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charset="utf-8" All callers of follow_pfnmap_start() except s390_pci_mmio_write() are following it, if they are doing a write, with a check that args.writable is true; for s390_pci_mmio_write() that's a bug. Most of them return -EFAULT if it is not, but because follow_pfnmap_start() returned success, they do not attempt to upgrade the page from read-only to read-write with fixup_user_fault(). Pull the check directly into follow_pfnmap_start() through another input parameter args.write_fault; this eliminates the need to do it in the caller and, for callers that do use fixup_user_fault(), lets it attempt to upgrade the page. The change in return code to -EFAULT is okay: - s390 is the only one to have a functional change in this respect; but EINVAL is only documented for "Invalid length argument", while "The address in mmio_addr is invalid" should already return EFAULT (https://www.man7.org/linux/man-pages/man2/s390_pci_mmio_read.2.html) - for VFIO and ACRN, -EFAULT was returned already - for KVM, -EFAULT is eaten - for generic_access_phys() the caller is __access_remote_vm() which does not care about the error code. Reported-by: Sergio Lopez Link: https://lore.kernel.org/kvm/CAAiTLFU1ALsDoJoKW3d9bUvv990AozAoX=3DbEHm= fnG54qyBAHFg@mail.gmail.com/ Signed-off-by: Paolo Bonzini Reported-by: without Fixes: is odd. --- Sergio, this is half of the fix for your issue. Please test both patches together if possible. arch/s390/pci/pci_mmio.c | 2 ++ drivers/vfio/vfio_iommu_type1.c | 17 +++++---- drivers/virt/acrn/mm.c | 10 +----- include/linux/mm.h | 3 ++ mm/memory.c | 62 ++++++++++++++++++++------------- virt/kvm/kvm_main.c | 22 ++++++------ 6 files changed, 64 insertions(+), 52 deletions(-) diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c index 51e7a28af899..526f80b8fb3b 100644 --- a/arch/s390/pci/pci_mmio.c +++ b/arch/s390/pci/pci_mmio.c @@ -180,6 +180,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, mmi= o_addr, =20 args.address =3D mmio_addr; args.vma =3D vma; + args.write_fault =3D true; ret =3D follow_pfnmap_start(&args); if (ret) { fixup_user_fault(current->mm, mmio_addr, FAULT_FLAG_WRITE, NULL); @@ -332,6 +333,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_read, unsigned long, mmio= _addr, =20 args.vma =3D vma; args.address =3D mmio_addr; + args.write_fault =3D false; ret =3D follow_pfnmap_start(&args); if (ret) { fixup_user_fault(current->mm, mmio_addr, 0, NULL); diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type= 1.c index c8151ba54de3..9ee92820b4de 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -541,7 +541,11 @@ static int follow_fault_pfn(struct vm_area_struct *vma= , struct mm_struct *mm, unsigned long vaddr, unsigned long *pfn, unsigned long *addr_mask, bool write_fault) { - struct follow_pfnmap_args args =3D { .vma =3D vma, .address =3D vaddr }; + struct follow_pfnmap_args args =3D { + .vma =3D vma, + .address =3D vaddr, + .write_fault =3D write_fault + }; int ret; =20 ret =3D follow_pfnmap_start(&args); @@ -563,15 +567,10 @@ static int follow_fault_pfn(struct vm_area_struct *vm= a, struct mm_struct *mm, return ret; } =20 - if (write_fault && !args.writable) { - ret =3D -EFAULT; - } else { - *pfn =3D args.pfn; - *addr_mask =3D args.addr_mask; - } - + *pfn =3D args.pfn; + *addr_mask =3D args.addr_mask; follow_pfnmap_end(&args); - return ret; + return 0; } =20 /* diff --git a/drivers/virt/acrn/mm.c b/drivers/virt/acrn/mm.c index 5bca500a83e0..b057e78ef3f4 100644 --- a/drivers/virt/acrn/mm.c +++ b/drivers/virt/acrn/mm.c @@ -177,7 +177,6 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_= memmap *memmap) vma =3D vma_lookup(current->mm, memmap->vma_base); if (vma && ((vma->vm_flags & VM_PFNMAP) !=3D 0)) { unsigned long start_pfn, cur_pfn; - bool writable; =20 if ((memmap->vma_base + memmap->len) > vma->vm_end) { mmap_read_unlock(current->mm); @@ -188,6 +187,7 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_= memmap *memmap) struct follow_pfnmap_args args =3D { .vma =3D vma, .address =3D memmap->vma_base + i * PAGE_SIZE, + .write_fault =3D !!(memmap->attr & ACRN_MEM_ACCESS_WRITE), }; =20 ret =3D follow_pfnmap_start(&args); @@ -197,16 +197,8 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm= _memmap *memmap) cur_pfn =3D args.pfn; if (i =3D=3D 0) start_pfn =3D cur_pfn; - writable =3D args.writable; follow_pfnmap_end(&args); =20 - /* Disallow write access if the PTE is not writable. */ - if (!writable && - (memmap->attr & ACRN_MEM_ACCESS_WRITE)) { - ret =3D -EFAULT; - break; - } - /* Disallow refcounted pages. */ if (pfn_valid(cur_pfn) && !PageReserved(pfn_to_page(cur_pfn))) { diff --git a/include/linux/mm.h b/include/linux/mm.h index 485df9c2dbdd..34c79b5fcb9b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3136,9 +3136,12 @@ struct follow_pfnmap_args { * Inputs: * @vma: Pointer to @vm_area_struct struct * @address: the virtual address to walk + * @write_fault: if true, fail with -EFAULT unless the mapping is + * writable */ struct vm_area_struct *vma; unsigned long address; + bool write_fault; /** * Internals: * diff --git a/mm/memory.c b/mm/memory.c index ff338c2abe92..40997a26846f 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6786,12 +6786,15 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, u= nsigned long address) } #endif /* __PAGETABLE_PMD_FOLDED */ =20 -static inline void pfnmap_args_setup(struct follow_pfnmap_args *args, - spinlock_t *lock, pte_t *ptep, - pgprot_t pgprot, unsigned long pfn_base, - unsigned long addr_mask, bool writable, - bool special) +static inline int pfnmap_args_setup(struct follow_pfnmap_args *args, + spinlock_t *lock, pte_t *ptep, + pgprot_t pgprot, unsigned long pfn_base, + unsigned long addr_mask, bool writable, + bool special) { + if (!writable && args->write_fault) + return -EFAULT; + args->lock =3D lock; args->ptep =3D ptep; args->pfn =3D pfn_base + ((args->address & ~addr_mask) >> PAGE_SHIFT); @@ -6799,6 +6802,7 @@ static inline void pfnmap_args_setup(struct follow_pf= nmap_args *args, args->pgprot =3D pgprot; args->writable =3D writable; args->special =3D special; + return 0; } =20 static inline void pfnmap_lockdep_assert(struct vm_area_struct *vma) @@ -6820,8 +6824,9 @@ static inline void pfnmap_lockdep_assert(struct vm_ar= ea_struct *vma) * @args: Pointer to struct @follow_pfnmap_args * * The caller needs to setup args->vma and args->address to point to the - * virtual address as the target of such lookup. On a successful return, - * the results will be put into other output fields. + * virtual address as the target of such lookup, and optionally set + * args->write_fault to require a writable mapping. On a successful + * return, the results will be put into other output fields. * * After the caller finished using the fields, the caller must invoke * another follow_pfnmap_end() to proper releases the locks and resources @@ -6844,7 +6849,8 @@ static inline void pfnmap_lockdep_assert(struct vm_ar= ea_struct *vma) * * This function must not be used to modify PTE content. * - * Return: zero on success, negative otherwise. + * Return: zero on success, -EFAULT if @args->write_fault was set but the + * mapping is not writable, -EINVAL if there is no mapping at all. */ int follow_pfnmap_start(struct follow_pfnmap_args *args) { @@ -6857,6 +6863,7 @@ int follow_pfnmap_start(struct follow_pfnmap_args *ar= gs) pud_t *pudp, pud; pmd_t *pmdp, pmd; pte_t *ptep, pte; + int r =3D -EINVAL; =20 pfnmap_lockdep_assert(vma); =20 @@ -6890,10 +6897,12 @@ int follow_pfnmap_start(struct follow_pfnmap_args *= args) spin_unlock(lock); goto retry; } - pfnmap_args_setup(args, lock, NULL, pud_pgprot(pud), - pud_pfn(pud), PUD_MASK, pud_write(pud), - pud_special(pud)); - return 0; + r =3D pfnmap_args_setup(args, lock, NULL, pud_pgprot(pud), + pud_pfn(pud), PUD_MASK, pud_write(pud), + pud_special(pud)); + if (r) + spin_unlock(lock); + return r; } =20 pmdp =3D pmd_offset(pudp, address); @@ -6911,10 +6920,12 @@ int follow_pfnmap_start(struct follow_pfnmap_args *= args) spin_unlock(lock); goto retry; } - pfnmap_args_setup(args, lock, NULL, pmd_pgprot(pmd), - pmd_pfn(pmd), PMD_MASK, pmd_write(pmd), - pmd_special(pmd)); - return 0; + r =3D pfnmap_args_setup(args, lock, NULL, pmd_pgprot(pmd), + pmd_pfn(pmd), PMD_MASK, pmd_write(pmd), + pmd_special(pmd)); + if (r) + spin_unlock(lock); + return r; } =20 ptep =3D pte_offset_map_lock(mm, pmdp, address, &lock); @@ -6923,14 +6934,16 @@ int follow_pfnmap_start(struct follow_pfnmap_args *= args) pte =3D ptep_get(ptep); if (!pte_present(pte)) goto unlock; - pfnmap_args_setup(args, lock, ptep, pte_pgprot(pte), - pte_pfn(pte), PAGE_MASK, pte_write(pte), - pte_special(pte)); + r =3D pfnmap_args_setup(args, lock, ptep, pte_pgprot(pte), + pte_pfn(pte), PAGE_MASK, pte_write(pte), + pte_special(pte)); + if (r) + goto unlock; return 0; unlock: pte_unmap_unlock(ptep, lock); out: - return -EINVAL; + return r; } EXPORT_SYMBOL_GPL(follow_pfnmap_start); =20 @@ -6972,7 +6985,11 @@ int generic_access_phys(struct vm_area_struct *vma, = unsigned long addr, int offset =3D offset_in_page(addr); int ret =3D -EINVAL; bool writable; - struct follow_pfnmap_args args =3D { .vma =3D vma, .address =3D addr }; + struct follow_pfnmap_args args =3D { + .vma =3D vma, + .address =3D addr, + .write_fault =3D !!(write & FOLL_WRITE) + }; =20 retry: if (follow_pfnmap_start(&args)) @@ -6982,9 +6999,6 @@ int generic_access_phys(struct vm_area_struct *vma, u= nsigned long addr, writable =3D args.writable; follow_pfnmap_end(&args); =20 - if ((write & FOLL_WRITE) && !writable) - return -EINVAL; - maddr =3D ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot); if (!maddr) return -ENOMEM; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 45e784462ec6..0c4ff223162b 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2939,8 +2939,11 @@ static bool vma_is_valid(struct vm_area_struct *vma,= bool write_fault) static int hva_to_pfn_remapped(struct vm_area_struct *vma, struct kvm_follow_pfn *kfp, kvm_pfn_t *p_pfn) { - struct follow_pfnmap_args args =3D { .vma =3D vma, .address =3D kfp->hva = }; - bool write_fault =3D kfp->flags & FOLL_WRITE; + struct follow_pfnmap_args args =3D { + .vma =3D vma, + .address =3D kfp->hva, + .write_fault =3D !!(kfp->flags & FOLL_WRITE), + }; int r; =20 /* @@ -2959,7 +2962,7 @@ static int hva_to_pfn_remapped(struct vm_area_struct = *vma, */ bool unlocked =3D false; r =3D fixup_user_fault(current->mm, kfp->hva, - (write_fault ? FAULT_FLAG_WRITE : 0), + (args.write_fault ? FAULT_FLAG_WRITE : 0), &unlocked); if (unlocked) return -EAGAIN; @@ -2967,17 +2970,16 @@ static int hva_to_pfn_remapped(struct vm_area_struc= t *vma, return r; =20 r =3D follow_pfnmap_start(&args); - if (r) + if (r) { + if (r =3D=3D -EFAULT) { + *p_pfn =3D KVM_PFN_ERR_RO_FAULT; + return 0; + } return r; - } - - if (write_fault && !args.writable) { - *p_pfn =3D KVM_PFN_ERR_RO_FAULT; - goto out; + } } =20 *p_pfn =3D kvm_resolve_pfn(kfp, NULL, &args, args.writable); -out: follow_pfnmap_end(&args); return r; } --=20 2.55.0