Messages in this thread | | | From | Hawkins Jiawei <> | Subject | Re: [PATCH 3/3] ntfs: check overflow when iterates ATTR_RECORDs | Date | Wed, 31 Aug 2022 19:47:20 +0800 |
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On Wed, 31 Aug 2022 at 18:13, Dan Carpenter <dan.carpenter@oracle.com> wrote: > > On Wed, Aug 31, 2022 at 10:48:54AM +0800, Hawkins Jiawei wrote: > > Kernel will iterates over ATTR_RECORDs in mft record in ntfs_attr_find(). > > Because the ATTR_RECORDs are next to each other, kernel can get the next > > ATTR_RECORD from end address of current ATTR_RECORD, through current > > ATTR_RECORD length field. > > > > The problem is that during iteration, when kernel calculates the end address > > of current ATTR_RECORD, kernel may trigger an overflow bug in > > executing `a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length))`. This > > may wrap, leading to a forever iteration on 32bit systems. > > > > This patch solves it by adding an overflow checking on calculating end address > > of current ATTR_RECORD during iteration. > > > > Suggested-by: Dan Carpenter <dan.carpenter@oracle.com> > > Link: https://lore.kernel.org/all/20220827105842.GM2030@kadam/ > > Signed-off-by: Hawkins Jiawei <yin31149@gmail.com> > > --- > > fs/ntfs/attrib.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c > > index 904734e34507..55e618c9e63e 100644 > > --- a/fs/ntfs/attrib.c > > +++ b/fs/ntfs/attrib.c > > @@ -617,6 +617,9 @@ static int ntfs_attr_find(const ATTR_TYPE type, const ntfschar *name, > > return -ENOENT; > > if (unlikely(!a->length)) > > break; > > + /* check for wrap around */ > > + if ((u8 *)a + le32_to_cpu(a->length) < (u8 *)a) > > + break; > > Wouldn't it also be good to check that a + a->length <= mrec_end? > It gets checked on the next iteration sure, but it just seems like a > reasonable thing to check here. Hi Dan, Thanks for your suggestion, I will add this check in my v2 patch!
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