Messages in this thread Patch in this message | | | Date | Thu, 11 Jun 2020 13:02:21 +0200 | From | Christian Brauner <> | Subject | vdso_join_timens() question |
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Hey,
I'm about to finish a patch to add CLONE_NEWTIME support to setns(). Since setns() now allows to attach to a multiple namespaces at the same time I've also reworked it to be atomic (already upstream). Either all namespaces are switched or no namespace is switched. All namespaces basically now have a commit mode after which installation should ideally not fail anymore. That could work for CLONE_NEWTIME too, I think. The only blocker to this is vdso_join_timens() which can fail due to mmap_write_lock_killable().
Is it possible to change this to mmap_write_lock()? So sm like:
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index ea7c1f0b79df..5c5b4cc61fce 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -144,8 +144,7 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) struct mm_struct *mm = task->mm; struct vm_area_struct *vma;
- if (mmap_write_lock_killable(mm)) - return -EINTR; + mmap_write_lock(mm);
for (vma = mm->mmap; vma; vma = vma->vm_next) { unsigned long size = vma->vm_end - vma->vm_start; vdso_join_timens() is called in two places. Once during fork() and once during timens_install(). I would only need the mmap_write_lock() change for the latter. So alternatively we could have:
__vdso_join_timens_unlocked()
and then have/expose:
vdso_join_timens_fork() { if (mmap_write_lock_killable(mm)) return -EINTR; __vdso_join_timens_unlocked() mmap_write_unlock(mm); } and
vdso_join_timens_install() { mmap_write_lock(mm); __vdso_join_timens_unlocked() mmap_write_unlock(mm); } Thanks! Christian
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