On Wed, May 23, 2012 at 09:20:43AM +0200, Sasha Levin wrote:
> A missing vlidation of the value returned by find_vma() could cause a NULL ptr
> dereference when walking the pagetable.
>
> This is triggerable from usermode by a simple user by trying to read a
> page info out of /proc/pid/pagemap which doesn't exist.
>
> Introduced by commit 025c5b24 ("thp: optimize away unnecessary page table
> locking").
>
> Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
> ---
> fs/proc/task_mmu.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 3e564f0..885830b 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -820,7 +820,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
>
> /* find the first VMA at or above 'addr' */
> vma = find_vma(walk->mm, addr);
> - if (pmd_trans_huge_lock(pmd, vma) == 1) {
> + if (vma && pmd_trans_huge_lock(pmd, vma) == 1) {
> for (; addr != end; addr += PAGE_SIZE) {
> unsigned long offset;
>
> --
Thank you. I have no objection.
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
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