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x86/mm/pat: clear VM_PAT if copy_p4d_range failed 

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>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ma Wupeng 2023-02-17 10:56:15 +08:00 committed by Andrew Morton
parent a1b92a3f14
commit d155df53f3
4 changed files with 14 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
arch/x86/mm/pat/memtype.c
View File

@ -1073,11 +1073,15 @@ 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)
{
vm_flags_clear(vma, VM_PAT);
}

7
include/linux/pgtable.h
View File

@ -1191,9 +1191,10 @@ 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
@ -1205,7 +1206,7 @@ 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, bool mm_wr_locked);
extern void untrack_pfn_moved(struct vm_area_struct *vma);
extern void untrack_pfn_clear(struct vm_area_struct *vma);
#endif
#ifdef CONFIG_MMU

1
mm/memory.c
View File

@ -1290,6 +1290,7 @@ 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;
}

2
mm/mremap.c
View File

@ -683,7 +683,7 @@ 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 */