diff options
| author | Christian Brauner <brauner@kernel.org> | 2025-04-04 16:06:55 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-04-07 09:38:24 +0200 |
| commit | 1e940fff94374d04b6c34f896ed9fbad3d2fb706 (patch) | |
| tree | b8b36d1b847d960dfb7bb9d76b4e477b65ebd656 /kernel/fork.c | |
| parent | 0af2f6be1b4281385b618cb86ad946eded089ac8 (diff) | |
| parent | 4fc3f73c16dae0211f31a963eedfb921f8366f57 (diff) | |
Merge patch series "pidfd: improve uapi when task isn't found"
Christian Brauner <brauner@kernel.org> says:
We currently report EINVAL whenever a struct pid has no tasked attached
anymore thereby conflating two concepts:
(1) The task has already been reaped.
(2) The caller requested a pidfd for a thread-group leader but the pid
actually references a struct pid that isn't used as a thread-group
leader.
This is causing issues for non-threaded workloads as in [1] where they
expect ESRCH to be reported, not EINVAL. I think that's a very resonable
assumption.
This patch tries to allow userspace to distinguish between (1) and (2).
This is racy of course but that shouldn't matter.
* patches from https://lore.kernel.org/r/20250403-work-pidfd-fixes-v1-0-a123b6ed6716@kernel.org:
selftest/pidfd: add test for thread-group leader pidfd open for thread
pidfd: improve uapi when task isn't found
pidfd: remove unneeded NULL check from pidfd_prepare()
selftests/pidfd: adapt to recent changes
Link: https://lore.kernel.org/r/20250403-work-pidfd-fixes-v1-0-a123b6ed6716@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index c4b26cd8998b..4a2080b968c8 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2108,10 +2108,27 @@ 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; + int err = 0; - if (!pid || !pid_has_task(pid, thread ? PIDTYPE_PID : PIDTYPE_TGID)) - return -EINVAL; + if (!(flags & PIDFD_THREAD)) { + /* + * If this is struct pid isn't used as a thread-group + * leader pid but the caller requested to create a + * thread-group leader pidfd then report ENOENT to the + * caller as a hint. + */ + if (!pid_has_task(pid, PIDTYPE_TGID)) + err = -ENOENT; + } + + /* + * If this wasn't a thread-group leader struct pid or the task + * got reaped in the meantime report -ESRCH to userspace. + */ + if (!pid_has_task(pid, PIDTYPE_PID)) + err = -ESRCH; + if (err) + return err; return __pidfd_prepare(pid, flags, ret); } |