR; if (nlen <= 0 || nlen >= CTL_MAXNAME) return -ENOTDIR; @@ -1012,20 +1054,30 @@ int do_sysctl(int __user *name, int nlen, void __user *oldval, size_t __user *ol if (!oldlenp || get_user(old_len, oldlenp)) return -EFAULT; } + spin_lock(&sysctl_lock); tmp = &root_table_header.ctl_entry; do { struct ctl_table_header *head = list_entry(tmp, struct ctl_table_header, ctl_entry); void *context = NULL; - int error = parse_table(name, nlen, oldval, oldlenp, + + if (!use_table(head)) + continue; + + spin_unlock(&sysctl_lock); + + error = parse_table(name, nlen, oldval, oldlenp, newval, newlen, head->ctl_table, &context); kfree(context); + + spin_lock(&sysctl_lock); + unuse_table(head); if (error != -ENOTDIR) - return error; - tmp = tmp->next; - } while (tmp != &root_table_header.ctl_entry); - return -ENOTDIR; + break; + } while ((tmp = tmp->next) != &root_table_header.ctl_entry); + spin_unlock(&sysctl_lock); + return error; } asmlinkage long sys_sysctl(struct __sysctl_args __user *args) @@ -1236,12 +1288,16 @@ struct ctl_table_header *register_sysctl_table(ctl_table * table, return NULL; tmp->ctl_table = table; INIT_LIST_HEAD(&tmp->ctl_entry); + tmp->used = 0; + tmp->unregistering = NULL; + spin_lock(&sysctl_lock); if (insert_at_head) list_add(&tmp->ctl_entry, &root_table_header.ctl_entry); else list_add_tail(&tmp->ctl_entry, &root_table_header.ctl_entry); + spin_unlock(&sysctl_lock); #ifdef CONFIG_PROC_FS - register_proc_table(table, proc_sys_root); + register_proc_table(table, proc_sys_root, tmp); #endif return tmp; } @@ -1255,10 +1311,13 @@ struct ctl_table_header *register_sysctl_table(ctl_table * table, */ void unregister_sysctl_table(struct ctl_table_header * header) { - list_del(&header->ctl_entry); + might_sleep(); + spin_lock(&sysctl_lock); + start_unregistering(header); #ifdef CONFIG_PROC_FS unregister_proc_table(header->ctl_table, proc_sys_root); #endif + spin_unlock(&sysctl_lock); kfree(header); } @@ -1269,7 +1328,7 @@ void unregister_sysctl_table(struct ctl_table_header * header) #ifdef CONFIG_PROC_FS /* Scan the sysctl entries in table and add them all into /proc */ -static void register_proc_table(ctl_table * table, struct proc_dir_entry *root) +static void register_proc_table(ctl_table * table, struct proc_dir_entry *root, void *set) { struct proc_dir_entry *de; int len; @@ -1305,13 +1364,14 @@ static void register_proc_table(ctl_table * table, struct proc_dir_entry *root) de = create_proc_entry(table->procname, mode, root); if (!de) continue; + de->set = set; de->data = (void *) table; if (table->proc_handler) de->proc_fops = &proc_sys_file_operations; } table->de = de; if (de->mode & S_IFDIR) - register_proc_table(table->child, de); + register_proc_table(table->child, de, set); } } @@ -1336,6 +1396,13 @@ static void unregister_proc_table(ctl_table * table, struct proc_dir_entry *root continue; } + /* + * In any case, mark the entry as goner; we'll keep it + * around if it's busy, but we'll know to do nothing with + * its fields. We are under sysctl_lock here. + */ + de->data = NULL; + /* Don't unregister proc entries that are still being used.. */ if (atomic_read(&de->count)) continue; @@ -1349,27 +1416,38 @@ static ssize_t do_rw_proc(int write, struct file * file, char __user * buf, size_t count, loff_t *ppos) { int op; - struct proc_dir_entry *de; + struct proc_dir_entry *de = PDE(file->f_dentry->d_inode); struct ctl_table *table; size_t res; - ssize_t error; - - de = PDE(file->f_dentry->d_inode); - if (!de || !de->data) - return -ENOTDIR; - table = (struct ctl_table *) de->data; - if (!table || !table->proc_handler) - return -ENOTDIR; - op = (write ? 002 : 004); - if (ctl_perm(table, op)) - return -EPERM; + ssize_t error = -ENOTDIR; - res = count; - - error = (*table->proc_handler) (table, write, file, buf, &res, ppos); - if (error) - return error; - return res; + spin_lock(&sysctl_lock); + if (de && de->data && use_table(de->set)) { + /* + * at that point we know that sysctl was not unregistered + * and won't be until we finish + */ + spin_unlock(&sysctl_lock); + table = (struct ctl_table *) de->data; + if (!table || !table->proc_handler) + goto out; + error = -EPERM; + op = (write ? 002 : 004); + if (ctl_perm(table, op)) + goto out; + + /* careful: calling conventions are nasty here */ + res = count; + error = (*table->proc_handler)(table, write, file, + buf, &res, ppos); + if (!error) + error = res; + out: + spin_lock(&sysctl_lock); + unuse_table(de->set); + } + spin_unlock(&sysctl_lock); + return error; } static int proc_opensys(struct inode *inode, struct file *file) @@ -1997,6 +2075,7 @@ int proc_dointvec_jiffies(ctl_table *table, int write, struct file *filp, * @filp: the file structure * @buffer: the user buffer * @lenp: the size of the user buffer + * @ppos: pointer to the file position * * Reads/writes up to table->maxlen/sizeof(unsigned int) integer * values from/to the user buffer, treated as an ASCII string. |