New locking/refcounting for fs_struct
[linux-2.6.git] / fs / exec.c
index c5128fb..07a0596 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1056,16 +1056,18 @@ EXPORT_SYMBOL(install_exec_creds);
  * - the caller must hold current->cred_exec_mutex to protect against
  *   PTRACE_ATTACH
  */
-void check_unsafe_exec(struct linux_binprm *bprm)
+int check_unsafe_exec(struct linux_binprm *bprm)
 {
        struct task_struct *p = current, *t;
        unsigned long flags;
        unsigned n_fs, n_sighand;
+       int res = 0;
 
        bprm->unsafe = tracehook_unsafe_exec(p);
 
        n_fs = 1;
        n_sighand = 1;
+       write_lock(&p->fs->lock);
        lock_task_sighand(p, &flags);
        for (t = next_thread(p); t != p; t = next_thread(t)) {
                if (t->fs == p->fs)
@@ -1073,11 +1075,19 @@ void check_unsafe_exec(struct linux_binprm *bprm)
                n_sighand++;
        }
 
-       if (atomic_read(&p->fs->count) > n_fs ||
-           atomic_read(&p->sighand->count) > n_sighand)
+       if (p->fs->users > n_fs ||
+           atomic_read(&p->sighand->count) > n_sighand) {
                bprm->unsafe |= LSM_UNSAFE_SHARE;
+       } else {
+               if (p->fs->in_exec)
+                       res = -EAGAIN;
+               p->fs->in_exec = 1;
+       }
 
        unlock_task_sighand(p, &flags);
+       write_unlock(&p->fs->lock);
+
+       return res;
 }
 
 /* 
@@ -1296,12 +1306,15 @@ int do_execve(char * filename,
        bprm->cred = prepare_exec_creds();
        if (!bprm->cred)
                goto out_unlock;
-       check_unsafe_exec(bprm);
+
+       retval = check_unsafe_exec(bprm);
+       if (retval)
+               goto out_unlock;
 
        file = open_exec(filename);
        retval = PTR_ERR(file);
        if (IS_ERR(file))
-               goto out_unlock;
+               goto out_unmark;
 
        sched_exec();
 
@@ -1344,6 +1357,9 @@ int do_execve(char * filename,
                goto out;
 
        /* execve succeeded */
+       write_lock(&current->fs->lock);
+       current->fs->in_exec = 0;
+       write_unlock(&current->fs->lock);
        current->in_execve = 0;
        mutex_unlock(&current->cred_exec_mutex);
        acct_update_integrals(current);
@@ -1362,6 +1378,11 @@ out_file:
                fput(bprm->file);
        }
 
+out_unmark:
+       write_lock(&current->fs->lock);
+       current->fs->in_exec = 0;
+       write_unlock(&current->fs->lock);
+
 out_unlock:
        current->in_execve = 0;
        mutex_unlock(&current->cred_exec_mutex);