diff options
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 44 |
1 files changed, 41 insertions, 3 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 44f4c2d83763..f4ac883c4a1e 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1148,9 +1148,7 @@ void mmput_async(struct mm_struct *mm) * * 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 avoid the need for any locks. + * threaded. */ void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) { @@ -1171,6 +1169,46 @@ void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) } /** + * replace_mm_exe_file - replace a reference to the mm's executable file + * + * This changes mm's executable file (shown as symlink /proc/[pid]/exe), + * dealing with concurrent invocation and without grabbing the mmap lock in + * write mode. + * + * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE). + */ +int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) +{ + struct vm_area_struct *vma; + struct file *old_exe_file; + int ret = 0; + + /* Forbid mm->exe_file change if old file still mapped. */ + old_exe_file = get_mm_exe_file(mm); + if (old_exe_file) { + mmap_read_lock(mm); + for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) { + if (!vma->vm_file) + continue; + if (path_equal(&vma->vm_file->f_path, + &old_exe_file->f_path)) + ret = -EBUSY; + } + mmap_read_unlock(mm); + fput(old_exe_file); + if (ret) + return ret; + } + + /* set the new file, lockless */ + get_file(new_exe_file); + old_exe_file = xchg(&mm->exe_file, new_exe_file); + if (old_exe_file) + fput(old_exe_file); + return 0; +} + +/** * get_mm_exe_file - acquire a reference to the mm's executable file * * Returns %NULL if mm has no associated executable file. |