680baacbca
a) instead of storing the symlink body (via nd_set_link()) and returning an opaque pointer later passed to ->put_link(), ->follow_link() _stores_ that opaque pointer (into void * passed by address by caller) and returns the symlink body. Returning ERR_PTR() on error, NULL on jump (procfs magic symlinks) and pointer to symlink body for normal symlinks. Stored pointer is ignored in all cases except the last one. Storing NULL for opaque pointer (or not storing it at all) means no call of ->put_link(). b) the body used to be passed to ->put_link() implicitly (via nameidata). Now only the opaque pointer is. In the cases when we used the symlink body to free stuff, ->follow_link() now should store it as opaque pointer in addition to returning it. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
83 lines
2.0 KiB
C
83 lines
2.0 KiB
C
#include <linux/sched.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/self:
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*/
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static int proc_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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char tmp[PROC_NUMBUF];
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if (!tgid)
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return -ENOENT;
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sprintf(tmp, "%d", tgid);
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return readlink_copy(buffer, buflen, tmp);
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}
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static const char *proc_self_follow_link(struct dentry *dentry, void **cookie, 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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char *name;
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if (!tgid)
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return ERR_PTR(-ENOENT);
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/* 11 for max length of signed int in decimal + NULL term */
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name = kmalloc(12, GFP_KERNEL);
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if (!name)
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return ERR_PTR(-ENOMEM);
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sprintf(name, "%d", tgid);
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return *cookie = name;
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}
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static const struct inode_operations proc_self_inode_operations = {
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.readlink = proc_self_readlink,
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.follow_link = proc_self_follow_link,
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.put_link = kfree_put_link,
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};
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static unsigned self_inum;
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int proc_setup_self(struct super_block *s)
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{
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struct inode *root_inode = d_inode(s->s_root);
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struct pid_namespace *ns = s->s_fs_info;
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struct dentry *self;
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mutex_lock(&root_inode->i_mutex);
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self = d_alloc_name(s->s_root, "self");
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if (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 = 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_self_inode_operations;
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d_add(self, inode);
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} else {
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dput(self);
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self = ERR_PTR(-ENOMEM);
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}
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} else {
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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(self)) {
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pr_err("proc_fill_super: can't allocate /proc/self\n");
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return PTR_ERR(self);
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}
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ns->proc_self = self;
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return 0;
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}
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void __init proc_self_init(void)
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{
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proc_alloc_inum(&self_inum);
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}
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