mm: do not initialize TLB stack vma's with vma_init()

torvalds · torvalds · commit 8b11ec1b5ffb · 2018-08-01T13:43:38.000-07:00
Commit 2c4541e ("mm: use vma_init() to initialize VMAs on stack and data segments") tried to initialize various left-over ad-hoc vma's "properly", but actually made things worse for the temporary vma's used for TLB flushing. vma_init() doesn't actually initialize all of the vma, just a few fields, so doing something like - struct vm_area_struct vma = { .vm_mm = tlb->mm, }; + struct vm_area_struct vma; + + vma_init(&vma, tlb->mm); was actually very bad: instead of having a nicely initialized vma with every field but "vm_mm" zeroed, you'd have an entirely uninitialized vma with only a couple of fields initialized. And they weren't even fields that the code in question mostly cared about. The flush_tlb_range() function takes a "struct vma" rather than a "struct mm_struct", because a few architectures actually care about what kind of range it is - being able to only do an ITLB flush if it's a range that doesn't have data accesses enabled, for example. And all the normal users already have the vma for doing the range invalidation. But a few people want to call flush_tlb_range() with a range they just made up, so they also end up using a made-up vma. x86 just has a special "flush_tlb_mm_range()" function for this, but other architectures (arm and ia64) do the "use fake vma" thing instead, and thus got caught up in the vma_init() changes. At the same time, the TLB flushing code really doesn't care about most other fields in the vma, so vma_init() is just unnecessary and pointless. This fixes things by having an explicit "this is just an initializer for the TLB flush" initializer macro, which is used by the arm/arm64/ia64 people who mis-use this interface with just a dummy vma. Fixes: 2c4541e ("mm: use vma_init() to initialize VMAs on stack and data segments") Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/arm/mach-rpc/ecard.c b/arch/arm/mach-rpc/ecard.c
@@ -212,7 +212,7 @@ static DEFINE_MUTEX(ecard_mutex);
  */
 static void ecard_init_pgtables(struct mm_struct *mm)
 {
-	struct vm_area_struct vma;
+	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, VM_EXEC);
 
 	/* We want to set up the page tables for the following mapping:
 	 *  Virtual	Physical
@@ -237,9 +237,6 @@ static void ecard_init_pgtables(struct mm_struct *mm)
 
 	memcpy(dst_pgd, src_pgd, sizeof(pgd_t) * (EASI_SIZE / PGDIR_SIZE));
 
-	vma_init(&vma, mm);
-	vma.vm_flags = VM_EXEC;
-
 	flush_tlb_range(&vma, IO_START, IO_START + IO_SIZE);
 	flush_tlb_range(&vma, EASI_START, EASI_START + EASI_SIZE);
 }
diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
@@ -37,9 +37,7 @@ static inline void __tlb_remove_table(void *_table)
 
 static inline void tlb_flush(struct mmu_gather *tlb)
 {
-	struct vm_area_struct vma;
-
-	vma_init(&vma, tlb->mm);
+	struct vm_area_struct vma = TLB_FLUSH_VMA(tlb->mm, 0);
 
 	/*
 	 * The ASID allocator will either invalidate the ASID or mark
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
@@ -108,13 +108,10 @@ static pte_t get_clear_flush(struct mm_struct *mm,
 			     unsigned long pgsize,
 			     unsigned long ncontig)
 {
-	struct vm_area_struct vma;
 	pte_t orig_pte = huge_ptep_get(ptep);
 	bool valid = pte_valid(orig_pte);
 	unsigned long i, saddr = addr;
 
-	vma_init(&vma, mm);
-
 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {
 		pte_t pte = ptep_get_and_clear(mm, addr, ptep);
 
@@ -127,8 +124,10 @@ static pte_t get_clear_flush(struct mm_struct *mm,
 			orig_pte = pte_mkdirty(orig_pte);
 	}
 
-	if (valid)
+	if (valid) {
+		struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
 		flush_tlb_range(&vma, saddr, addr);
+	}
 	return orig_pte;
 }
 
@@ -147,10 +146,9 @@ static void clear_flush(struct mm_struct *mm,
 			     unsigned long pgsize,
 			     unsigned long ncontig)
 {
-	struct vm_area_struct vma;
+	struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
 	unsigned long i, saddr = addr;
 
-	vma_init(&vma, mm);
 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
 		pte_clear(mm, addr, ptep);
 
diff --git a/arch/ia64/include/asm/tlb.h b/arch/ia64/include/asm/tlb.h
@@ -115,12 +115,11 @@ ia64_tlb_flush_mmu_tlbonly(struct mmu_gather *tlb, unsigned long start, unsigned
 		flush_tlb_all();
 	} else {
 		/*
-		 * XXX fix me: flush_tlb_range() should take an mm pointer instead of a
-		 * vma pointer.
+		 * flush_tlb_range() takes a vma instead of a mm pointer because
+		 * some architectures want the vm_flags for ITLB/DTLB flush.
 		 */
-		struct vm_area_struct vma;
+		struct vm_area_struct vma = TLB_FLUSH_VMA(tlb->mm, 0);
 
-		vma_init(&vma, tlb->mm);
 		/* flush the address range from the tlb: */
 		flush_tlb_range(&vma, start, end);
 		/* now flush the virt. page-table area mapping the address range: */
diff --git a/include/linux/mm.h b/include/linux/mm.h
@@ -466,6 +466,9 @@ static inline void vma_set_anonymous(struct vm_area_struct *vma)
 	vma->vm_ops = NULL;
 }
 
+/* flush_tlb_range() takes a vma, not a mm, and can care about flags */
+#define TLB_FLUSH_VMA(mm,flags) { .vm_mm = (mm), .vm_flags = (flags) }
+
 struct mmu_gather;
 struct inode;
 

Original file line number	Diff line number	Diff line change
`@@ -37,9 +37,7 @@ static inline void __tlb_remove_table(void *_table)`
`37`	`37`
`38`	`38`	`static inline void tlb_flush(struct mmu_gather *tlb)`
`39`	`39`	`{`
`40`		`- struct vm_area_struct vma;`
`41`		`-`
`42`		`- vma_init(&vma, tlb->mm);`
	`40`	`+ struct vm_area_struct vma = TLB_FLUSH_VMA(tlb->mm, 0);`
`43`	`41`
`44`	`42`	`/*`
`45`	`43`	`* The ASID allocator will either invalidate the ASID or mark`
Original file line number	Diff line number	Diff line change
`@@ -466,6 +466,9 @@ static inline void vma_set_anonymous(struct vm_area_struct *vma)`
`466`	`466`	`vma->vm_ops = NULL;`
`467`	`467`	`}`
`468`	`468`
	`469`	`+/* flush_tlb_range() takes a vma, not a mm, and can care about flags */`
	`470`	`+#define TLB_FLUSH_VMA(mm,flags) { .vm_mm = (mm), .vm_flags = (flags) }`
	`471`	`+`
`469`	`472`	`struct mmu_gather;`
`470`	`473`	`struct inode;`
`471`	`474`