Messages in this thread | | | Date | Wed, 11 Oct 2023 09:39:10 -0300 | From | Jason Gunthorpe <> | Subject | Re: [v6 PATCH 4/5] iommu: Support mm PASID 1:n with sva domains |
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On Wed, Oct 11, 2023 at 02:51:31PM +0800, Tina Zhang wrote:
> diff --git a/kernel/fork.c b/kernel/fork.c > index 3b6d20dfb9a8..985403a7a747 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1277,7 +1277,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, > mm_init_cpumask(mm); > mm_init_aio(mm); > mm_init_owner(mm, p); > - mm_pasid_init(mm); > RCU_INIT_POINTER(mm->exe_file, NULL); > mmu_notifier_subscriptions_init(mm); > init_tlb_flush_pending(mm);
Nicolin debugged his crash report last night and sent me the details.
This hunk is the cause of the bug that Nicolin reported.
The dup_mm() flow does:
static struct mm_struct *dup_mm(struct task_struct *tsk, struct mm_struct *oldmm) { struct mm_struct *mm; int err;
mm = allocate_mm(); if (!mm) goto fail_nomem;
memcpy(mm, oldmm, sizeof(*mm));
if (!mm_init(mm, tsk, mm->user_ns)) goto fail_nomem;
It is essential that mm_pasid_init() zero the new pointer otherwise, due to the memcpy, after a fork two mm structs will point to the same thing and one will UAF/doube free.
Keep mm_pasid_init() and add zeroing the new pointer to it.
Jason
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