Revert "proc: fix races against execve() of /proc/PID/fd**"

This reverts commit aa6afca5bcaba8101f3ea09d5c3e4100b2b9f0e5.

It escalates of some of the google-chrome SELinux problems with ptrace
("Check failed: pid_ > 0.  Did not find zygote process"), and Andrew
says that it is also causing mystery lockdep reports.

Reported-by: Alex Villacís Lasso <a_villacis@palosanto.com>
Requested-by: James Morris <jmorris@namei.org>
Requested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 2db1bd3173b2d77bb902273173a8ede14bf27f2e..851ba3dcdc290ab6b750793c2840bdffac755de7 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1652,46 +1652,12 @@ out:
        return error;
 }
 
-static int proc_pid_fd_link_getattr(struct vfsmount *mnt, struct dentry *dentry,
-               struct kstat *stat)
-{
-       struct inode *inode = dentry->d_inode;
-       struct task_struct *task = get_proc_task(inode);
-       int rc;
-
-       if (task == NULL)
-               return -ESRCH;
-
-       rc = -EACCES;
-       if (lock_trace(task))
-               goto out_task;
-
-       generic_fillattr(inode, stat);
-       unlock_trace(task);
-       rc = 0;
-out_task:
-       put_task_struct(task);
-       return rc;
-}
-
 static const struct inode_operations proc_pid_link_inode_operations = {
        .readlink       = proc_pid_readlink,
        .follow_link    = proc_pid_follow_link,
        .setattr        = proc_setattr,
 };
 
-static const struct inode_operations proc_fdinfo_link_inode_operations = {
-       .setattr        = proc_setattr,
-       .getattr        = proc_pid_fd_link_getattr,
-};
-
-static const struct inode_operations proc_fd_link_inode_operations = {
-       .readlink       = proc_pid_readlink,
-       .follow_link    = proc_pid_follow_link,
-       .setattr        = proc_setattr,
-       .getattr        = proc_pid_fd_link_getattr,
-};
-
 
 /* building an inode */
 
@@ -1923,61 +1889,49 @@ out:
 
 static int proc_fd_info(struct inode *inode, struct path *path, char *info)
 {
-       struct task_struct *task;
-       struct files_struct *files;
+       struct task_struct *task = get_proc_task(inode);
+       struct files_struct *files = NULL;
        struct file *file;
        int fd = proc_fd(inode);
-       int rc;
-
-       task = get_proc_task(inode);
-       if (!task)
-               return -ENOENT;
-
-       rc = -EACCES;
-       if (lock_trace(task))
-               goto out_task;
-
-       rc = -ENOENT;
-       files = get_files_struct(task);
-       if (files == NULL)
-               goto out_unlock;
 
-       /*
-        * We are not taking a ref to the file structure, so we must
-        * hold ->file_lock.
-        */
-       spin_lock(&files->file_lock);
-       file = fcheck_files(files, fd);
-       if (file) {
-               unsigned int f_flags;
-               struct fdtable *fdt;
-
-               fdt = files_fdtable(files);
-               f_flags = file->f_flags & ~O_CLOEXEC;
-               if (FD_ISSET(fd, fdt->close_on_exec))
-                       f_flags |= O_CLOEXEC;
-
-               if (path) {
-                       *path = file->f_path;
-                       path_get(&file->f_path);
+       if (task) {
+               files = get_files_struct(task);
+               put_task_struct(task);
+       }
+       if (files) {
+               /*
+                * We are not taking a ref to the file structure, so we must
+                * hold ->file_lock.
+                */
+               spin_lock(&files->file_lock);
+               file = fcheck_files(files, fd);
+               if (file) {
+                       unsigned int f_flags;
+                       struct fdtable *fdt;
+
+                       fdt = files_fdtable(files);
+                       f_flags = file->f_flags & ~O_CLOEXEC;
+                       if (FD_ISSET(fd, fdt->close_on_exec))
+                               f_flags |= O_CLOEXEC;
+
+                       if (path) {
+                               *path = file->f_path;
+                               path_get(&file->f_path);
+                       }
+                       if (info)
+                               snprintf(info, PROC_FDINFO_MAX,
+                                        "pos:\t%lli\n"
+                                        "flags:\t0%o\n",
+                                        (long long) file->f_pos,
+                                        f_flags);
+                       spin_unlock(&files->file_lock);
+                       put_files_struct(files);
+                       return 0;
                }
-               if (info)
-                       snprintf(info, PROC_FDINFO_MAX,
-                                "pos:\t%lli\n"
-                                "flags:\t0%o\n",
-                                (long long) file->f_pos,
-                                f_flags);
-               rc = 0;
-       } else
-               rc = -ENOENT;
-       spin_unlock(&files->file_lock);
-       put_files_struct(files);
-
-out_unlock:
-       unlock_trace(task);
-out_task:
-       put_task_struct(task);
-       return rc;
+               spin_unlock(&files->file_lock);
+               put_files_struct(files);
+       }
+       return -ENOENT;
 }
 
 static int proc_fd_link(struct inode *inode, struct path *path)
@@ -2072,7 +2026,7 @@ static struct dentry *proc_fd_instantiate(struct inode *dir,
        spin_unlock(&files->file_lock);
        put_files_struct(files);
 
-       inode->i_op = &proc_fd_link_inode_operations;
+       inode->i_op = &proc_pid_link_inode_operations;
        inode->i_size = 64;
        ei->op.proc_get_link = proc_fd_link;
        d_set_d_op(dentry, &tid_fd_dentry_operations);
@@ -2104,12 +2058,7 @@ static struct dentry *proc_lookupfd_common(struct inode *dir,
        if (fd == ~0U)
                goto out;
 
-       result = ERR_PTR(-EACCES);
-       if (lock_trace(task))
-               goto out;
-
        result = instantiate(dir, dentry, task, &fd);
-       unlock_trace(task);
 out:
        put_task_struct(task);
 out_no_task:
@@ -2129,28 +2078,23 @@ static int proc_readfd_common(struct file * filp, void * dirent,
        retval = -ENOENT;
        if (!p)
                goto out_no_task;
-
-       retval = -EACCES;
-       if (lock_trace(p))
-               goto out;
-
        retval = 0;
 
        fd = filp->f_pos;
        switch (fd) {
                case 0:
                        if (filldir(dirent, ".", 1, 0, inode->i_ino, DT_DIR) < 0)
-                               goto out_unlock;
+                               goto out;
                        filp->f_pos++;
                case 1:
                        ino = parent_ino(dentry);
                        if (filldir(dirent, "..", 2, 1, ino, DT_DIR) < 0)
-                               goto out_unlock;
+                               goto out;
                        filp->f_pos++;
                default:
                        files = get_files_struct(p);
                        if (!files)
-                               goto out_unlock;
+                               goto out;
                        rcu_read_lock();
                        for (fd = filp->f_pos-2;
                             fd < files_fdtable(files)->max_fds;
@@ -2174,9 +2118,6 @@ static int proc_readfd_common(struct file * filp, void * dirent,
                        rcu_read_unlock();
                        put_files_struct(files);
        }
-
-out_unlock:
-       unlock_trace(p);
 out:
        put_task_struct(p);
 out_no_task:
@@ -2254,7 +2195,6 @@ static struct dentry *proc_fdinfo_instantiate(struct inode *dir,
        ei->fd = fd;
        inode->i_mode = S_IFREG | S_IRUSR;
        inode->i_fop = &proc_fdinfo_file_operations;
-       inode->i_op = &proc_fdinfo_link_inode_operations;
        d_set_d_op(dentry, &tid_fd_dentry_operations);
        d_add(dentry, inode);
        /* Close the race of the process dying before we return the dentry */