fork: Stop allowing kthreads to call execve
Now that kernel_execve is no longer called from kernel threads stop
supporting kernel threads calling kernel_execve.
Remove the code for converting a kthread to a normal thread in execve.
Document the restriction that kthreads may not call kernel_execve by
having kernel_execve fail if called by a kthread.
Link: https://lkml.kernel.org/r/20220506141512.516114-7-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/fs/exec.c b/fs/exec.c
index 75eb6e0..9c5260e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1308,7 +1308,7 @@ int begin_new_exec(struct linux_binprm * bprm)
if (retval)
goto out_unlock;
- me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
+ me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC |
PF_NOFREEZE | PF_NO_SETAFFINITY);
flush_thread();
me->personality &= ~bprm->per_clear;
@@ -1953,8 +1953,8 @@ int kernel_execve(const char *kernel_filename,
int fd = AT_FDCWD;
int retval;
- if (WARN_ON_ONCE((current->flags & PF_KTHREAD) &&
- (current->worker_private)))
+ /* It is non-sense for kernel threads to call execve */
+ if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
return -EINVAL;
filename = getname_kernel(kernel_filename);
