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authorChristian Brauner <brauner@kernel.org>2024-07-31 12:01:12 +0200
committerChristian Brauner <brauner@kernel.org>2024-08-12 22:03:26 +0200
commit3b5bbe798b2451820e74243b738268f51901e7d0 (patch)
tree41c7dc949f52c5b19074dd1e732cd4167e0cc6e6 /kernel
parent889ced4c9388785952d78d20d338bda2df209bb5 (diff)
pidfd: prevent creation of pidfds for kthreads
It's currently possible to create pidfds for kthreads but it is unclear what that is supposed to mean. Until we have use-cases for it and we figured out what behavior we want block the creation of pidfds for kthreads. Link: https://lore.kernel.org/r/20240731-gleis-mehreinnahmen-6bbadd128383@brauner Fixes: 32fcb426ec00 ("pid: add pidfd_open()") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/fork.c25
1 files changed, 22 insertions, 3 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index cc760491f201..18bdc87209d0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2053,11 +2053,24 @@ static int __pidfd_prepare(struct pid *pid, unsigned int flags, struct file **re
*/
int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret)
{
- bool thread = flags & PIDFD_THREAD;
-
- if (!pid || !pid_has_task(pid, thread ? PIDTYPE_PID : PIDTYPE_TGID))
+ if (!pid)
return -EINVAL;
+ scoped_guard(rcu) {
+ struct task_struct *tsk;
+
+ if (flags & PIDFD_THREAD)
+ tsk = pid_task(pid, PIDTYPE_PID);
+ else
+ tsk = pid_task(pid, PIDTYPE_TGID);
+ if (!tsk)
+ return -EINVAL;
+
+ /* Don't create pidfds for kernel threads for now. */
+ if (tsk->flags & PF_KTHREAD)
+ return -EINVAL;
+ }
+
return __pidfd_prepare(pid, flags, ret);
}
@@ -2403,6 +2416,12 @@ __latent_entropy struct task_struct *copy_process(
if (clone_flags & CLONE_PIDFD) {
int flags = (clone_flags & CLONE_THREAD) ? PIDFD_THREAD : 0;
+ /* Don't create pidfds for kernel threads for now. */
+ if (args->kthread) {
+ retval = -EINVAL;
+ goto bad_fork_free_pid;
+ }
+
/* Note that no task has been attached to @pid yet. */
retval = __pidfd_prepare(pid, flags, &pidfile);
if (retval < 0)