Messages in this thread Patch in this message | | | Date | Wed, 11 Oct 2023 12:33:27 -0700 | From | Nicolin Chen <> | 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 09:26:12PM +0800, Tina Zhang wrote: > On 10/11/23 20:39, Jason Gunthorpe wrote: > > 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. > Good catch. > > Thanks, > -Tina > > > > Keep mm_pasid_init() and add zeroing the new pointer to it.
Yea, testing with this sees no more WARN_ON:
--------------------------------------------------------- diff --git a/include/linux/iommu.h b/include/linux/iommu.h index 3d782fd0f485..4bc3c49cdaf9 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -1208,2 +1208,6 @@ static inline bool tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream #ifdef CONFIG_IOMMU_SVA +static inline void mm_pasid_init(struct mm_struct *mm) +{ + mm->iommu_mm = NULL; +} static inline bool mm_valid_pasid(struct mm_struct *mm) @@ -1240,2 +1244,3 @@ static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle) } +static inline void mm_pasid_init(struct mm_struct *mm) {} static inline bool mm_valid_pasid(struct mm_struct *mm) { return false; } diff --git a/kernel/fork.c b/kernel/fork.c index f06392dd1ca8..d2e12b6d2b18 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1276,2 +1276,3 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, mm_init_owner(mm, p); + mm_pasid_init(mm); RCU_INIT_POINTER(mm->exe_file, NULL); --------------------------------------------------------- I'll confirm with v7 too.
Thanks Nicolin
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