From: Ma Wupeng mawupeng1@huawei.com

[ Upstream commit d155df53f31068c3340733d586eb9b3ddfd70fc5 ]

Syzbot reports a warning in untrack_pfn(). Digging into the root we found that this is due to memory allocation failure in pmd_alloc_one. And this failure is produced due to failslab.

In copy_page_range(), memory alloaction for pmd failed. During the error handling process in copy_page_range(), mmput() is called to remove all vmas. While untrack_pfn this empty pfn, warning happens.

Here's a simplified flow:

dup_mm dup_mmap copy_page_range copy_p4d_range copy_pud_range copy_pmd_range pmd_alloc __pmd_alloc pmd_alloc_one page = alloc_pages(gfp, 0); if (!page) return NULL; mmput exit_mmap unmap_vmas unmap_single_vma untrack_pfn follow_phys WARN_ON_ONCE(1);

Since this vma is not generate successfully, we can clear flag VM_PAT. In this case, untrack_pfn() will not be called while cleaning this vma.

Function untrack_pfn_moved() has also been renamed to fit the new logic.

Link: https://lkml.kernel.org/r/20230217025615.1595558-1-mawupeng1@huawei.com Signed-off-by: Ma Wupeng mawupeng1@huawei.com Reported-by: syzbot+5f488e922d047d8f00cc@syzkaller.appspotmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Alexander Ofitserov oficerovas@altlinux.org Cc: stable@vger.kernel.org --- arch/x86/mm/pat/memtype.c | 12 ++++++++---- include/linux/pgtable.h | 7 ++++--- mm/memory.c | 1 + mm/mremap.c | 2 +- 4 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c index d5ef64ddd35e9..fd819f112a7a7 100644 --- a/arch/x86/mm/pat/memtype.c +++ b/arch/x86/mm/pat/memtype.c @@ -1108,11 +1108,15 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn, }

/* - * untrack_pfn_moved is called, while mremapping a pfnmap for a new region, - * with the old vma after its pfnmap page table has been removed. The new - * vma has a new pfnmap to the same pfn & cache type with VM_PAT set. + * untrack_pfn_clear is called if the following situation fits: + * + * 1) while mremapping a pfnmap for a new region, with the old vma after + * its pfnmap page table has been removed. The new vma has a new pfnmap + * to the same pfn & cache type with VM_PAT set. + * 2) while duplicating vm area, the new vma fails to copy the pgtable from + * old vma. */ -void untrack_pfn_moved(struct vm_area_struct *vma) +void untrack_pfn_clear(struct vm_area_struct *vma) { vma->vm_flags &= ~VM_PAT; } diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index d468efcf48f45..734d5e707fe6d 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1121,9 +1121,10 @@ static inline void untrack_pfn(struct vm_area_struct *vma, }

/* - * untrack_pfn_moved is called while mremapping a pfnmap for a new region. + * untrack_pfn_clear is called while mremapping a pfnmap for a new region + * or fails to copy pgtable during duplicate vm area. */ -static inline void untrack_pfn_moved(struct vm_area_struct *vma) +static inline void untrack_pfn_clear(struct vm_area_struct *vma) { } #else @@ -1135,7 +1136,7 @@ extern void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, extern int track_pfn_copy(struct vm_area_struct *vma); extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn, unsigned long size); -extern void untrack_pfn_moved(struct vm_area_struct *vma); +extern void untrack_pfn_clear(struct vm_area_struct *vma); #endif

#ifdef CONFIG_MMU diff --git a/mm/memory.c b/mm/memory.c index 8d71a82462dd5..95db1df5fd03a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1289,6 +1289,7 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) continue; if (unlikely(copy_p4d_range(dst_vma, src_vma, dst_pgd, src_pgd, addr, next))) { + untrack_pfn_clear(dst_vma); ret = -ENOMEM; break; } diff --git a/mm/mremap.c b/mm/mremap.c index 3a3cf4cc2c632..9457a1e06b5ae 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -668,7 +668,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,

/* Tell pfnmap has moved from this vma */ if (unlikely(vma->vm_flags & VM_PFNMAP)) - untrack_pfn_moved(vma); + untrack_pfn_clear(vma);

if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) { /* We always clear VM_LOCKED[ONFAULT] on the old vma */