diff options
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 22 |
1 files changed, 9 insertions, 13 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index d2e12b6d2b18..7b8b63fb0438 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1396,8 +1396,8 @@ EXPORT_SYMBOL_GPL(mmput_async); * This changes mm's executable file (shown as symlink /proc/[pid]/exe). * * Main users are mmput() and sys_execve(). Callers prevent concurrent - * invocations: in mmput() nobody alive left, in execve task is single - * threaded. + * invocations: in mmput() nobody alive left, in execve it happens before + * the new mm is made visible to anyone. * * Can only fail if new_exe_file != NULL. */ @@ -1432,9 +1432,7 @@ int 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. + * This changes mm's executable file (shown as symlink /proc/[pid]/exe). * * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE). */ @@ -1464,22 +1462,20 @@ int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) return ret; } - /* set the new file, lockless */ ret = deny_write_access(new_exe_file); if (ret) return -EACCES; get_file(new_exe_file); - old_exe_file = xchg(&mm->exe_file, new_exe_file); + /* set the new file */ + mmap_write_lock(mm); + old_exe_file = rcu_dereference_raw(mm->exe_file); + rcu_assign_pointer(mm->exe_file, new_exe_file); + mmap_write_unlock(mm); + if (old_exe_file) { - /* - * Don't race with dup_mmap() getting the file and disallowing - * write access while someone might open the file writable. - */ - mmap_read_lock(mm); allow_write_access(old_exe_file); fput(old_exe_file); - mmap_read_unlock(mm); } return 0; } |