In arch/x86/mm/hugetlbpage.c:huge_pmd_share() we call find_vma(mm, addr)
and then subsequently dereference the pointer returned without checking if
it was NULL. I can't find anything that guarantees that find_vma() will
never return NULL in this case, so I believe there's a genuine bug.
However, I'd greatly appreciate it if someone would take the time to
double check me.
This patch implements what I believe to be the correct handling of a NULL
return from find_vma(). Please consider for inclusion.
Signed-off-by: Jesper Juhl <jj@xxxxxxxxxxxxx>
---
hugetlbpage.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index 069ce7c..0ebd3d0 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -61,14 +61,19 @@ static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
static void huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
{
struct vm_area_struct *vma = find_vma(mm, addr);
- struct address_space *mapping = vma->vm_file->f_mapping;
- pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
- vma->vm_pgoff;
+ struct address_space *mapping;
+ pgoff_t idx;
struct prio_tree_iter iter;
struct vm_area_struct *svma;
unsigned long saddr;
pte_t *spte = NULL;
+ if (!vma)
+ return;
+
+ mapping = vma->vm_file->f_mapping;
+ idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+
if (!vma_shareable(vma, addr))
return;
--
Jesper Juhl <jj@xxxxxxxxxxxxx> http://www.chaosbits.net/
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