diff options
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 259202637531..0d23e76a0c61 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -711,15 +711,22 @@ EXPORT_SYMBOL_GPL(mmput); * * This changes mm's executable file (shown as symlink /proc/[pid]/exe). * - * Main users are mmput(), sys_execve() and sys_prctl(PR_SET_MM_MAP/EXE_FILE). - * Callers prevent concurrent invocations: in mmput() nobody alive left, - * in execve task is single-threaded, prctl holds mmap_sem exclusively. + * Main users are mmput() and sys_execve(). Callers prevent concurrent + * invocations: in mmput() nobody alive left, in execve task is single + * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the + * mm->exe_file, but does so without using set_mm_exe_file() in order + * to do avoid the need for any locks. */ void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) { - struct file *old_exe_file = rcu_dereference_protected(mm->exe_file, - !atomic_read(&mm->mm_users) || current->in_execve || - lockdep_is_held(&mm->mmap_sem)); + struct file *old_exe_file; + + /* + * It is safe to dereference the exe_file without RCU as + * this function is only called if nobody else can access + * this mm -- see comment above for justification. + */ + old_exe_file = rcu_dereference_raw(mm->exe_file); if (new_exe_file) get_file(new_exe_file); |