0097875bd4
/proc/thread-self is derived from /proc/self. /proc/thread-self points to the directory in proc containing information about the current thread. This funtionality has been missing for a long time, and is tricky to implement in userspace as gettid() is not exported by glibc. More importantly this allows fixing defects in /proc/mounts and /proc/net where in a threaded application today they wind up being empty files when only the initial pthread has exited, causing problems for other threads. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
85 lines
2.3 KiB
C
85 lines
2.3 KiB
C
#include <linux/sched.h>
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#include <linux/namei.h>
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#include <linux/slab.h>
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#include <linux/pid_namespace.h>
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#include "internal.h"
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/*
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* /proc/thread_self:
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*/
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static int proc_thread_self_readlink(struct dentry *dentry, char __user *buffer,
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int buflen)
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{
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struct pid_namespace *ns = dentry->d_sb->s_fs_info;
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pid_t tgid = task_tgid_nr_ns(current, ns);
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pid_t pid = task_pid_nr_ns(current, ns);
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char tmp[PROC_NUMBUF + 6 + PROC_NUMBUF];
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if (!pid)
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return -ENOENT;
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sprintf(tmp, "%d/task/%d", tgid, pid);
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return readlink_copy(buffer, buflen, tmp);
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}
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static void *proc_thread_self_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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struct pid_namespace *ns = dentry->d_sb->s_fs_info;
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pid_t tgid = task_tgid_nr_ns(current, ns);
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pid_t pid = task_pid_nr_ns(current, ns);
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char *name = ERR_PTR(-ENOENT);
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if (pid) {
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name = kmalloc(PROC_NUMBUF + 6 + PROC_NUMBUF, GFP_KERNEL);
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if (!name)
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name = ERR_PTR(-ENOMEM);
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else
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sprintf(name, "%d/task/%d", tgid, pid);
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}
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nd_set_link(nd, name);
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return NULL;
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}
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static const struct inode_operations proc_thread_self_inode_operations = {
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.readlink = proc_thread_self_readlink,
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.follow_link = proc_thread_self_follow_link,
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.put_link = kfree_put_link,
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};
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static unsigned thread_self_inum;
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int proc_setup_thread_self(struct super_block *s)
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{
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struct inode *root_inode = s->s_root->d_inode;
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struct pid_namespace *ns = s->s_fs_info;
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struct dentry *thread_self;
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mutex_lock(&root_inode->i_mutex);
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thread_self = d_alloc_name(s->s_root, "thread-self");
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if (thread_self) {
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struct inode *inode = new_inode_pseudo(s);
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if (inode) {
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inode->i_ino = thread_self_inum;
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inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
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inode->i_mode = S_IFLNK | S_IRWXUGO;
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inode->i_uid = GLOBAL_ROOT_UID;
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inode->i_gid = GLOBAL_ROOT_GID;
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inode->i_op = &proc_thread_self_inode_operations;
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d_add(thread_self, inode);
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} else {
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dput(thread_self);
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thread_self = ERR_PTR(-ENOMEM);
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}
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} else {
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thread_self = ERR_PTR(-ENOMEM);
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}
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mutex_unlock(&root_inode->i_mutex);
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if (IS_ERR(thread_self)) {
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pr_err("proc_fill_super: can't allocate /proc/thread_self\n");
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return PTR_ERR(thread_self);
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}
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ns->proc_thread_self = thread_self;
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return 0;
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}
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void __init proc_thread_self_init(void)
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{
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proc_alloc_inum(&thread_self_inum);
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}
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