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mmu_gather: Force tlb-flush VM_PFNMAP vmas

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Jann reported a race between munmap() and unmap_mapping_range(), where
unmap_mapping_range() will no-op once unmap_vmas() has unlinked the
VMA; however munmap() will not yet have invalidated the TLBs.

Therefore unmap_mapping_range() will complete while there are still
(stale) TLB entries for the specified range.

Mitigate this by force flushing TLBs for VM_PFNMAP ranges.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Zijlstra 2022-07-08 09:18:06 +02:00 committed by Linus Torvalds
parent 18ba064e42
commit b67fbebd4c
1 changed files with 17 additions and 16 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

29
include/asm-generic/tlb.h
View file

@ -303,6 +303,7 @@ struct mmu_gather {
*/ */
unsigned int vma_exec : 1; unsigned int vma_exec : 1;
unsigned int vma_huge : 1; unsigned int vma_huge : 1;
unsigned int vma_pfn : 1;
unsigned int batch_count; unsigned int batch_count;
@ -373,7 +374,6 @@ tlb_update_vma_flags(struct mmu_gather *tlb, struct vm_area_struct *vma) { }
#else /* CONFIG_MMU_GATHER_NO_RANGE */ #else /* CONFIG_MMU_GATHER_NO_RANGE */
#ifndef tlb_flush #ifndef tlb_flush
/* /*
* When an architecture does not provide its own tlb_flush() implementation * When an architecture does not provide its own tlb_flush() implementation
* but does have a reasonably efficient flush_vma_range() implementation * but does have a reasonably efficient flush_vma_range() implementation
@ -393,6 +393,9 @@ static inline void tlb_flush(struct mmu_gather *tlb)
flush_tlb_range(&vma, tlb->start, tlb->end); flush_tlb_range(&vma, tlb->start, tlb->end);
} }
} }
#endif
#endif /* CONFIG_MMU_GATHER_NO_RANGE */
static inline void static inline void
tlb_update_vma_flags(struct mmu_gather *tlb, struct vm_area_struct *vma) tlb_update_vma_flags(struct mmu_gather *tlb, struct vm_area_struct *vma)
@ -410,17 +413,9 @@ tlb_update_vma_flags(struct mmu_gather *tlb, struct vm_area_struct *vma)
*/ */
tlb->vma_huge = is_vm_hugetlb_page(vma); tlb->vma_huge = is_vm_hugetlb_page(vma);
tlb->vma_exec = !!(vma->vm_flags & VM_EXEC); tlb->vma_exec = !!(vma->vm_flags & VM_EXEC);
tlb->vma_pfn = !!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP));
} }
#else
static inline void
tlb_update_vma_flags(struct mmu_gather *tlb, struct vm_area_struct *vma) { }
#endif
#endif /* CONFIG_MMU_GATHER_NO_RANGE */
static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb) static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
{ {
/* /*
@ -507,16 +502,22 @@ static inline void tlb_start_vma(struct mmu_gather *tlb, struct vm_area_struct *
static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma) static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
{ {
if (tlb->fullmm || IS_ENABLED(CONFIG_MMU_GATHER_MERGE_VMAS)) if (tlb->fullmm)
return; return;
/*
* VM_PFNMAP is more fragile because the core mm will not track the
* page mapcount -- there might not be page-frames for these PFNs after
* all. Force flush TLBs for such ranges to avoid munmap() vs
* unmap_mapping_range() races.
*/
if (tlb->vma_pfn || !IS_ENABLED(CONFIG_MMU_GATHER_MERGE_VMAS)) {
/* /*
* Do a TLB flush and reset the range at VMA boundaries; this avoids * Do a TLB flush and reset the range at VMA boundaries; this avoids
* the ranges growing with the unused space between consecutive VMAs, * the ranges growing with the unused space between consecutive VMAs.
* but also the mmu_gather::vma_* flags from tlb_start_vma() rely on
* this.
*/ */
tlb_flush_mmu_tlbonly(tlb); tlb_flush_mmu_tlbonly(tlb);
}
} }
/* /*