From: Ma Wupeng <mawupeng1@xxxxxxxxxx>
[ 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@xxxxxxxxxx
Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx>
Reported-by: <syzbot+5f488e922d047d8f00cc@xxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Alexander Ofitserov <oficerovas@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
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 */
--
2.42.1
